ChemEngineering doi: 10.3390/chemengineering10070081

Authors: Alon Davidy

Ionic liquids (ILs) are salts that are liquid at or below 100 °C. They are composed entirely of ions and have unique properties like negligible vapor pressure, high thermal stability, and tunable structures. These characteristics make them a promising alternative to traditional, often volatile and toxic organic solvents in the petrochemical industry. They have broad applications in chemical and petrochemical industry processes. Ionic liquids may be applied in the following processes: desulfurization, benzene toluene xylene (BTX) separation, alkylation, and carbon capture units. Two different ionic liquid-based process configurations have been evaluated for BTX separation. It has been found that the process configuration working with 1-ethyl-3methylimidazolium tricyanomethanide ([emim][TCM]) reduces the energy costs and capital expenditures associated with the Morphylane process by 67 and 63%, respectively. It also reduces solvent costs, confirming it as a cleaner alternative. The hydrodesulfurization (HDS) process is operated under harsh conditions, such as high temperature and high pressure and the requirement of a noble catalyst and hydrogen. High-Temperature Hydrogen Attack (HTHA) failure occurs at high temperatures between the gaseous molecular hydrogen contained inside the steel pressure vessel and the carbon atoms located in the steel matrix or in carbides. Methane molecules are produced during this reaction. This phenomenon can consequently lead to a loss of mechanical properties due to surface decarburization and to the formation of defects caused by methane bubbles mainly located at grain boundaries. The application of ionic liquids (ILs) in oil refineries offers significant advantages, such as safety, environmental sustainability, and process efficiency, primarily by serving as versatile alternatives to hazardous traditional solvents and catalysts. Across BTX extraction, carbon capture, and desulfurization/HDS-adjacent service, the recurring barriers are high viscosity, difficult regeneration, solvent cost/inventory and uncertain long-term stability.

ChemEngineering doi: 10.3390/chemengineering10070080

Authors: Zarook Shareefdeen Salma Mansour

Excessive concentrations of carbon dioxide (CO2) in the atmosphere lead to adverse environmental effects. Biologically assisted processes that rely on organisms such as microalgae (i.e., Chlorella vulgaris) are common in capturing CO2 from the atmosphere. Microalgae are rich in proteins, vitamins, minerals, and omega-3 fatty acids. Thus, microalgae production serves both health and environmental sectors. Varying light intensity and temperature are shown to influence algae growth. To quantify algae production under different light intensity and temperature conditions, and monitoring or scaling-up of biological reactors, reliable mathematical models are required. In this work, mathematical models that incorporate light intensity and temperature effects on algae growth in batch and continuous bioreactors are developed. Based on the modeling, the growth rate is maximum at Topt = 25 °C, reaching the value of μmax = 0.14 day−1. The growth rate exponentially increases until light intensity (I) reaches around 150 μmolm2s, which is approximately the optimal light intensity for Chlorella vulgaris. The effect of T on growth rate is found to be more sensitive than light intensity (I) in both batch and continuous reactor systems. When there are too many parameters in models, uncertainties exist and parameter estimation and model predictions become cumbersome. For these reasons analytical solutions to the models are presented in simplified forms and these models are more practical and easier to implement. The novelty of the work is also the presentation of the models in analytical forms. Analytical solutions to the two reactor models (batch and continuous) will help quantify biomass production as a function of time under the varying light intensity and temperature conditions encountered.

ChemEngineering doi: 10.3390/chemengineering10060079

Authors: Kevin Llopart Jie Zheng Liqun Guo Yan Yao Andrew M. Ullman Jagjit Nanda Robert L. Sacci

Halide solid electrolytes (HSE) have shown remarkable stability against high-voltage cathodes. Some HSE, such as Li3InCl6 (LIC), can be readily synthesized via aqueous routes. Here, we expand the aqueous synthesis of LIC to include Y substitution, which has different hydration coordination strengths, to form Li3InxY1−xCl6 (LIYC, 0 ≤ x ≤1). This composition is intended to combine the high ionic conductivity of LIC with the superior stability of Li3YCl6 (LYC). We compared solution-synthesized products with those derived mechanochemically. We found that adding ammonium chloride in a 3:1 ratio to YCl3 + InCl3 produces a phase-pure product, with X-ray diffraction (XRD) revealing structure similarity for both routes. Through nuclear magnetic resonance (NMR) and impedance measurements, we evaluate how the synthesis method affects ionic transport, particularly regarding correlated motion. Despite lower initial grain boundary impedance in mechanochemical samples, full cells made from solution-synthesized samples show superior cycling performance. This work establishes a scalable aqueous synthesis route for LIYC that achieves properties comparable to traditional mechanochemical methods.

ChemEngineering doi: 10.3390/chemengineering10060078

Authors: Hui Chen Yun Zheng Jingling Chen Lei Fang Bifen Gao Bizhou Lin Bo Weng Yilin Chen

The facet-dependent catalytic behavior of MgO in non-thermal plasma (NTP)-driven CO2 decomposition is systematically investigated by combining experimental measurements and density functional theory (DFT) calculations. Three MgO catalysts with dominant exposure of the (100), (110), and (111) facets are synthesized. CO2 temperature-programmed desorption (CO2-TPD) shows that CO2 adsorption capacity follows the order MgO(110) > MgO(111) > MgO(100), consistent with DFT-derived adsorption energies. DFT energy profiles reveal that although MgO(110) binds CO2 most strongly, it suffers from excessively strong CO adsorption (5.84 eV), inhibiting product desorption. In contrast, MgO(111) offers a favorable CO2 adsorption energy combined with a remarkably low CO desorption energy (0.71 eV), enabling rapid turnover. Electronic structure analyses demonstrate substantial charge transfer from MgO(111) to CO2 (up to 1.76 |e|) and pronounced orbital hybridization near the Fermi level, which are further enhanced under plasma conditions. Plasma-catalytic tests at 0.8 W show that MgO(111) achieves the highest CO2 conversion (60.7%) with excellent selectivity toward CO (95.3%) and O2 (94.4%), outperforming MgO(110) and MgO(100). Increasing the input power from 0.8 to 2.5 W raises conversion to 78.1% but reduces energy efficiency due to increased gas heating or non-productive pathways. Overall, the (111)-enriched MgO is identified as an efficient and selective catalyst for NTP-based CO2 splitting, owing to its optimal balance of adsorption strength, facile CO desorption, strong charge transfer, and plasma–catalyst synergy. This work highlights the importance of facet engineering and power optimization for designing oxide-based plasma catalysts toward energy-efficient CO2 utilization.

ChemEngineering doi: 10.3390/chemengineering10060077

Authors: Hamza Ahmad Ahmad Ali Kashif Rashid Ahmed Omer Riaz Khan Wajahat Waheed Kazmi Faysal M. Al-Khulaifi

Plasma gasification is a sustainable and advanced technology for the safe and efficient treatment of municipal solid waste (MSW). In this process, a plasma torch serves as the primary heating source to convert MSW into syngas and inert vitrified slag. The produced syngas can be used for various downstream applications, including power generation. In this study, an updraft plasma gasifier is modeled using the Aspen Plus process simulator, with municipal solid waste from Lahore, Pakistan, used as the feedstock. Air is selected as a plasma-forming gas due to its low cost and widespread availability. The primary aim of this research is to analyze the effect of specific torch power and the air-to-feed mass flow ratio on syngas molar composition, syngas higher heating value (HHV), and cold gas efficiency (CGE), and to maximize gasifier performance. CGE of the gasifier is optimized using a surrogate-based model integrated with a genetic algorithm (GA). An artificial neural network (ANN) is employed as the surrogate model for the optimization of CGE. The novelty of this work lies in two key aspects: firstly, this is among the first studies to specifically model and simulate plasma gasification of Lahore’s MSW, capturing its unique waste composition characteristics; and secondly, the integration of process simulation with a data-driven optimization framework using an ANN surrogate model. A total of 1521 data points were generated from the Aspen Plus simulation to train the ANN model and perform optimization in MATLAB. The optimized CGE was found to be 90.6%. Validation of the ANN-GA optimization was carried out by implementing the optimized input parameters in the Aspen Plus gasifier model. The resulting CGE shows a percent relative error of only 0.11% compared to the MATLAB-predicted value, confirming the accuracy of the surrogate model. Furthermore, comparison with the base case simulation reveals that the optimized operating conditions lead to an 8.6% increase in cold gas efficiency, demonstrating the effectiveness of the proposed optimization approach.

ChemEngineering doi: 10.3390/chemengineering10060076

Authors: Rashed Kaiser

The performance and durability of lithium metal solid-state batteries are governed by the dynamic evolution of the lithium/solid-electrolyte (Li/SSE) interface, where electrochemical reactions, mass transport, and mechanical constraints are intrinsically coupled. This review presents an integrated electro-chemo-mechanical framework that links interfacial stripping dynamics to distinct degradation regimes controlled by current density, stack pressure, and thermal activation. We show that stable cycling emerges only within a narrow flux-balance window in which lithium creep and vacancy diffusion compensate stripping-induced volume loss without triggering electrolyte fracture or filament penetration. By synthesizing recent experimental, modeling, and materials engineering advances, the review maps the transitions between void-dominated instability, pressure-assisted stabilization, and stress-limited failure. Particular emphasis is placed on adaptive pressure strategies, compliant interlayer design, and microstructural interface engineering as pathways to expand the operational stability window. The analysis highlights that interfacial stability is not solely a materials property but a systems-level outcome arising from coupled electro-mechanical boundary conditions and temperature-dependent transport processes. This perspective provides design principles for developing next-generation solid-state batteries capable of stable high-rate cycling and long-term reliability.

ChemEngineering doi: 10.3390/chemengineering10060075

Authors: George Catalin Tofan Catalin Andrei Tugui Alina Adriana Minea Emilian Turcanu Elena Ionela Chereches

Nanocolloid research has undergone a complete transformation, renouncing the empirical estimation of properties and relying on real case scenarios. The main objective of this paper is to compare a large number of samples that were experimentally studied in terms of thermophysical properties in order to be able to draw a conclusion in terms of the heat transfer efficiency of a certain surfactant addition to a 2 wt.% TiO2 nanoparticle-enhanced fluid. The analysis discusses both the advantages and drawbacks in terms of surfactant type and concentration influence over the Prandtl number, thermal diffusivity, and Nusselt number, as well as the heat transfer coefficient for different Reynolds numbers in laminar flow. The investigation also includes a different figure of merits and performance evaluation criteria that are extensively employed in the literature in order to have a complete overview of the efficiency of surfactants in improving nanocolloids. In conclusion, even if surfactants are considered for improving nanocolloid stability, their drawbacks have not been debated in depth in the open literature. The main conclusion that arises from this study outlines that among all tested samples, F127 at a concentration of 0.25 wt.% consistently demonstrates the best overall performance, achieving an optimal balance between enhanced thermal properties and acceptable pumping requirements.

ChemEngineering doi: 10.3390/chemengineering10060074

Authors: Sarmad Al-Anssari Dhifaf Sadeq Hassanain A. Hassan Ahmed Hamid Al-Taie Hasan Ali Abood Mohammed Mahdi Zain-Ul-Abedin Arain

Oil recovery from carbonate reservoirs is one of the critical challenges in the oil industry due to the strongly oil-wet nature, natural fractures, and the heterogeneity of carbonate rocks. Subsequently, waterflooding can only displace oil from large fractures, leaving the majority of oil trapped in the rock matrix. This work suggests that nanofluid flooding, as a predesigned flooding method, is an alternative to conventional waterflooding. Various concentrations of silica nanofluid at different nanoparticle concentrations were formulated and systematically investigated for their characteristics, stability at reservoir conditions, and their influence on wettability and oil recovery. Silica nanoparticles were sustainably synthesized from waste materials to ensure the feasibility and environmental friendliness of the process. Results indicated that the synthesized silica has an amorphous crystalline nature characterized by nano-sized particles. Additionally, treating silica nanoparticles with a silane group significantly enhances the stability of nanofluids in a high-salinity environment. Most interestingly, by comparing the amount of oil recovered, the results revealed that implementing nanofluid flooding as a secondary oil recovery, rather than waterflooding, can produce around 12% more oil, in addition to eliminating a whole waterflooding step. This is the first study to alter the traditional flooding scenario and directly conduct nanofluid flooding as secondary oil recovery, without being preceded by waterflooding, using sustainably synthesized nanoparticles. Considering the water crisis in the Middle East, this approach can save substantial amounts of water, which improves the sustainable development of communities.

ChemEngineering doi: 10.3390/chemengineering10060073

Authors: Serhiy Pyshyev Mariia Shved Yurii Lypko Anatolii Hordiienko

The production of inexpensive, effective sorbents from natural materials for the purification of water bodies and/or soils is a pressing problem. Therefore, the purpose of this manuscript is to summarize current approaches to the use of brown coal (lignite) and its processing products (humic acids, HAs) as sorbents for the purification of aqueous and soil environments from heavy metal ions and other pollutants. Modification of lignite (chemical, biological, physicochemical) or the creation of lignite–mineral composites significantly increases its sorption capacity and stability: after modification, the sorption capacity can reach more than 85 mg of heavy metals per g of sorbent, which is only 3 times lower than that of specialized, expensive sorbents. Also, good results are achieved in the case of sorption of water-soluble organic drugs, dyes, etc. Humic acids obtained from brown coal have better selectivity and efficiency than the original lignite, and slightly worse than the modified one, in terms of removing cadmium, lead, copper, and other toxic elements; and also, can complex with organic xenobiotics. Current research trends indicate growing interest in multifunctional composite sorbents, environmentally friendly extraction technologies, and the development of materials with enhanced selectivity and regeneration ability. Future studies should focus on improving the understanding of sorption mechanisms, optimizing modification strategies, scaling up lignite-based technologies for practical environmental applications, and developing waste-free technologies to produce sorbents from lignite.

ChemEngineering doi: 10.3390/chemengineering10060072

Authors: Mozhgan Hosseinnezhad Alireza Mahmoudi Nahavandi Sohrab Nasiri

The production of sustainable and cost-effective energy remains a global challenge, with photovoltaic technology emerging as a promising solution. Sensitizers play a key role in electron production in dye-sensitized solar cells, which are emerging photovoltaic devices; thus, different chemical structures have been introduced to achieve the best results. Determining the optimal conditions for the coating and application of dye materials to obtain optimal efficiency and performance is of great importance. For this purpose, an organometallic dye was used to extract the optimal coating conditions. Two factors—ambient temperature during photoanode preparation and anti-aggregation agent concentration—were selected as effective parameters, and the optimal conditions for achieving high efficiency and durability were determined using machine learning. Finally, the findings were analyzed from two perspectives: the preparation of laboratory devices using the selected dye and the evaluation of similar dye materials to validate the proposed optimal conditions.

ChemEngineering doi: 10.3390/chemengineering10060071

Authors: Marcin Przybylak Marta Kaczmarek Agnieszka Dutkiewicz Hieronim Maciejewski

Cotton fabrics are widely used due to their comfort and biodegradability; however, their intrinsic hydrophilicity limits their performance in advanced applications. In this work, a fluorine-free approach for imparting durable hydrophobicity to cotton was developed based on thiol-ene crosslinking of polysiloxane networks formed on the fiber surface. Two thiol-functional polysiloxanes differing in –SH group content were combined with four vinyl-functional organosilicon crosslinkers under UV (2,2-dimethoxy-2-phenylacetophenone (DMPA)) and thermal (2,2′-azobis(2-methylpropionitrile) (AIBN)) initiation. FT-IR analysis confirmed the presence of siloxane structures, while SEM-EDS revealed stable silicon- and sulfur-containing layers. SEM observations showed continuous coatings without blocking the textile structure. Water contact angle (WCA) measurements demonstrated that hydrophobic performance strongly depends on thiol content and crosslinker structure, with the highest values obtained for the thiol-rich polysiloxane and tetrafunctional vinyl crosslinker. All modified fabrics exhibited high durability, with minimal changes in WCA and complete droplet stability (1800 s) after washing. In the case of the lower-functionality polysiloxane, an increase in hydrophobicity after washing was observed, attributed to the reorganization of siloxane chains. These results demonstrate that thiol-ene crosslinking provides an effective strategy for designing durable, fluorine-free hydrophobic coatings on cotton.

ChemEngineering doi: 10.3390/chemengineering10060070

Authors: Giulia Ciattaglia Paolo Di Gianvincenzo Sergio E. Moya Isabelle Navizet Marco D’Abramo

Here, we present a general statistical-mechanical model able to reconstruct the temperature dependence of the thermodynamic properties of non-covalent host–guest inclusion complexes using a set of molecular dynamics simulations along an isobar. Our approach, applied to β-cyclodextrin in interaction with E- and Z-dimethomorph as well as a bisphenol A derivative, provides a robust description of the in silico data, able to well reproduce the host–guest binding thermodynamics at every temperature.

ChemEngineering doi: 10.3390/chemengineering10060069

Authors: Xinyu Wang Xiangming Zhao Hao Wan Fengqiang Miao Dongdong Ren Jianxiang Guo Siyi Luo Feng Xu

Among the various CO2 capture technologies, chemical absorption is currently one of the most widely applied methods in industrial practice. In this study, density functional theory was employed to investigate the reaction mechanisms of CO2 absorption by typical alkanolamine solvents. Reaction pathways between CO2 and four representative alkanolamines—monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), and methyldiethanolamine (MDEA)—were constructed and analyzed. By evaluating the activation energy barriers of different amines, the thermodynamic characteristics and reaction feasibility of the CO2 absorption process were systematically elucidated. The results show that the primary amine MEA exhibits the lowest activation energy barrier (32.02 kJ/mol), indicating the most favorable reaction kinetics, while the secondary amine DEA shows a slightly higher barrier of 47.35 kJ/mol. As tertiary amines, TEA and MDEA exhibit significantly higher activation energy barriers, indicating slower reaction kinetics; however, they generally possess higher CO2 loading capacities and less stable reaction products, which facilitate solvent regeneration. The activation energy barriers of MDEA and TEA were calculated to be 54.53 kJ/mol and 94.17 kJ/mol, respectively, indicating that MDEA reacts more readily with CO2 than TEA.

ChemEngineering doi: 10.3390/chemengineering10060068

Authors: Nujud Badawi Ashraf Khalifa

This study aims to develop a sustainable, low-cost, and high-performance supercapacitor electrode by valorizing waste date seeds (Phoenix dactylifera) into activated carbon and integrating it with a polymer-based hydrogel electrolyte. Waste date seeds were successfully converted into high-performance activated carbon through hydrothermal carbonization followed by sulfuric acid (H2SO4) chemical activation. The obtained date seed activated carbon (DSAC) was applied as an electrode material and incorporated into a hydrogel electrolyte for supercapacitor applications. Structural, thermal, and morphological analyses using SEM, FTIR, XRD, and TGA confirmed the formation of a predominantly microporous carbon framework enriched with oxygen-containing functional groups, indicating effective carbonization and activation. The porous structure and surface chemistry contributed to enhanced electrochemical behavior. The electrochemical behavior of the prepared DSAC electrode was investigated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analyses. The material exhibited a highest specific capacitance of 179 F g−1 at a scan rate of 5 mV s−1 and 159 F g−1 at a current density of 0.2 A g−1, demonstrating reliable and stable capacitive characteristics suitable for biomass-derived carbon-based supercapacitor applications. The device also exhibited excellent cycling stability over 5500 cycles, confirming long-term durability. The results demonstrate a promising and environmentally friendly strategy for advanced energy storage systems. Furthermore, the sustainability and cost-effectiveness of the proposed approach are attributed to the utilization of abundant date seed biomass and the simplicity of the hydrothermal–chemical activation process. The enhanced electrochemical performance is primarily associated with the hierarchical porous structure of the activated carbon and the improved ion transport facilitated by the hydrogel electrolyte, which collectively contribute to stable capacitive behavior and long-term cycling durability.

ChemEngineering doi: 10.3390/chemengineering10050067

Authors: Anca Chelmuș Mihaela Constantin Nicolae Băran

Cyclone separators remain widely used for gas–solid separation, yet analytical prediction of cut size and pressure drop remains challenging. This study presents an explicit semi-empirical model for the cut size (d50) of reverse-flow cyclones based on the radial particle equation of motion in cylindrical coordinates, with d50 obtained by equating radial migration time and residence time. A closed-form solution is derived in the Stokes regime, whereas non-Stokes behavior is handled numerically through the Schiller–Naumann drag correction. Turbulence is incorporated through a phenomenological correction, and the grade–efficiency curve is represented by a logistic relation. The model was implemented in MATLAB R2025a and applied in a parametric study covering inlet velocity, particle density, cyclone diameter, and gas viscosity. A Euler-type pressure drop relation was included to examine the separation–energy trade-off. Validation on the Kim et al. benchmark using one calibration point per cyclone family and six independent verification cases yielded a mean absolute percentage error of 13.5% and a root mean square error of 0.22 μm for d50; the paired pressure drop check gave a 2.8% mean absolute percentage error. A complementary benchmark based on Wang et al. using 15 cm 1D3D and 2D2D cyclones under actual-air and standard-air conditions further supported the family-calibrated use of the model. A separate scale-up test showed that constant swirl intensity similarity is not transferable across large diameter changes. The formulation provides a transparent reduced-order tool for preliminary design and sensitivity analysis.

ChemEngineering doi: 10.3390/chemengineering10050066

Authors: Sofianos Panagiotis Fotias Eirini Maria Kanakaki Afzal Memon Anna Samnioti Jahir Khan John Nighswander Vassilis Gaganis

Differential Liberation Expansion (DLE) and viscosity tests are core elements of the Pressure–Volume–Temperature (PVT) laboratory suite used to characterize reservoir oils under depletion and to support compositional modeling and reservoir simulation. Nevertheless, both DLE and viscosity testing remain expensive and time-consuming due to specialized equipment, strict operating procedures, and the need for experienced laboratory personnel. Building on our prior work that introduced the proximity-informed Local Interpolation Model (LIM) framework for Constant Composition Expansion (CCE), this study demonstrates how the same end-to-end, neighborhood-based workflow is applied to DLE and viscosity test data. A target fluid is embedded in a compositional–thermodynamic descriptor space and paired with a small set of thermodynamically similar fluids drawn from a PVT data archive. Within this locality, LIM is used to infer DLE behavior by combining local interpolation for key scalar quantities (e.g., saturation-point and endpoint PVT values) with shape-preserving reconstruction of pressure-dependent curves. For viscosity, the same approach reconstructs the oil viscosity curve μop across the undersaturated and saturated regions. Evaluation on a proprietary database of DLE and viscosity tests shows strong agreement across diverse fluids for both DLE and oil viscosity trends. For example, across Tier 1–3 fluids, the mean curve mean absolute percentage error (MAPE) is 1.01% for Bo, 0.51% for ρo, and 1.32% for the liberated-gas Z-factor, while the conditioned baseline viscosity workflow yields a mean diphasic-branch MAPE of 7.75%. This supports reducing reliance on new DLE and viscosity measurements while maintaining engineering-grade fidelity in reservoir engineering and simulation workflows. This approach has been fully automated through software so it can be set up and directly utilized by the field operators on their own databases to significantly reduce their fluid sampling and laboratory analysis costs. Moreover, the proposed (artificial intelligence) AI model does not use others’ data, respecting data privacy and data ownership.

ChemEngineering doi: 10.3390/chemengineering10050065

Authors: Peyman Alizadeh Mahtab Sultany Sarah Chen Taylor Wright Preksha Sharma Xiaotao Bi

This study examines how catalysts and operating conditions enhance the pyrolysis of textile wastes, supporting their use as a viable feedstock for waste-to-energy recycling. Pyrolysis of three common textile wastes—cotton, polyester, and nylon—was studied using thermogravimetric analysis (TGA). Experiments were conducted at heating rates of 5, 10, 15, and 20 °C/min, both with and without catalysts, including K2CO3, ZnO, KOH, CaO, and natural zeolite. The results showed that cotton decomposes at significantly lower temperatures than polyester and nylon, with a peak decomposition rate at 361.7 °C compared to 437.9 °C for polyester and 459.8 °C for nylon. Reaction kinetics were analyzed using three established models: Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Kissinger. Among the materials studied, polyester exhibited the lowest activation energy (184.8 kJ/mol), while cotton and nylon showed higher values (241.1 and 236.2 kJ/mol, respectively). Catalyst performance varied by material. Potassium carbonate was particularly effective for cotton, increasing the weight loss rate and reaction rate constant. ZnO significantly reduced the activation energy for nylon. Although catalysts generally enhanced reaction rates, many also increased activation energy. This increase in activation energy and collision frequency suggests that catalytic pyrolysis becomes more temperature-sensitive while achieving higher reaction turnover frequencies.

ChemEngineering doi: 10.3390/chemengineering10050064

Authors: Ramonna I. Kosheleva Agni Moutzouroglou Ioanna Tsolakidi Pigi-Varvara Liouni Eleni Noula Eleni Koumlia Athanasios C. Mitropoulos

The effect of high-gravity fields, generated by rapid rotation, on CO2 adsorption in activated carbon beds is examined. Adsorption-desorption kinetics is monitored before, during, and after short rotation periods at up to 5000 rpm. Rotation induced a reproducible transient bump in headspace pressure, quantitatively attributed to a centrifugal free energy shift (~12.2 J/mol) that overfilled weak adsorption sites beyond their static equilibrium. The bump mechanism is described by fold catastrophe theory, with a critical angular velocity (ωc = 3500 rpm) triggering a sudden transition to a high-occupancy branch. Post-rotation, constant-rate zero-order desorption from shallow sites overlapped with a slower pseudo-first-order adsorption process as deep, previously inaccessible pores became available, increasing CO2 capacity by 2.5%. Kinetic modeling produced an apparent diffusivity of 1.2 × 10−5 m2/s and a structural accessibility time constant of ~25 h. Thermodynamic analysis showed that rotation improved the overall free energy of adsorption and altered entropy in a manner consistent with the observed adsorption-desorption sequence. These results demonstrate that rotational fields can enhance CO2 uptake, modify kinetic pathways, and trigger threshold phenomena in porous adsorbents.

ChemEngineering doi: 10.3390/chemengineering10050063

Authors: Ieva Kiminaitė Mindaugas Aikas Sebastian Wilhelm Vilmantė Kudelytė Rita Kriūkienė Arūnas Baltušnikas Irena Vaškevičienė Andrius Tamošiūnas

This study investigated the influence of hydrocarbon feedstock composition evolved from slow pyrolysis of polypropylene (PP) and polystyrene (PS) and plasma gas flow rate on the carbon black and hydrogen production yields and quality. The temperature distribution and feedstock flow within the carbon black formation zone with plasma were supplementarily modeled using computational fluid dynamics. TG-FTIR-GC/MS was employed to analyze thermal degradation patterns of plastics and to estimate the composition of volatile intermediates of plastics’ slow pyrolysis. Produced CB was characterized, encompassing physical, structural, and compositional properties using thermogravimetric analysis, CHNS analysis, scanning electron microscopy–energy dispersive spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller, and Raman spectroscopy. The results revealed that both feedstocks yield CB with comparable structural characteristics; however, PS-derived (aromatic-rich) volatiles produce significantly higher CB yields, whereas PP-derived (aliphatic) volatiles favor hydrogen formation. Differences in carbon structure were also observed, with PP-derived CB exhibiting a higher degree of graphitic ordering compared to the more disordered CB obtained from PS. The optimal flow rate of plasma gas was identified as 6.1 L/min. Increasing the flow rate to 7.2 L/min led to reduced conversion efficiency for PP-derived long-chain hydrocarbons. Overall, the findings demonstrate the potential of this approach for the co-production of high-quality carbon black and hydrogen from plastic waste.

ChemEngineering doi: 10.3390/chemengineering10050062

Authors: Tim van Schagen Wim Brilman

In this paper, a flexible steady-state model of a highly integrated, natural convection-driven condensing methanol reactor was developed. The flowsheet model includes 1D submodels of the different sections of the integrated reactor–condenser and includes a method to estimate the maximum possible natural convection-driven flow. Experimental data are used to create a shortcut description for the heat transfer coefficients in the model. The model results indicate that when heat losses can be mitigated, autothermal operation is possible. The major part of the heat integration takes place in the economizer section; however, a significant amount of heat transfer occurs at the catalyst bed also. The model predicts that the loop mass flow and single-pass conversion strongly depend on the catalyst bed inlet temperature. Experimentally measured catalyst preheater and condenser duties suggest, however, that the model-calculated mass flow is likely too low and that it is less dependent on the catalyst bed inlet temperature than the model predicts. A possible cause for this is the neglect of radial temperature gradients in the catalyst bed in the model, overestimating the conversion. Another possible cause is a measurement error in the bed inlet temperature, causing the actual temperature to be lower than the measured value. Natural convection calculations show that the maximum achievable flow strongly depends on the single-pass conversion and that given a single-pass conversion, a minimum temperature difference is required for flow in the right direction. Sensitivity analyses (neglecting heat losses to the environment) show that with the current heat transfer description, the feasible operating range for autothermal, natural convection-driven flow is sizeable. However, at lower recycle mass flows, heat transfer is too fast, leading to premature condensation in the economizer section. If the heat transfer coefficient is smaller than the currently predicted value, autothermal operation is possible in a wide range of conditions. If heat losses are mitigated, the maximum productivity of 2000 kgMeOHmcat.−3h−1 is achievable at high pressure, a moderate catalyst bed inlet temperature and a low condenser temperature.

ChemEngineering doi: 10.3390/chemengineering10050061

Authors: Lamia Boulafrouh Stéphanie Boudesocque Aminou Mohamadou Laurent Dupont

This study presents an innovative approach for the selective extraction of Co(II) and its separation from Ni(II) using ethyl ester glycine–betaine derivatives, specifically tri(n-pentyl)[2-ethoxy-2-oxoethyl]ammonium dicyanamide, as extractants in combination with continuous-mode liquid–liquid contact. Semi-pilot-scale implementation requires non-equilibrium conditions, characterized by short contact times between effluent and extractant phases. To address this, we propose dissolving analog of glycine–betaine ionic liquid (AGB-IL) in low-viscosity MIBK solvents to enhance mass transfer while reducing dependence on fossil-based solvents. Liquid–liquid extraction and continuous-flow stripping experiments were designed based on prior batch results and conducted in a saline environment, employing a chaotropic electrolyte for extraction and a kosmotropic electrolyte for stripping. Both open and closed systems were tested to compare extractive performance with batch conditions and with scenarios representative of industrial operations. Results indicate that continuous-flow systems achieve performance comparable to batch systems in terms of extraction efficiency, Co/Ni separation coefficients, and recyclability. These findings provide proof of concept for the development of semi-pilot and pilot-scale processes for efficient cobalt recovery.

ChemEngineering doi: 10.3390/chemengineering10050060

Authors: M. S. L. Manasa S. F. León-Luis A. Muñoz P. Rodríguez-Hernández J. Ruiz-Fuertes V. Monteseguro

The stability of the competing orthorhombic Pnma and monoclinic P21/c phases of Praseodymium pentaphosphate (PrP5O14) have been studied using density functional theory (DFT). At 0 K, the Pnma structure is found to be preferred over the P21/c one with the enthalpy change with pressure of both phases highlighting a shift in phase preference from Pnma to P21/c at ∼2.5 GPa. Independently of the predicted high-pressure structural phase transition at 0 K, our computed elastic properties and phonon dispersion bands as a function of pressure indicate a phonon instability at ∼4.5 GPa due to the appearance of imaginary frequencies, followed by a dynamical instability at 8.5 GPa due to the violation of the Born criteria on the Pnma structure of PrP5O14. These results eliminate the orthorhombic structure as a possible high-pressure candidate for the monoclinic P21/c polymorph. Furthermore, the relative stability of the orthorhombic and monoclinic polymorphs has been evaluated at ambient pressure and as a function of temperature by means of vibrational free-energy calculations. The results indicate a free-energy crossing at 42 K, with the Pnma phase being energetically favored from 0 K to 42 K, after which the P21/c phase becomes preferred. These results demonstrate why PrP5O14 can only be obtained at ambient pressure in the monoclicnic P21/c polymorph, different to other rare earth pentaphosphates.

ChemEngineering doi: 10.3390/chemengineering10050058

Authors: Sarmad Ahmad Qamar Aneela Basharat Simona Piccolella Severina Pacifico

The depletion of natural resources has emerged as a major global concern, accelerating the transition from petroleum-based to renewable materials. The development of biobased ‘active’ materials is emerging especially in food packaging to ensure safety and functionality. Such packaging systems containing bioactive ingredients provide effective antioxidant, antimicrobial, and UV-protective features extending food shelf life. In this context, plant-derived secondary metabolites have gained substantial interest as functional reinforcements. These compounds not only provide food protection but also contribute to environmental safety owing to their inherent biocompatibility, biodegradability, and compostability. However, their high production costs remain a major challenge to large-scale applications. Therefore, the valorization of agro-food byproducts/wastes has been increasingly promoted. This review aims to discuss the combined use of plant secondary metabolites and biopolymers for the development of innovative packaging solutions, highlighting recent advances and functional performance. Furthermore, key challenges limiting their real-world applicability are addressed. In particular, the intrinsic hydrophilicity of many biobased materials compromises their moisture barrier and mechanical stability. To overcome this limitation, the use of biobased hydrophobic ingredients including natural waxes has emerged as a sustainable and effective approach to enhance water resistance while preserving the bioactive functionality of the packaging materials.

ChemEngineering doi: 10.3390/chemengineering10050059

Authors: Mansour Boukthir Narimen Chakchouk Lahcen Fkhar Abdelfattah Mahmoud Abdallah Ben Rhaiem

K-ion batteries (KIB) are considered the future energy storage and conversion technology due to their remarkable performance. In this work, a high-temperature solid-state process was used to effectively synthesize KMnO2, a promising cathode material for KIBs. The materials were examined using X-ray powder diffraction (XRPD), Raman and infrared spectroscopies, electron microscopy analysis, optical, and impedance spectroscopies. Rietveld refinement of X-ray diffraction data confirmed that the compound crystallizes in the monoclinic system with the P-21/m space group. Fourier transform infrared and Raman spectroscopies revealed the vibrational modes of the KMnO2 compound and proved the existence of the octahedral environment MO6 (M = Mn, K), which affirms structural configuration. The morphological distribution and grain size of the titled compound were examined using SEM studies. A direct band gap of around 3.12 eV was found by optical studies using UV–Vis spectroscopy, confirming the semiconducting nature of KMnO2 and indicating its applicability for optoelectronic and energy-related applications. The characteristics of this material were further examined using impedance spectroscopy at temperatures between 343 and 443 K and a frequency range of 10−1 Hz to 106 Hz. The DC conductivity and relaxation time exhibited Arrhenius behavior, with a significant shift in activation energy at 373 K, suggesting a change in the conduction mechanism. The frequency behavior of AC conductivity, σac, was analyzed using the universal Jonscher law. The findings of the charge transportation study on KMnO2 indicate that this material follows a non-overlapping small polaron tunneling (NSPT) for T < 383 K and correlated barrier hopping (CBH) above for T > 383 K. A correlation between the ionic conductivity and the crystal structure was established and discussed.

ChemEngineering doi: 10.3390/chemengineering10050057

Authors: Intisar Ul Hassan Meshari Ahmed M AlZahrani Ruaa AlaEldin Ageeb Abakar Zia Ur Rahman Aniz Chenampilly Ummer Usama Ahmed Mohammad Nahid Siddiqui Abdul Gani Abdul Jameel

This research systematically investigated the catalytic pyrolysis of Arab Heavy (AH) and Arab Light (AL) crude oils using NiO supported on Al2O3 or ZSM-5 in a microwave-assisted reactor, with particular emphasis on hydrogen (H2) generation and value-added chemicals. To understand how both the catalyst and feedstock affect reaction products, gas and liquid products as well as catalyst activity were carefully examined. The production of H2 and olefins was significantly enhanced by the NiO/Al2O3 catalyst, especially when using AL crude. This is most likely due to favorable metal-support interactions that increase the dehydrogenation activity. However, when paired with lighter feedstock, NiO/ZSM-5 greatly increased paraffin production and encouraged light alkane synthesis in both phases. GC-MS and FTIR spectroscopy confirmed that NiO/Al2O3 produced liquid products richer in aromatics while also containing a significant fraction of paraffins. Remarkably, the AL over NiO/Al2O3 combination showed very little liquid recovery, indicating that gas generation was higher in these reaction conditions. These results showed how H2 selectivity and hydrocarbon routes in NiO/ZSM-5 and NiO/Al2O3 are controlled by various microwave-catalyst interactions. This work further highlights the importance of matching catalyst properties with feedstock type to control product selectivity, with NiO/Al2O3 showing particular promise for H2-focused applications.

ChemEngineering doi: 10.3390/chemengineering10050056

Authors: Ahmed Hosney Marius Urbonavičius Šarūnas Varnagiris Ilja Ignatjev Johanna Bolaños-Zuñiga Donata Drapanauskaitė Sana Ullah Karolina Barčauskaitė

Optimizing chitosan recovery from shrimp shells is one of the most effective measures in shrimp waste management. Incorporating machine learning-based models will significantly impact the optimization process. This research aimed to evaluate the optimization of chitosan extraction from Litopenaeus vannamei shrimp shells using deproteinization and exploratory machine learning-based similarity model approaches. Chitosan extraction from shrimp shells was optimized using a deproteinization method, where various NaOH concentrations (1, 2, 3, 4, 5, and 10%) were applied at room temperature (RT) and 50 ± 2 °C, while maintaining controlled conditions for demineralization and deacetylation. The chitosan products were characterized by ash content, moisture, yield percentage, deproteinization efficiency, FTIR, deacetylation degree (DD), XRD, crystallinity index (CI%), and scanning electron microscopy (SEM). A machine learning random forest regressor model was developed to evaluate the similarities between the laboratory-synthesized and commercial chitosan (CC) samples. The results confirmed the formation of chitosan with semi-complete deacetylation (DD% from 98.84 ± 0.1% to 99.27 ± 0.004%). Deproteinization efficacy was in the range of 93.39 ± 0.083% to 97.0 ± 0.31%. XRD and SEM analyses demonstrated that commercial chitosan (CC) possessed a predominately amorphous structure, whereas the isolated chitosan samples exhibited low crystallinity, with increased amorphism at higher NaOH concentrations and temperatures. The machine learning-based similarity model indicated that Ch3 and Ch4 samples exhibited the highest resemblance degrees to commercial chitosan, while the S1 sample showed the lowest similarity. However, most of the recovered chitosan samples showed low similarity to commercial chitosan; they retained their higher degree of deacetylation (DD%), structural integrity, and quality parameters, indicating the success of the deproteinization route in enhancing chitosan production.

ChemEngineering doi: 10.3390/chemengineering10040054

Authors: Sergey Gusarov Svetlana Sapelnikova Julio J. Valdes Anguang Hu Stanislav R. Stoyanov

This work proposes a general conceptual framework for integrating TRIZ (Theory of Inventive Problem Solving) structured reasoning into large language model (LLM)-based workflows for chemical and materials science. We argue that persistent AI challenges in this domain—data scarcity, weak scaffold transferability, unphysical predictions, and limited interpretability—are most naturally framed as TRIZ-style contradictions and that embedding contradiction-resolution logic into LLM reasoning can elevate AI from pattern-matching to inventive, researcher-like problem solving. Unlike prior AI–TRIZ integrations such as AutoTRIZ and TRIZ-GPT, which address general engineering tasks, the present framework extends TRIZ tools to physicochemical phenomena and targets local, privacy-preserving deployment. To illustrate the concept and identify directions for further development, we implement and evaluate a simplified three-stage proof-of-concept pipeline on nine local LLMs across eleven chemical problems. Results show that the TRIZ-guided pipeline substantially reduces token consumption—both overall and especially in the solution-generation stage—without an obvious loss in solution quality under the adopted evaluation criteria, suggesting considerable room for further improvement as the framework matures.

ChemEngineering doi: 10.3390/chemengineering10040055

Authors: Dong-Ham Wu Rome-Ming Wu

In this work, hydrocyclones with a diameter of 45 mm and cone lengths of 85 mm and 110 mm were employed to investigate the classification behavior of silicon carbide particles. Numerical simulations were carried out using FLUENT based on computational fluid dynamics (CFD). The internal flow characteristics were modeled using the Volume of Fluid (VOF) approach for multiphase flow, coupled with the Large Eddy Simulation (LES) turbulence model. Furthermore, the Discrete Phase Model (DPM) was applied to track particle trajectories and analyze their dynamic behavior within the hydrocyclone. The experimental results showed that, under identical inlet pressure conditions, the hydrocyclone with a cone length of 110 mm achieved superior separation efficiency. Increasing the cone length leads to a reduction in cone angle, which contributes to improved classification performance. However, practical design constraints limit the extent to which the cone length can be increased. To further explore this effect, an extended cone geometry of 150 mm was investigated through numerical simulation. The CFD results indicate that a longer cone structure enhances air core stability, prolongs particle residence time, and decreases the probability of particle misclassification. These findings suggest that optimizing cone length is an effective strategy for improving hydrocyclone performance. The novelty of this study lies in the integration of experimental validation and numerical simulation to systematically evaluate both practical and extended cone designs, thereby providing deeper insights into the relationship between structural parameters and separation efficiency.

ChemEngineering doi: 10.3390/chemengineering10040053

Authors: Regina Fuchs-Godec

The corrosion protection of copper in acidic urban rain environments was studied using self-assembled hydrophobic layers (SAHLs) based on stearic acid (SA), with and without rosehip seed oil (RH). The limited durability of fatty acid-based self-assembled layers under acidic conditions was addressed by correlating surface wettability, morphology, and electrochemical behaviour. Contact angle and SEM analyses showed that SA alone forms a moderately hydrophobic but structurally irregular layer, whereas the addition of 2.0 wt.% RH produces a hierarchical micro/nanostructure with near-superhydrophobic characteristics (CA ≈ 149°). Electrochemical measurements in simulated acid rain solutions (pH 5, 3, and 1) revealed a strong pH dependence of protective performance. While SA-derived layers provided effective protection at pH 5, they deteriorated at lower pH due to protonation of carboxylate anchoring groups and electrolyte ingress. In contrast, SAHLs containing 2.0 wt.% RH maintained polarisation resistance in the MΩ cm2 range and inhibition efficiencies above 99% at pH 3, and remained effective even at pH 1. Long-term EIS results indicate a predominantly diffusion-controlled, barrier-type inhibition mechanism associated with defects sealing and interfacial reorganisation. Notably, the rosehip seed oil used is a commercially available, bio-based material with expired shelf life, highlighting the potential of waste-derived resources for sustainable corrosion protection.

ChemEngineering doi: 10.3390/chemengineering10040052

Authors: Qi Zhang Linlin Zhang Xinkuan Zhao Ke Xu Zili Chen Yanliang Ji

Aqueous organic flow batteries are a promising technology for large-scale energy storage, owing to their safety, low cost, and tunable molecular properties. Battery performance is critically governed by the redox potential, solubility, and stability of organic active species, making molecular design a central research priority. Yet, many current systems still rely on inorganic metal-based materials, which face challenges such as high cost and sluggish kinetics. This review outlines a systematic molecular-engineering framework for designing novel redox species, offering strategies to tailor solubility, redox potential, and molecular size in both organic compounds. Recent advances in mechanistic insight, functionalization, and structure-dependent electrochemical performance are summarized. Computational chemistry and machine learning are highlighted for accelerating high-throughput screening and property prediction, speeding up molecular optimization. Small molecules (1–4 rings), including quinones (C=O), alloxazines, phenazines, and indigo derivatives, which undergo reversible redox reactions involving nitrogen and/or carbonyl groups, have been explored as anolytes and/or catholytes in aqueous redox flow batteries. Key challenges remain, including limited electrochemical stability windows, insufficient solubility, and poor molecular stability, leading to low energy density and cycling degradation. Improving anolyte performance by simultaneously lowering redox potential and enhancing solubility and stability is therefore crucial for advancing both organic and broader redox-active battery systems. Computational and machine learning approaches for identifying and refining electrolyte molecules are also addressed, enabling efficient screening and molecular modification toward high-performance flow batteries.

ChemEngineering doi: 10.3390/chemengineering10040051

Authors: Bartosz Libecki Regina Wardzyńska Marzanna Kurzawa Zuzanna Achcińska

Textile industry wastewater poses a significant environmental challenge due to the presence of persistent dyes. Cationic dyes are characterized by resistance to the conventional coagulation method. The appropriate properties and combination of chemicals guarantee an effective removal process. This study explains the effect of modification of methylene blue solution by the addition of a natural biopolymer—hydrolyzed tannic acid (TA). The study assumed that a combination of tannic acid, methylene blue and polyaluminum chloride would provide a synergistic effect and significantly improve the coagulation and sediment filtration process. Coagulation tests were carried out for a range of methylene blue concentrations. The optimal arrangement of solution components and coagulant doses was selected and tested. Over 95% dye removal efficiency was achieved. The maximum dye removal efficiency was determined to be 5 mg/mg Al at pH = 5.0. Based on the analysis of UV-VIS spectroscopy, FTIR and electrokinetic potential, changes in the solutions of tannin-modified dyes and their effect on the precipitation of flocs and the nature of sorption were determined. The main phenomena affecting the removal mechanism are discussed. The results indicate that tannic acid can serve as a sustainable coagulant aid, supporting the development of technologies for treating cationic-dye-laden wastewater.

ChemEngineering doi: 10.3390/chemengineering10040050

Authors: Awal Adava Abdulsalam Ayobamiji Charles Idowu Sabina Khabdullina Zhamilya Sairan Yersain Sarbassov Madina Pirman Dilnaz Amrasheva Elizabeth Arkhangelsky Tri Thanh Pham Stavros G. Poulopoulos

In this study, a waste-to-resource route for water remediation is presented by supporting Pd and Cu nanoparticles (NPs) on hydrochar (HC) derived from spent coffee grounds (SCG). Unlike conventional noble-metal catalysts, HC was first produced via hydrothermal carbonization of SCG, followed by a completely green, tannic acid-assisted reduction step that simultaneously deposits Pd and Cu NPs without toxic reductants or organic solvents. The resulting catalysts were evaluated for catalytic reduction of 4-nitrophenol (4-NP) and for antibacterial activity against Escherichia coli (E. coli; BL21) and Staphylococcus aureus (S. aureus), including biofilm inhibition. Among formulations, the bimetallic catalyst containing approximately equal proportions of Pd and Cu (HC@Pd0.5Cu0.5) achieved the fastest 4-NP reduction, completing the reaction in ~3 min, with an apparent first-order rate constant of 1.35 min−1 and a total turnover frequency of 483.6 h−1. Notably, Cu incorporation enhanced antibacterial performance, with the Cu-rich variant (HC@Pd0.25Cu0.75) achieving the strongest inhibition (MICs of 1.25 mg/mL against E. coli and 2.5 mg/mL against S. aureus) and effective biofilm suppression. This dual-action catalyst, derived entirely from waste through green methods, advances circular-economy principles and green chemistry by simultaneously tackling chemical pollutants and microbial contaminants in water, thereby contributing to SDG 6 (Clean Water and Sanitation).

ChemEngineering doi: 10.3390/chemengineering10040049

Authors: Sungmin Na Hyunjin An Kwangjin Park

Layered sodium transition-metal oxides are promising cathode materials for sodium-ion batteries due to their high theoretical capacity; however, their practical application is often limited by sluggish Na+ diffusion kinetics and structural instability during cycling. P2/O3 phase coexistence has been proposed as an effective strategy to balance capacity and stability, yet it is typically achieved through precise Na-content tuning or complex synthesis conditions, which restrict compositional flexibility. Herein, we demonstrate a phase-engineering approach that induces stable P2/O3 phase coexistence without adjusting the overall Na stoichiometry by controlling the dopant incorporation pathway. Using Na0.8(Ni0.25Fe0.33Mn0.33Cu0.07)O2 (NaNFMC) as a model system, Mg doping via a wet chemical route enables homogeneous dopant distribution, which triggers local stacking rearrangement and the formation of prismatic Na+ diffusion channels characteristic of the P2 phase. In contrast, dry-doped samples with identical Mg content retain a predominantly O3-type structure, highlighting the decisive role of dopant incorporation in governing phase evolution. As a result of the phase-engineered P2/O3 coexisting framework, the Mg wet-doped cathode exhibits enhanced initial reversibility, superior rate capability, and improved long-term cycling stability compared to pristine and dry-doped counterparts. Voltage-resolved dQ/dV and cyclic voltammetry analyses reveal stabilized redox behavior with reduced polarization, while electrochemical impedance spectroscopy confirms suppressed impedance growth and improved Na+ transport kinetics after cycling. This study establishes that phase engineering through controlled dopant incorporation provides an effective alternative to conventional Na-content tuning strategies for layered sodium cathodes. The findings offer a scalable and versatile design principle for optimizing the electrochemical performance and structural durability of next-generation sodium-ion battery cathode materials.

ChemEngineering doi: 10.3390/chemengineering10040048

Authors: Abdoulah Ly Ndeye Bineta Dia Mamadou Faye

Fermentation is a promising sustainable and ecofriendly alternative for producing high-added-value chemicals such as 2,3-butanediol (2,3-BDO). The emergence of process analytical technology (PAT) tools, combined with advances in chemometrics, enables real-time process monitoring of product attributes, thereby ensuring quality. The aim of this study is to transfer near-infrared (NIR) partial least squares (PLS) models under two scenarios for the monitoring of 2,3-BDO production. PLS regression models initially developed under specific conditions were transferred across domains using dynamic orthogonal projection (DOP) and domain invariant (di)-PLS standard-free calibration transfer (CT) methods. For the 1st scenario involving model transfer from “mock samples” to “flask atline,” di-PLS was able to enhance NIR PLS model performance with improvements in RMSEC and RMSEP of 18 and 25% (2 g/L absolute error), respectively. In the 2nd scenario, however, DOP successfully transferred the model from the “flask atline” domain to the “500 mL bioreactor online” domain, achieving RMSEC and RMSEP values of 12 and 14 g/L, respectively. The feasibility of multivariate model transfer for PAT applications in complex fermentation systems from atline to online configurations using standard-free CT methods is demonstrated. This enhances model adaptability under varying conditions, fostering process scale-up and real-time monitoring.

ChemEngineering doi: 10.3390/chemengineering10040047

Authors: Sofianos Panagiotis Fotias Eirini Maria Kanakaki Vassilis Gaganis Anna Samnioti Jahir Khan John Nighswander Afzal Memon

Constant Composition Expansion (CCE) experiments provide critical relative-volume and density information describing the thermodynamic behavior of reservoir oils and gases under varying pressure. These properties are vital inputs for hydrocarbon reservoir engineering, as they impact how oil and gas move through the reservoir during production. However, the need for specialized personnel, high-end equipment and measures taken to ensure safety in handling high pressure fluids often render the CCE experiments expensive and slow. This work introduces a Local Interpolation Method (LIM), a proximity-informed, end-to-end CCE fluid properties prediction Artificial Intelligence (AI) model that leverages domain expertise and synthetic Pressure–Volume–Temperature (PVT) data archives that mimics the actual data. The AI model generates surrogate CCE behavior for new fluids, thereby reducing the need for completing laboratory CCE measurements when sufficiently similar fluids exist in the available archive and neighborhood support is strong. Each new fluid is embedded in a compositional–thermodynamic descriptor space, and its response is inferred from a small neighborhood of thermodynamically similar fluids. Within this locality, the LIM combines hybrid local interpolation for key scalar properties (such as saturation-point quantities and expansion endpoints) with shape-preserving reconstruction of monophasic and diphasic relative-volume curves, enforcing continuity at saturation and consistency between relative volume, density and compressibility. The workflow operates purely at inference time and does not require case-specific retraining. Application to a curated archive of CCE tests shows that LIM reproduces key CCE features with very good agreement to existing data across a range of fluid types, indicating that proximity-based AI modeling can substantially reduce reliance on new CCE experiments while maintaining engineering-useful agreement for compositional simulation workflows. Under leave-one-out evaluation on 488 CCE tests, mean curve-level Mean Absolute Percentage Error (MAPE) is 0.07% for monophasic relative volume and 0.07% for monophasic density. For well-supported neighborhoods (Tiers 1–3, n = 376), mean MAPE is 0.04% for both, with 2.65% for derived compressibility and 1.78% for diphasic relative volume. The workflow is automated in software to facilitate reproducible inference on operator-owned archives and can reduce turnaround time and laboratory burden in well-supported neighborhoods. The proposed AI model uses available experimental data owned by each operator and does not use others’ data while respecting the data privacy and data ownership.

ChemEngineering doi: 10.3390/chemengineering10040046

Authors: Gema Gil-Muñoz Juan Alcañiz-Monge

This study evaluates the performance of Ni-La2O3/Beta catalysts for the dry reforming of methane, focusing on the effects of nickel loading, catalyst pretreatment, reaction temperature, and gas composition and flow rate. Catalysts with nickel contents ranging from 3 to 20 percent by weight were prepared via wet impregnation and characterized by gas adsorption, X-ray diffraction, temperature-programmed reduction with hydrogen, thermogravimetric analysis, and transmission electron microscopy. The results indicate that nickel gradually incorporates into the zeolitic support, preferentially occupying the most stable sites. Direct reduction of the impregnated catalyst precursors—omitting the calcination step—yielded materials with slightly higher methane conversion (ca. 3.5%) and enhanced stability. This improved performance is attributed to the reduction occurring during the thermal decomposition of supported nickel nitrate, which promotes finer nickel dispersion and stronger interaction with the La2O3-modified Beta zeolite.

ChemEngineering doi: 10.3390/chemengineering10040045

Authors: Alejandro Jiménez Alexander Misol Antonio Gil Miguel Ángel Vicente

Aluminum is the most used non-ferrous metal, with a well-established recycling procedure, but this process also produces new residues. We recently proposed an integrated laboratory practice based on the recovery of aluminum from the slag generated during its recycling. Now, we expand upon this research by proposing the preparation of a layered material, namely hydrocalumite, from recovered Al3+. The synthesis of this solid, its characterization, and the use of the mixed oxides produced after its calcination for the photocatalytic removal of ibuprofen from aqueous solutions are structured as a laboratory practice for students in the last years of Chemistry, Chemical Engineering, Environmental Engineering, Materials Engineering, and related university or masters degrees. In this way, the work integrates material synthesis and characterization procedures with a practical introduction to catalysis photodegradation, incorporating key concepts of the Circular Economy and Sustainable Development Goals, and educating students with respect to the environment.

ChemEngineering doi: 10.3390/chemengineering10040044

Authors: Mohammed A. Salih Mohammed Ahmed Shehab Maryam Y. Ghadhban Khalid T. Rashid Mahmood Alhafadhi Ali A. Abdulabbas Adnan A. AbdulRazak

This study investigates the optimization of fabrication and operating parameters for poly(ether sulfone) (PES) ultrafiltration membranes embedded with Bismuth tungstate and multi-walled carbon nanotubes (MWCNTs) Bi2WO6/MWCNTs for the removal of dye pollutants from wastewater. Response surface methodology (RSM) coupled with Analysis of Variance (ANOVA) was employed to develop regression models for evaluating membrane performance in terms of dye rejection and permeate flux. A central composite design (CCD) was used to conduct a systematic series of ultrafiltration experiments. The effects of key variables, including Bi2WO6/MWCNTs loading (0–0.1 wt.%), operating pressure (5–9) bar, and methyl red (MR) dye concentration (50–150 ppm), on membrane separation performance were comprehensively examined. The developed models demonstrated strong statistical significance and accurately described the experimental data. Optimization results revealed that the operating parameters exerted a more pronounced influence on membrane performance than fabrication variables. The maximum MR rejection of 96.8457% was achieved at an optimal Bi2WO6/MWCNTs loading of 0.08 wt.%, dye concentration of 112.6 ppm, and operating pressure of 9 bar. Experimental validation confirmed the reliability and predictive capability of the proposed models. In order to provide high-performance membranes with enhanced permeability, antifouling resistance, and dye removal efficiency for useful wastewater treatment applications, this study attempts to optimize the operating and preparation parameters for adding Bi2WO6/MWCNT nanocomposites into PES membranes.

ChemEngineering doi: 10.3390/chemengineering10040043

Authors: Fanny Adabel González-Alejo Areli Carrera-Lanestosa Mario Moscosa-Santillán Ricardo García-Alamilla Jesús Alfredo Araujo-León Diakaridia Sangaré Juan José Acevedo-Fernández Pedro García-Alamilla

Cocoa pod husk (CPH), a major agro-industrial residue, contains valuable bioactive compounds whose recovery can support sustainable waste valorization. This study evaluated the influence of increasing ethanol concentrations on the ultrasound-assisted extraction (UAE) of bioactive compounds from CPH and their antioxidant, antihypertensive, and antihyperglycemic activity. Dried and milled CPH was extracted using ethanol–water mixtures (0–100% ethanol) under fixed ultrasonic conditions. Cocoa pod husk powder characterization and the resulting extracts were analyzed in terms of chemical composition (lignocellulosic compounds, proximate and elemental composition, and bromatological composition), antioxidant capacity, and in vivo antihypertensive and antihyperglycemic effects in Wistar rats. The results showed that solvent polarity strongly modulated extraction efficiency: absolute ethanol yielded the highest phenolic (171.43 mg GAE/g) and flavonoid (132.05 mg QE/g) content, whereas hydroalcoholic mixtures, particularly 50:50, enhanced overall antioxidant performance, especially in FRAP. The chemical analysis results showed the selective recovery of compounds such as quercetin, hesperidin, and theobromine, and FTIR-PCA results revealed distinct solvent-dependent chemical profiles. In vivo assays indicated modest blood pressure stabilization and a more pronounced antihyperglycemic effect after chronic administration. Overall, UAE proved an effective, rapid, and solvent-efficient method for CPH valorization, highlighting its potential for producing natural antioxidants applicable to food, nutraceutical, and cosmetic formulations.

ChemEngineering doi: 10.3390/chemengineering10030042

Authors: Rita Maji Joydev De

Metal-free electrodes are essential to promote electrochemical reactions, the core of sustainable energy resources. In search of better carbon-based electrode materials, we have explored several spatial arrangements of boron (B) within proximity in the graphene lattice, as evident in recent experimental observations. Multi-boron substitution enriches sites by tuning electronic structure and strengthens binding of key intermediates of oxygen reduction, oxygen evolution, and hydrogen evolution reactions facilitating electrocatalytic performance. Our optimal B-doped site shows near thermo-neutral H adsorption (ΔGH*∼±0.4eV), consistent with experiments. The overpotentials are highly sensitive to the dopant motifs and the spread among configurations shows that experimentally accessible multi-B doping can serve as a practical active site engineering knob to achieve optimized multi-functional performance. In parallel, we find that specific multi-B configurations selectively capture and pre-activate NOx (NO/NO2) under ambient conditions while retaining weak affinity for NH3. These sites also interact with SO2 and related hazardous species, enabling selective air filtration and targeted NOx control within the electrocatalytic scope of this study.

ChemEngineering doi: 10.3390/chemengineering10030041

Authors: Viktor Kalman Michael Harasek

Pressure swing adsorption (PSA) is a viable method for separating hydrogen from gas mixtures, an important aspect of long-term hydrogen storage in depleted gas fields. This study explores optimizing a 12-step PSA process for recovering high-purity hydrogen from varying compositions of hydrogen–methane mixtures, simulating the conditions likely encountered during hydrogen storage and recovery. Step-time optimization was performed on four different hydrogen–methane mixtures using the toPSAil simulation package—an open-source dynamic PSA simulator developed by researchers at the Georgia Institute of Technology—integrated with a particle swarm optimization (PSO) algorithm. The goal was to develop an optimization framework that can reliably identify PSA step times for different operating scenarios and satisfy specified purity and recovery constraints under fluctuating wellhead feed conditions. The optimization converged within 25–30 iterations, even in high-contaminant, low-pressure scenarios, where PSA performance is traditionally weak. The product purity in the optimized cycles was above 99.1% with more than 80% recovery for all cases, while fuel cell quality (99.7%) hydrogen was achieved in two out of the four scenarios. The purge-to-feed ratio of the best-performing cycles was between 0.07 and 0.32. These findings show the potential of the proposed approach in overcoming the difficulty of designing PSA cycles for non-constant gas compositions and achieving a hydrogen purification process suitable for variable feed conditions. The workflow generates a large synthetic dataset that can support surrogate or hybrid modeling. The results can help advance research in other gas separation areas with non-constant conditions, like flue gas or biogas purification.

ChemEngineering doi: 10.3390/chemengineering10030040

Authors: María Lorena Malagón-Quinto Hilda Elizabeth Reynel-Ávila Didilia Ileana Mendoza-Castillo Adrián Bonilla-Petriciolet Norma Aurea Rangel-Vázquez Gloria Sandoval-Flores Sarah Essam

This review analyzes the catalytic routes for the Power-to-X (PtX) conversion of hydrogen to methane, methanol, ammonia, formic acid, and synthetic hydrocarbon fuels. The key reactive synthesis technologies and catalysts for each vector are described. Recent studies and pilot projects summarizing the reaction pathways of each vector and the associated catalyst technologies are also discussed. The analysis indicates that catalyst selection critically influences the efficiency and selectivity of these reactive systems. Some catalyst synthesis routes rely on expensive critical minerals (e.g., Ru and Rh), which raise technical and economic challenges for their industrial application. Catalyst deactivation and scale-up limitations are also relevant issues to be resolved. Emerging catalysts (e.g., Fe–Co or Co–Ni bimetallics, core–shell materials, metal-organic frameworks (MOFs), electrides, covalent-organic frameworks (COFs), and perovskites) are being explored to enhance stability, selectivity, and deactivation. Europe leads PtX development to consolidate the industrial production of hydrogen-based vectors with strong policy support, while the industrial initiatives in Latin America are limited (for instance, Chile’s green methanol and ammonia projects are examples) despite its great potential to generate renewable energy. In summary, Power-to-X can store renewable energy and close the carbon loop; however, its industrial consolidation demands catalyst innovation and supportive regulatory frameworks to overcome the challenges highlighted in this review.

ChemEngineering doi: 10.3390/chemengineering10030039

Authors: Kyungbin Park Hyeonseok Im Gyu Ryeol Baek Mino Woo

This study numerically investigates the NO removal performance of a staged catalyst substrate employed in an industrial marine after-treatment system. The computational domain is based on the lab-scale experimental device used for measuring pressure drop, serving as a digital twin to accurately reproduce the staged catalyst configuration prior to its application in full-scale industrial reactors. Experiments were conducted to estimate the parameters for a porous model, employed for efficient computation of flow and reactive mass transfer inside the catalyst substrate without needing a complex computational mesh of the monolith structure. A reaction mechanism from the literature was modified and verified for marine SCR reactors. The three-dimensional numerical simulations in this study indicate that the NO removal in the staged catalyst substrate varies depending on the catalyst configuration, primarily due to differences in the upstream flow uniformity. This study demonstrates that relocating a single catalyst substrate to the downstream position improved conversion by 6.5 percentage points, while a two-stage catalyst configuration yielded a 15.5 percentage-point increase under identical exhaust conditions. In addition, the residence time exhibited significant variations depending on the catalyst arrangement and inlet velocity, highlighting it as a critical parameter governing NO reduction performance. The findings in the present study can serve as a reference for future analyses conducted under practical conditions in industrial-scale marine SCR systems.

ChemEngineering doi: 10.3390/chemengineering10030038

Authors: E. S. Manju Basavaraju Manu

Paint manufacturing wastewater contains complex mixtures of solvents, resins, surfactants, pigments, and polymeric additives that result in high chemical oxygen demand (COD), toxicity, and poor biodegradability. Conventional physicochemical treatment provides limited removal of dissolved organics, and the pollutant-level behavior of paint effluents during biological treatment remains insufficiently characterized. This study addresses this gap by evaluating a sequential anaerobic–aerobic batch process treating three distinct synthetic paint wastewater samples. This study is a comparative investigation of sequential biological treatment across multiple paint wastewater variants, combined with high-resolution LC–MS to track compound-level transformations. Treatment performance was assessed through COD removal, biogas generation, pH and redox behavior, and LC–MS profiling of organic contaminants. The anaerobic stage achieved 70–95% COD removal depending on wastewater type. Aerobic polishing increased overall removal efficiencies, while PWW3 exhibited reduced stability during extended operation. LC–MS analysis showed substantial decreases in the number and intensity of chromatographic peaks and demonstrated degradation of phthalates, glycol ethers, organophosphate plasticizers, and solvent-derived compounds. The study provides integrated performance- and pollutant-level assessment of sequential anaerobic–aerobic treatment of paint wastewater and demonstrates the influences of wastewater heterogeneity in biological degradation pathways.

ChemEngineering doi: 10.3390/chemengineering10030037

Authors: Vasile Gheorghe Dan Cristian Cuculea Eliza Chircan

This study investigates the fatigue failure of fiber-reinforced rubber used in automotive shock-absorbing elements subjected to cyclic loads. A quantitative simulation model integrated with material analysis to predict the service life and performance decay of these viscoelastic dampers was introduced. Failure is governed by a degradation factor that models accumulating fatigue damage and results in a predictable, cyclic loss of maximum force capacity; specifically, the model accurately predicts a 36.3% reduction in peak force (from 111.44 N to 70.97 N) over the first 10 fatigue cycles. Crucially, the model incorporates the non-linear stiffness behavior caused by a fiber pull-out mechanism, which transitions load resistance from high elastic integrity to lower frictional forces post-critical displacement. These findings establish a direct, quantitative link between microstructural failure (verified via SEM) and observed performance decay, offering key insights for maintenance planning and material selection.

ChemEngineering doi: 10.3390/chemengineering10030036

Authors: Konstantinos Anthopoulos Stefanos Michailidis Zafeiro Thomaidou Lydia Vogiatzaki Nikolaos C. Kokkinos

This comprehensive review provides a consolidated and practically oriented overview of the Friedel–Crafts reaction in pharmaceutical synthesis, bringing together data from 93 peer-reviewed studies published between 1962 and 2025. Through a structured and comparative analysis of the literature retrieved from the Scopus and PubMed databases, this work integrates scattered information into a single, accessible resource, designed to guide researchers in drug discovery and development. The findings identify alkylation and acylation as the dominant Friedel–Crafts transformations, often enabling the synthesis of pharmacologically relevant scaffolds depending on substrate structure and the efficiency and selectivity of the catalytic system. These include compounds with anticancer, anti-inflammatory, and antimicrobial potential. Trends in catalyst and solvent selection highlight both the persistent reliance on classical Lewis acids in chlorinated media and a gradual interest in more sustainable alternatives, although their adoption remains system-dependent. By consolidating 63 years of research into a unified reference, this review underscores the versatility and enduring relevance of Friedel–Crafts methodologies in medicinal chemistry but also offers a data-driven foundation for their optimized and more sustainable application in future pharmaceutical development.

ChemEngineering doi: 10.3390/chemengineering10030035

Authors: Timur-Vasile Chis Monica Tegledi Laurentiu Prodea Alina Maria Faladau Sadigov Murat Mammadov Elmir Anamaria Niculescu Iolanda Popa Tiberiu Sandu

Predicting CO2 absorption behavior in aqueous amine systems is a critical challenge for optimizing carbon capture technologies. This research develops a high-precision Artificial Neural Network (ANN) to simulate equilibrium data across various amine classes, including primary (MEA, DGA), secondary (DEA, DPA), and tertiary (MDEA) amines. The model architecture utilizes a Multi-Layer Perceptron (MLP) trained on a dataset split into 70% training, 15% validation, and 15% testing segments to prevent overfitting and ensure reliable generalization. By employing a Sigmoid activation function, the network achieved a coefficient of determination (R2) exceeding 0.98 and an absolute average relative deviation (AARD) below 5%. Furthermore, this study evaluates the efficacy of classical isotherms (Langmuir, Freundlich, and Temkin) strictly as empirical curve-fitting correlations for liquid-phase behavior. Results indicate that while these models are traditionally surface-adsorption based, the Langmuir form provides a mathematically robust fit for the tertiary amine MDEA (R2 = 0.9673). Experimental observations indicate that Monoethanolamine (MEA) maintains the highest capacity for CO2 uptake. Since the model relies on categorical descriptors for amine types, it offers a rapid and efficient framework for assessing specific solvents in post-combustion capture infrastructure.

ChemEngineering doi: 10.3390/chemengineering10030034

Authors: Haval Kukha Hawez Jaidon Jibi Kurisinkal Taimoor Asim

The intermittency of renewable-based power is a major barrier for long-term supply of clean energy, which necessitates the development of reliable solutions for clean energy storage and transition towards a carbon-neutral economy. Although hydrogen has emerged as a promising clean energy carrier to address this, its high compressibility requires safe, efficient and practical storage technologies for widespread deployment. Surface storage technologies for hydrogen have garnered attention due to their mobile and stationary applications, paving the way for a future hydrogen-based economy. This review provides a comprehensive review of surface hydrogen storage technologies, covering metal hydrides, metal-organic frameworks (MOFs), liquid organic hydrogen carriers (LOHCs), glass microspheres, capillary arrays, etc. Where previous reviews mostly address the chemistry behind these storage technologies, this study highlights practical integration and techno-economic assessment. Comparative analysis reveals that while LOHC and hydrides dominate in Technology Readiness Level, MOFs and carbohydrate-based systems offer high gravimetric potential, though they are currently quite costly. Other challenges like thermal management and large-scale regeneration remain critical for practical deployment. Moreover, recent advancements in Artificial Intelligence and Machine Learning offer unique insights, demonstrating their growing role in material screening, performance prediction, and the optimization of storage system designs. This review outlines the key challenges and research pathways required to support future deployment.

ChemEngineering doi: 10.3390/chemengineering10030033

Authors: Xiaosong Wang Mojtaba Koosha Tianduo Li Yinghua Gong Vladimir A. Vinokurov

While Saccharomyces cerevisiae (baker’s yeast) offers a safe, non-animal source of chitin-glucan (CG), its potential as a functional cosmetic ingredient has been overshadowed by industrial sources like Aspergillus niger. This study advances the existing literature by establishing a critical structure–function relationship for CG micro/nano particles extracted via three physical disruption methods: ultrasonic bath, ultrasonic probe, and autoclaving. The obtained CG was systematically characterized by physicochemical and biological tests. A significant trade-off was identified: while autoclaving (40 min) resulted in lower mass yield compared to ultrasonication, it produced particles with the highest crystallinity, an enriched chitin/glucan ratio, and the smallest particle size (~70% of particles with mean diameter of 480 ± 33 nm). Structurally, these sub-micron particles demonstrated superior colloidal stability and a physical “barrier effect” for sustained hydration, outperforming the amorphous structures typically associated with mild extraction. The anti-wrinkle efficacy was validated through a specific “triad” mechanism: (1) the insoluble 3D network ensures prolonged water retention, (2) the particles exhibit robust free radical scavenging activity (~67%), and (3) most notably, the specific nano-structure significantly upregulated Collagen Type I-α1 expression in human dermal fibroblasts (HDF) and human skin fibroblasts (HSF), surpassing commercial chitin controls. These findings prove that the extraction-induced nano-structure, rather than mass yield, is the determinant factor for bioactivity, positioning S. cerevisiae CG as a high-performance, multi-target ingredient for anti-aging formulations.

ChemEngineering doi: 10.3390/chemengineering10030032

Authors: Abbas H Hasan Shara K Mohammed Buddhika Hewakandamby Faiza Saidj Abdelwahid Azzi Barry James Azzopardi

Many of the film thickness measurements that have been reported in the literature tend to focus on small pipe diameters, which may not be practical for a variety of industrial applications. Additionally, single-point measurements are unable to provide the necessary film thickness data around the circumference of the pipe as well as in the axial direction. This paper aims to experimentally study the behaviour of wavy liquid films, including wave frequency, wave velocity, wave width, and wave spacing. A Multi-Pin Film Sensor (MPFS) was used to extract the thickness of a free-falling liquid film in axial, circumferential, and temporal coordinates. The range of liquid Reynolds number ReL used was 618–1670. It was found that the power spectral density of the disturbance waves showed a pronounced peak at the modal frequency of 6–8 Hz. The number of disturbance waves was found to be almost independent of ReL. The axial interfacial wave seemed to travel at a constant velocity while the mean velocity in circumferential direction was negligible. The mean width of the disturbance waves was approximately 17.7% of the pipe diameter.

ChemEngineering doi: 10.3390/chemengineering10020031

Authors: Mirel Glevitzky Gabriela-Alina Dumitrel Ana-Maria Pană Gerlinde Iuliana Rusu Mihai-Teopent Corcheş Mihaela Laura Vică

The valorization of waste cooking oils (WCOs) provides a strategy to reduce environmental impact while converting residues from the food industry into valuable products. This study developed and characterized antimicrobial soaps from purified WCOs (sunflower, palm, and pumpkin oils) enriched with natural bioactive ingredients. WCOs were purified by filtration, treatment with 10% NaCl, and bleaching with 3% H2O2, followed by cold saponification with NaOH. Twelve soap formulations were prepared, including six enriched with bee products (propolis, poly-floral honey, linden, acacia, honeydew, and sunflower) and six enriched with essential oils (EOs) (clove, rosemary, mace, nutmeg, white pepper, and juniper). The WCOs, natural bioactive ingredients, and soaps were characterized using physico-chemical methods (FTIR, GC-FID, phenols, flavonoids, etc.), while their antibacterial activity was determined against two microbial strains: Staphylococcus aureus and Escherichia coli. The antimicrobial activity of soaps is related to their alkaline pH, while the addition of honey, propolis, or EOs contributes to additional antimicrobial effects. Among honey- and propolis-enriched soaps, those with propolis produced the largest inhibition zones (up to 8.67 mm for S. aureus and 7.0 mm for E. coli). EO-based soaps exhibited higher activity, with rosemary EO-based soap showing the largest zones (up to 9.5 mm for S. aureus and 7.5 mm for E. coli). These data support the potential of enriched soaps containing honey, propolis, and EOs for antimicrobial applications, highlighting their value as a sustainable alternative in the valorization of WCOs.

ChemEngineering doi: 10.3390/chemengineering10020030

Authors: K. Pavithra Paromita Chakraborty

In the recent years, several studies from developing economies have reported the presence of per- and polyfluoroalkyl substances (PFAS) in water bodies, with perfluorooctanoic acid (PFOA) predominating, a potential endocrine disruptor. In this study, an engineered sugarcane bagasse biochar–chitosan composite (SBCT) was designed, synthesized, and evaluated as a novel adsorbent for the removal of PFOA from aqueous systems at concentrations up to 500 ppb. Batch adsorption experiments were conducted to investigate the effects of initial PFOA concentration, contact time, pH, adsorbent dosage, and temperature. Scanning electron microscopy (SEM) showed that SBCT has a significant porous structure. The composite showed over 90% of PFOA removal from water. Further, peaks corresponding to C–F bonds observed after adsorption by Fourier transform infrared (FTIR) spectroscopy confirms the adsorption of PFOA on SBCT. The protonated amine groups (NH3+) in chitosan enhanced the adsorption of anionic PFOA through electrostatic attraction with carboxyl groups (COO−). The kinetic study revealed that pseudo-first-order best described the adsorption process, with an equilibrium adsorption capacity (qeq) of 2.78 mg/g, suggesting that physisorption is the predominant mechanism. The Langmuir Isotherm model gave the best fit, establishing a maximum adsorption capacity (qmax) of 9.08 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous and exothermic, consistent with physisorption. The regeneration capacity of the SBCT composite demonstrated exceptional reusability over five methanol adsorption–desorption cycles. The adsorption kinetics, equilibrium behavior, and regeneration efficiency suggest that SBCT is a viable low-cost adsorbent for batch adsorption-based treatment systems targeting PFOA removal, particularly in decentralized and resource-constrained water treatment applications.

ChemEngineering doi: 10.3390/chemengineering10020029

Authors: Tatiana A. Moiseeva Inna Yu. Bogush Oleg I. Il’in Alexey N. Yatsenko Rajathsing Kalusulingam Tatiana N. Myasoedova

In this study, we investigated the electrochemical properties and performance characteristics of CoxSy and silicon–carbon-based heterostructures synthesized on nickel foam substrates for energy storage applications. Cobalt sulfide films were successfully electrodeposited on nickel foam (NF) using cyclic voltammetry (CV) from the solutions with different Co2+ concentrations. The presence of a silicon–carbon sublayer promotes the deposition of cobalt sulfide material. The amorphous phase of α-CoS was observed by the X-ray diffraction technique. Raman spectroscopy confirmed the formation of CoS and CoS2 phases. A significant increase in electrode areal capacitance is observed with the silicon–carbon film sublayer from 0.5 to 1.3 F·cm−2 and from 1.6 to 2.3 F·cm−2 at 3 mA·cm−2 for samples prepared from solutions with CoCl2·6H2O concentrations of 0.005 M and 0.02 M, respectively. In the case of gravimetric capacitance, an increase is observed in the presence of a silicon–carbon sublayer for the SiC@CoS_0.005 sample, rising from 690 F·g−1 to 748 F·g−1 at 4 A·g−1. Conversely, the SiC@CoS_0.02 sample shows a decrease from 1287 F·g−1 to 6590 F·g−1. It was shown that the capacitance of all the electrodes derives from the mix of diffusion-controlled and surface-controlled capacitance processes. The electrochemical impedance spectroscopy (EIS) analysis indicates that the formation of heterostructure materials significantly alters the electrochemical properties by reducing both Rf and Rs.

ChemEngineering doi: 10.3390/chemengineering10020028

Authors: Lucas Paul Andrew S. Paluch

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a global health burden, particularly due to multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. Rifampicin, a frontline anti-TB drug that inhibits RNA polymerase, has been central to therapy, but rpoB mutations compromise its efficacy. This highlights the need for Rifampicin analogues that target alternative enzymes to sustain therapeutic effectiveness. In this study, a structure-based computational approach was employed to screen Rifampicin analogues against enoylacyl carrier protein reductase (InhA), a validated enzyme in the biosynthesis of mycolic acids. A library of 399 analogues was retrieved from SwissSimilarity and evaluated using ADMET analysis, with the best candidates showing favourable pharmacokinetic profiles and compliance with Lipinski’s Rule of Five. Molecular docking identified ZINC000013629834 (−10.90 kcal/mol) and ZINC000253411694 (−10.36 kcal/mol) as superior to Rifampicin (−9.05 kcal/mol), with ILE21, SER20, and THR196 consistently stabilizing interactions. Molecular dynamics simulations confirmed the stability of the complexes, with RMSD values of 0.167 nm, 0.175 nm, and 0.297 nm for ZINC000013629834, ZINC000253411694, and Rifampicin, respectively. MM/PBSA analysis showed comparable binding free energies. These findings suggest that optimized Rifampicin analogues targeting InhA may overcome rpoB-associated resistance and serve as promising leads for next-generation anti-TB drug development.

ChemEngineering doi: 10.3390/chemengineering10020027

Authors: Jana Šic Žlabur Margareta Đumbir Anamarija Peter Jona Šurić Sandra Voća Martina Skendrović Babojelić Filip Varga Mia Dujmović

Hazelnut (Corylus avellana L.) shells, typically discarded as agro-industrial by-products, represent a potentially valuable source of bioactive polyphenolic compounds with significant antioxidant properties. This study aimed to evaluate and compare the polyphenol composition and antioxidant capacity of the kernels and shells of two hazelnut varieties, ‘Rimski’ and ‘Istarski duguljasti’. High-intensity ultrasound-assisted extraction (UAE) was applied to enhance the recovery of bioactive compounds under optimized conditions (80% ethanol, high amplitude, and 25 min treatment). The extracts were analyzed for total polyphenols, total flavonoids, total non-flavonoids, and individual phenolic compounds. Hazelnut shells exhibited significantly higher levels of total polyphenols, flavonoids, and antioxidant capacity compared to kernels. The dominant individual polyphenolic compounds identified in the shell were kaempferol, gallic acid, naringin, rutin trihydrate, quercetin-3-glucoside, chlorogenic acid, quercetin, ferulic acid, rosmarinic acid, and vanillic acid. Application of UAE notably improved extraction efficiency and overall yield compared to conventional extraction methods. The findings underscore hazelnut shells as a nutritionally and functionally valuable by-product and confirm UAE as a green, efficient extraction technique. These results provide a strong basis for developing high-value-added products for the cosmetic, pharmaceutical, and food industries, thereby supporting circular bioeconomy and sustainable chemistry principles.

ChemEngineering doi: 10.3390/chemengineering10020026

Authors: Shu-Yao Zhang Xue-Min Wang En-Peng Deng Ya-Ni Zhang Hui Zhu Qiang Chen Si-Wen Pan Yu-Xin Miao

In this study, a series of Ag/Co-HA catalysts were synthesized using a plasma-assisted method. Plasma is a partially ionized gas composed of electrons, ions, neutral molecules, free radicals, photons, and excited-state substances, which can serve as a highly reactive medium for catalyst modification. Its unique discharge characteristics can effectively regulate the dispersion of active sites, electronic structure, and metal–support interactions. The study compared the performance of catalysts prepared by the traditional high-temperature calcination method with those treated by rapid plasma in the toluene oxidation removal reaction. The results showed that the catalyst treated by dielectric barrier discharge (DBD) plasma exhibited excellent low-temperature catalytic activity, achieving 100% toluene conversion and approximately 75% CO2 selectivity at 275 °C, while the catalyst prepared by traditional calcination only achieved 73% toluene conversion and approximately 50% CO2 selectivity at 285 °C. This study provides a simple preparation method for the Ag/5Co-HA-P catalyst. Due to the plasma treatment’s ability to precisely control the catalyst structure, along with advantages such as low energy consumption, short processing time, and environmental friendliness, it holds significant application prospects in the field of VOCs treatment.

ChemEngineering doi: 10.3390/chemengineering10020025

Authors: Aygun Zabit Aliyeva Ulviyya Aliman Karimova Sahib Gadji Yunusov Michael Vigdorowitsch Sevinj Abdulhamid Mammadkhanova

Selective functionalisation of inert C(sp3)–H bonds in alkanes and cycloalkanes remains one of the main challenges in the field of environmentally sustainable chemistry. This review provides a critical assessment of current catalytic strategies, in particular addressing the persistent problem of overoxidation and low selectivity. Going beyond traditional compartmentalised summaries, this work identifies a significant trend towards the integration of non-traditional activation methods, including ultrasonic cavitation, photocatalysis, and nanosecond pulse discharges, in both homogeneous and heterogeneous systems. Key contributions include a comparative analysis of radical control strategies, in particular highlighting how intermediate hydroperoxides can be used to shift reaction pathways towards selectivity of over 97% for alcohols and ketones. In addition, we discuss the emerging role of carbon nanomaterials (e.g., fullerenes and brominated nanotubes) as active electron-rich carriers and catalysts that lower the energy barriers for C–H activation under mild, ‘green’ conditions. The review concludes that the future of scalable hydrocarbon oxidation lies in ‘hybrid’ approaches such as stabilising active metal centres in protective matrices (zeolites, polymers) while using physical stimuli (ultrasound) to overcome diffusion limitations. This unique perspective highlights the transition from purely chemical catalyst design to integrated process intensification, offering a roadmap for energy-efficient and environmentally friendly industrial technologies.

ChemEngineering doi: 10.3390/chemengineering10020024

Authors: Hernán Islas J. Eliecer Méndez Francisco Patiño Sayra Ordoñez Iván A. Reyes Paola B. Bocardo Martín Reyes Miriam Estrada Mizraim U. Flores

Thallium is one of the most toxic elements on the planet, and one alternative method for its precipitation is through jarosite-type compounds. Therefore, in this work, the kinetics of thallium jarosite were evaluated in an alkaline medium (NaOH and Ca(OH)2). Experiments were conducted to assess the effect of medium concentration from 0.03 M to 5.5 × 10−4 M and the effect of temperature from 20 °C to 60 °C. The sigmoidal curves showed an induction period, during which there was no release of sulfur or thallium ions into the solution, nor the formation of solid byproducts, according to the X ray diffraction (XRD) results. Similarly, a progressive conversion period was observed, evidenced by the release of sulfur and thallium ions into the solution and the formation of amorphous solids. Finally, a stability zone is reached, indicating that the decomposition reaction has ended, as there are no changes in the concentration of sulfur and thallium ions in the solution. The reaction was monitored by determining S using Inductively Coupled Plasma (ICP). The experimental results for the progressive conversion period show a better fit to the chemically controlled shrinking core kinetic model. The reaction order for the kinetics in NaOH medium is 1.09 for the induction period and 0.89 for the progressive conversion period, while for Ca(OH)2 medium it is 0.78 for the induction period and 0.47 for the progressive conversion period. The activation energies for the progressive conversion period in the two proposed media are 91.87 kJ mol−1 in NaOH and 71.14 kJ mol−1 in Ca(OH)2, indicating that the controlling mechanism in both systems is the chemical reaction. For the induction period, the activation energies are 101.52 kJ mol−1 and 79.45 kJ mol−1, respectively, indicating that the chemical reaction also controls the initiation of the reactions. The high activation energy in both reaction media suggests that high concentrations of OH− and high temperatures are required to initiate the decomposition reaction. Thallium jarosite precipitates a large amount of thallium and requires high energy to decompose, so it could be a viable alternative in thallium retention.

ChemEngineering doi: 10.3390/chemengineering10020023

Authors: Tamás Kloknicer Gergő Bálint Sárfi Dániel Benjámin Sándor Anita Szabó

Traditional carriers play a major role in wastewater treatment worldwide due to their reliability, ease of production, well-established analytical methods, and strong treatment performance. Recent studies indicate that polyvinyl-alcohol-based microcarriers may surpass conventional media, as their smaller size, higher porosity, and increased specific surface area enable them to retain substantially more biomass within reactors. However, their practical application remains limited because fewer analytical methods and studies exist for these materials, largely due to their small dimensions and heat sensitivity, and their behaviour under industrial conditions—including their kinetics—has yet to be fully characterised and validated. This study aims to address these gaps by reviewing existing biomass measurement standards and highlighting their limitations when applied to microcarriers and by proposing alternative experimental approaches better suited for evaluating biomass on such sensitive yet high-capacity carriers. We present a set of experimental methods (still subject to further refinement) that demonstrate reliable performance with these materials, and to validate our approach, we quantified biomass in both in vitro systems and containerised-scale technologies, reaching up to 14 kg/m3 during winter and 8.7 kg/m3 in spring. Laboratory-scale experiments showed that both heterotrophic and autotrophic cultures can achieve high biomass levels of up to 21 kg/m3 and 16 kg/m3, respectively. Heterotrophs exhibited lower growth inhibition under shear stress, while autotrophs displayed a distinct shear-force niche around 0.09 µN within the reactor.

ChemEngineering doi: 10.3390/chemengineering10020022

Authors: Tomislav Penović Vesna Tomašić Aleksandra Sander Stanislav Kurajica Zoran Gomzi

The conversion of alkanes/alkenes into useful intermediates is highly important in the chemical industry. In this study, the physicochemical properties and catalytically active forms of bismuth molybdates (BiMo) were investigated using the selective oxidation of propene to acrolein as a model reaction. The catalysts were prepared by two methods, coprecipitation and spray-drying, with emphasis on spray-drying. The catalysts were characterized using X-ray diffraction, N2 adsorption/desorption isotherms, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic properties of the BiMo samples were studied in a conventional fixed-bed reactor operated under different reaction conditions. The one-dimensional (1D) pseudohomogeneous model was applied to describe the obtained experimental results. The experimental kinetic data were correlated with two complex kinetic models based on multiple reactions (parallel and serial reaction systems). The proposed models were verified by comparing computer simulation data with experimental laboratory results. This study aimed to extend the understanding of the relationship between catalyst composition/structure and catalyst activity/selectivity for different BiMo structures, and to propose kinetic models using two approaches based on parallel and series reactions, in line with efforts to improve the valorization of light olefins.

ChemEngineering doi: 10.3390/chemengineering10020021

Authors: Jacolien Sussens Jemitias Chivavava Alison E. Lewis

Antisolvent crystallization is a promising method for recovering rare earth elements (REEs). While it offers high theoretical yields of Y2(SO4)3·nH2O from aqueous leach solutions, the recovery is constrained by kinetic limitations. This study examined the crystallization of Y2(SO4)3·nH2O in a fluidized bed reactor (FBR) using ethanol, focusing on the effects of the organic-to-aqueous (O/A) ratio and flow rates on yield and crystal properties. O/A ratios of 0.9 and 1.1 were investigated with an initial Y3+ concentration of 0.87 g/L and a crystallization time of 3 h. The system exhibits multiple rate-limiting steps. At low O/A ratios (0.9), extended induction times indicate either nucleation rate-limitations despite high supersaturation or the possible formation of an initial metastable phase, requiring extended crystallization time for near-equilibrium yields. At high O/A (1.1), elevated supersaturation accelerates nucleation and achieves ~82% yield in 3 h; however, crystal growth exhibited a remaining rate limitation. Lower supersaturation and slower mixing at O/A = 0.9 favored growth, producing crystals with D50 > 34 µm. This work explores how operational parameters influence crystallization behavior while achieving practical yields and acceptable crystal characteristics within a reasonable timeframe. The FBR provided controlled operation, enabling consistent product formation and process flexibility.

ChemEngineering doi: 10.3390/chemengineering10020020

Authors: Andri Kapuji Kaharian Theo Adiwinata Riezqa Andika Abdul Wahid

Maintaining stable pressure in the oxidation–compressor section of purified terephthalic acid (PTA) plants is essential for ensuring efficient and reliable operation. Conventional single-loop proportional integral derivative (PID) controllers frequently perform inadequately because of the large pressure drop between the compressor discharge and reactor inlet, which should ideally remain at approximately 1.2 kg/cm2 above the reactor pressure setpoint but can reach up to 2.8 kg/cm2 due to downstream vapor-phase disturbances. Through this study, we aimed to address this issue by developing a robust cascade pressure control strategy to improve pressure stability and reduce energy losses. Dynamic process models were constructed using system identification techniques to represent real plant behavior, and the best-performing models—identified based on minimum root mean square error (RMSE)—were determined using the Wade method for pressure indicating controller PIC-101, the Lilja method for PIC-102, and the Smith method for pressure differential indicating controller PDIC-101. The proposed cascade configuration was tuned using the Lopez ISE method and evaluated under representative disturbance scenarios. The results showed that the cascade controller significantly improved pressure control, enhanced disturbance rejection, and lowered the risk of reactor shutdowns compared with the conventional proportional-integral PI-based approach. Overall, this study demonstrated that model-driven cascade control can enhance robustness, operational reliability, and energy efficiency in large-scale PTA oxidation processes.

ChemEngineering doi: 10.3390/chemengineering10020019

Authors: María Gómez María Claudia Montiel Elisa Gómez Asunción María Hidalgo Fuensanta Máximo María Dolores Murcia

Growing environmental concern over plastic pollution has increased the need to address the persistence of PET-derived monomers, such as bis(2-hydroxyethyl) terephthalate (BHET) and terephthalic acid (TPA). This work examines the use of excimer radiation lamps combined with hydrogen peroxide (H2O2) to enhance advanced oxidation processes (AOPs) for their degradation. This approach stands out for its high selectivity, absence of mercury, and lower production of toxic byproducts. Experimental tests assessed how different operational factors affect pollutant degradation, such as the initial pollutant concentration (50–200 mg/L), the reaction volume (125–500 mL), and the H2O2:monomer mass ratio (0:1–6:1 for BHET and 0:1–4:1 for TPA). For BHET, the best results occurred with a 5:1 mass ratio, while TPA degraded optimally with a 3:1 ratio, with a 250 mL reaction volume and a 100 mg/L initial concentration for both compounds. Under these conditions, total degradation of the initial monomers was achieved in around 30 and 80 min for BHET and TPA, respectively, and at the end of the reaction, COD decreased by 46% and 32% relative to their initial values. In both cases, hydrogen peroxide was crucial since UV radiation alone led to much lower degradation efficiency. These results emphasize the need to optimize operational conditions for greater efficiency and establish a starting point for future use of excimer technology in the treatment of wastewater contaminated with PET and its derivatives. Additionally, the degradation data closely matched a pseudo-first-order kinetic model (R2 ≈ 1), confirming its reliability for predictive analysis, which is of high importance for the simulation and optimization of the process.

ChemEngineering doi: 10.3390/chemengineering10020018

Authors: Sanghoon Lee Changgook Lee Hyunhee Jeong Sejun Kim Eok Kyun Lee Alan J. Buglass

Brief treatment of a bottled young dry red wine with low-intensity natural emissions in the mid-infrared and far-infrared/near-microwave regions of the electromagnetic spectrum resulted in moderate changes in the concentrations of certain odorants in the wine headspace (vapor), as shown by headspace–solid-phase microextraction–gas chromatography/mass spectrometry (HS-SPME-GC/MS). The headspace levels of certain long-chain ethyl carboxylate esters and methyl salicylate were somewhat enhanced, whereas those of certain aromatic monohydric alcohols, a succinate ester, and oak lactone were somewhat depleted. A tentative explanation of these results is offered whereby waveform treatment results in general re-organization of non-covalent associations of both odorant (volatile) and non-volatile components in wine, leading to the preferential extra release of certain odorants into the headspace (vapor phase) and preferential increased trapping of certain other odorants in wine (liquid phase).

ChemEngineering doi: 10.3390/chemengineering10020017

Authors: Lena Kögel Achim Gieseking Carina Zierberg Mathias Ulbricht Heyko Jürgen Schultz

Mixing processes in stirred tanks are widely applied across various industries, but still offer significant potential for optimization. A promising strategy is the use of double-stage impeller setups instead of conventional single impellers. While multi-impeller configurations are common in tall vessels, their benefits for standard tanks with a height-to-diameter ratio of 1 are largely unexplored. This study systematically investigates the flow fields of single, identical, and mixed double-stage configurations of a Rushton turbine, a pitched-blade turbine, and a retreat curve impeller. To ensure balanced power input in mixed configurations, a refined method for harmonizing specific power via impeller diameter adjustment is proposed. Stereo particle image velocimetry is applied to visualize flow fields, supported by refractive-index matching to enable measurements in a dished-bottom tank. The results reveal substantial flow deficiencies in single-impeller setups. In contrast, double-impeller setups generate novel and significantly improved velocity fields that offer clear advantages and demonstrate strong potential to enhance process efficiency across various mixing applications. These findings provide new experimental insights into the characteristics of dual impellers and form a valuable basis for the design and scale-up of stirred tanks, contributing to more efficient, reliable, and sustainable mixing processes.

ChemEngineering doi: 10.3390/chemengineering10010016

Authors: Svetlana Zhizhkun Lauma Laipniece Igors Astrausks

Soapstock (SS), a by-product of vegetable oil refining, is a promising source of a mixture of mono-, di-, triglycerides, and free fatty acids (MDTG-FFA), a valuable feedstock for biodiesel production. In this study, the selective extraction of MDTG-FFA from SS using green solvents (ethyl acetate, ethyl formate, methyl acetate, isopropyl acetate, and isobutanol) was investigated. Ethyl acetate showed the highest efficiency, allowing the elimination of the phosphatide (PL) precipitation step with acetone. The process optimization was carried out by response surface methodology with central composite design. Statistical analysis confirmed the significance of the obtained models: F-values were 4.55 (p = 0.013) for MDTG-FFA and 9.62 (p = 0.00074) for PL. Regression analysis revealed a good fit of the experimental data with quadratic models for MDTG-FFA and PL, with coefficients of determination (R2) of 0.804 and 0.897, respectively. The optimum extraction parameters were a solvent-to-dry-matter-of-SS ratio 5:1, time 10.2 min, and initial extraction temperature 21.7 °C. Under these conditions, maximum MDTG-FFA yields of 12.6% and 13.4% were achieved for the two batches of SS, respectively, with minimum PL yields of 0.02% and 0.1%. The obtained MDTG-FFA extracts rich in free fatty acids represent a promising feedstock for biodiesel production. The proposed method provides a rational, resource-efficient, and environmentally preferable extraction of valuable components from SS.

ChemEngineering doi: 10.3390/chemengineering10010015

Authors: Veronika Yu. Kolotygina Arkadiy Yu. Zhilyakov Maria A. Bukharinova Ekaterina I. Khamzina Natalia Yu. Stozhko

Green technologies are actively being used to produce nanosized zinc oxide, which is in demand for water purification processes to remove pollutants. Despite the success of the green synthesis of ZnO nanoparticles, no scientific approach exists for selecting plant extracts to produce nanoparticles with the desired properties. This study shows that the antioxidant activity of the plant extracts used is a key parameter influencing the properties of the resulting ZnO nanoparticles. This conclusion is based on the results of nanoparticle synthesis with the use of various plant extracts. The antioxidant activity of the extracts increases in the following order: plum–gooseberry–black currant–strawberry–sea buckthorn. The synthesized ZnO nanoparticles were characterized by UV–visible spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic properties of ZnO nanoparticles were tested under the degradation of a synthetic methylene blue dye after exposure to UV light. We found that with an increase in the AOA of plant extracts, the size of the nanoparticles decreases, while their photocatalytic activity increases. The smallest (d = 13 nm), most uniform in size (polydispersity index 0.1), and most catalytically active ZnO nanoparticles with a small band gap (2.85 eV) were obtained using the sea buckthorn extract with the highest AOA, pH 10 of the reaction mixture and 0.1 M Zn(CH3COO)2∙2H2O as a precursor salt. ZnO nanoparticles synthesized in the sea buckthorn extract demonstrated the highest dye photodegradation efficiency (96.4%) compared with other nanoparticles. The established patterns demonstrate the “antioxidant activity–size–catalytic activity” triad can be considered as a practical guide for obtaining ZnO nanoparticles of a given size and with given properties for environmental remediation applications.

ChemEngineering doi: 10.3390/chemengineering10010014

Authors: Ancuţa Balla Cristina Marcu Maria Mihet Irina Kacsó Septimiu Tripon Alexandru Turza József-Zsolt Szücs-Balázs

Spent coffee grounds (SCG) are an abundant, carbon-rich residue that can be valorized through thermochemical conversion into biochar. Conventional CO2 activation is typically performed in a two-step process, which is time- and energy-consuming. This study aims to evaluate whether a one-step CO2-assisted pyrolysis can produce biochar with comparable or enhanced structural and textural properties while simplifying the process. We compare a two-step pyrolysis process followed by CO2 activation with a one-step CO2-assisted route for producing biochar from SCG. CO2 treatment markedly increases surface area (from 9.8 m2∙g−1 to 550.6–671.0 m2∙g−1) and pore volume. FTIR and Boehm titration indicate depletion of oxygenated surface groups, while N2 adsorption–desorption analyses and SEM reveal a more uniform micro/mesoporous texture for the one-step sample. Although fixed carbon decreases due to gasification, the one-step route delivers superior textural properties in a single thermal stage, reducing energy demand. These results highlight one-step CO2-assisted pyrolysis as an efficient, scalable option for producing high-porosity biochar from coffee waste.

ChemEngineering doi: 10.3390/chemengineering10010013

Authors: Sergey Ivanovich Ponikarov Artem Sergeevich Ponikarov

Modern processes to produce rare-earth elements, strategic metals, and nuclear fuel reprocessing require highly efficient liquid–liquid extraction in systems characterized by high viscosity, elevated interfacial tension, and small density differences. Traditional gravity-driven extractors exhibit low performance under these conditions, whereas centrifugal extractors enable rapid mass transfer and nearly complete phase separation. Differential-contact annular centrifugal contactors offer the highest flexibility and efficiency, but their optimization is limited by the lack of experimental data on the hydrodynamics of liquid flow through perforated nozzles in a rotating field. This limitation hinders the development of accurate computational fluid dynamics (CFD) models (e.g., ANSYS Fluent), reliable equipment scale-up, and the design of optimized contactor configurations. The present study addresses this gap by experimentally determining the flow velocity of liquids through nozzles of various geometries across a wide range of centrifugal accelerations. From these data, a universal power-law correlation was derived, linking the flow rate to rotor speed, nozzle geometry, and the physicochemical properties of the phases. The proposed correlation provides a robust experimental basis for numerical model validation, computational design, and optimization of next-generation differential-contact centrifugal extractors.

ChemEngineering doi: 10.3390/chemengineering10010012

Authors: Jordan Heiki Santos Uemura João Renato de Jesus Junqueira Ângela Christina Conte Theodoro Jefferson Luiz Gomes Corrêa Thaisa Carvalho Volpe Balbinoti Juliana Rodrigues do Carmo

Brazil is one of the richest countries in biodiversity, with biomes that host countless native species of ecological and economic relevance. Among its native fruits, mangaba (Hancornia speciosa) stands out for its nutritional relevance. However, its industrial use remains limited by seasonality, perishability, and harvesting difficulties. This study evaluated the effects of different drying techniques—convective (CD), microwave (MWD), and infrared (IRD)—on the physical and chemical properties of mangaba pulp microcapsules obtained by ionic gelation, including drying kinetics. Drying time varied markedly among treatments, ranging from 25 (MWD) to 185 (IRD) min. In general, the Page modified model provided the best fit for drying kinetics. Physical analyses revealed that IRD produced microcapsules with higher wettability (43.33 s), lower hygroscopicity (203.01 g/100 g), and higher bulk (0.382 g/cm3) and particle density (1.339 g/cm3). CD resulted in greater dispersibility (248.45%) and porosity (0.732), whereas MWD showed the lowest water absorption index (1.78). Regarding bioactive compounds, IRD retained the highest ascorbic acid content, CD preserved more antioxidant activity, and MWD presented the highest total phenolic content. Overall, despite the different processes, mangaba microcapsules retained relevant levels of bioactive compounds, confirming the potential of ionic gelation combined with drying as an effective preservation strategy.

ChemEngineering doi: 10.3390/chemengineering10010011

Authors: Yerkanat N. Kanafin Assylzhan Mukhametrakhimova Rauza Turpanova Stavros G. Poulopoulos

The sustainable management of sewage sludge remains a key environmental challenge for rapidly urbanizing regions such as Kazakhstan. This study explores the potential of sewage sludge-derived biochar as an efficient, low-cost adsorbent for removing Rhodamine B (RhB) dye and toxic metals from water. Sewage sludge was pyrolyzed at 700 °C (BC) and subsequently activated with hydrochloric acid (BCH) and sodium hydroxide (BCN) to improve its surface functionality and porosity. The morphology, surface area, porosity, and functional groups of the obtained biochars were characterized using SEM-EDS, BET, FTIR, and XRD analyses. Batch adsorption experiments demonstrated that the pseudo-second-order kinetic model (R2 = 0.99) best described the data, indicating chemisorption-controlled uptake. Experimental RhB adsorption capacity was 14.53 mg/g for BCH at RhB concentration of 75 mg/L after 120 min. Moreover, BCH exhibited enhanced metal adsorption capacities of 22.85 mg/g (Cu2+), 17.55 mg/g (Zn2+), 15.08 mg/g (Cd2+), 7.97 mg/g (Cr3+), and 3.68 mg/g (As3+). These results confirm that acid activation significantly improves adsorption efficiency compared with pristine biochar due to increased surface area and the introduction of oxygen-containing functional groups. Overall, sewage sludge-derived biochar shows strong potential as a sustainable adsorbent for dye and heavy metal removal.

ChemEngineering doi: 10.3390/chemengineering10010010

Authors: Fatima Pamela Lara-Castillo Jorge Carlos Ríos-Hurtado Sergio Enrique Flores-Villaseñor Alejandro Pérez-Alvarado Rumualdo Servin-Castañeda Gloria I. Dávila-Pulido Adrián A. González-Ibarra

Although carbon filters (CF) can exhibit limited adsorption/selectivity for certain emerging pollutants and operating conditions, incorporating carbon–metal-oxide composites provides a platform to study how surface chemistry, charge distribution and oxide dispersion influence adsorption behavior. This study investigates the incorporation of metal oxides (Fe3O4, TiO2 and CaO) into a commercial carbon filter via mechanical milling, focusing on fundamental changes in surface properties and methylene blue (MB) adsorption mechanisms. The synthesized oxides were characterized by X-ray diffraction and scanning electron microscopy, confirming crystalline structures with crystalline sizes between 11 and 23 nm. Composite filters with varying oxide contents (10–30 wt%) were evaluated for point of zero charge (PZC), surface charge distribution and methylene blue (MB) adsorption. The kinetic experiments were adjusted to pseudo-second order (PSO). Although the maximum adsorption capacity (2.75 mg·g−1 for CaO-modified filters) is lower than commercially activated carbons, this work clarifies how oxide type and dispersion control adsorption performance and interaction mechanisms. Langmuir and Freundlich models revealed monolayer adsorption with favorable dye-surface interactions. These models provide key insights into the role of oxide type and pH in the dye removal process.

ChemEngineering doi: 10.3390/chemengineering10010009

Authors: Marcos Antônio Avibar Ruzza Raquel Laina Barbosa dos Santos Nikolas Ramos Bernardes Carlos Toshiyuki Hiranobe Dener da Silva Souza Michael Jones da Silva Erivaldo Antônio da Silva Renivaldo José dos Santos Leandro Ferreira-Pinto

This study compares the extraction of oils and bioactive compounds from Acmella oleracea using supercritical CO2, pressurized R-134a, and propane under systematically designed experimental conditions. Extraction yields ranged from 1.16–3.35% for CO2, 1.90–2.35% for R-134a, and 1.30–5.42% for propane. Propane achieved the highest yields and the fastest plateau (~35 min), producing extracts dominated by unsaturated fatty acids (linoleic acid ≈ 85%). Supercritical CO2 generated the most diverse chemical profile, combining alkamides (spilanthol), triterpenoids (β-amyrone), and lipids, with a plateau at approximately 50 min, whereas R-134a selectively enriched β-amyrin acetate (~70%) with intermediate kinetics (~45 min). These yield values are typical for non-oilseed species, in which the low natural abundance of the target metabolites renders solvent selectivity more relevant than the total extract mass. Statistical modeling (R2 > 0.96) confirmed that pressure was the main driver of CO2 and propane extraction, whereas temperature dominated R-134a performance. The distinct selectivity patterns revealed by Gas chromatography–mass spectrometry (GC-MS) indicate that each solvent generates compositionally different extracts aligned with specific industrial applications in cosmetics, pharmaceuticals, and nutraceuticals. The unified comparison of these three fluids under a consistent experimental design provides practical insights for rational solvent selection: propane favors unsaturated lipids, CO2 preserves multifunctional compositions, and R-134a targets triterpenoid esters, supporting the economic feasibility of producing enriched, solvent-free plant extracts.

ChemEngineering doi: 10.3390/chemengineering10010008

Authors: Francesca Coccia Lucia Tonucci Andrea Mascitti Rosa Sinisi Carmela Leonessa Michele Ciulla Antonella Fontana Stefano Di Giacomo Nicola d’Alessandro

The coexistence of plastics and metal-based materials in aquatic systems introduces complex interfacial processes that influence pollutant speciation and mobility. This study investigates the role of polystyrene (PS) in promoting UV-induced dissolution of ZnO and Cu2O in aqueous media, revealing a plastic-mediated pathway for metal ion mobilization. Post-use expanded PS fragments were co-dispersed with the oxides and irradiated at 254 nm for 24 h. Ion concentrations were quantified by ICP-MS, while PS morphology and chemistry were characterized by SEM, EDX, FTIR, Raman, and DSC. The presence of PS markedly enhanced metal release, bringing Zn2+ from 29.9 to 50.6 ppm and Cu2+ from 1.1 to 26.5 ppm under irradiation, compared to minimal dissolution in the dark. Spectroscopic analyses indicated negligible polymer degradation, suggesting that enhanced dissolution arises from interfacial photooxidation and associated redox/pH microgradients at the polymer–oxide boundary. These findings demonstrate that PS may serve as a catalytic interface that accelerates UV-driven dissolution of otherwise poorly soluble metal oxides. This mechanism expands current understanding of plastic–pollutant interactions and has implications for predicting metal bioavailability and designing strategies to mitigate pollutant release in sunlit marine and coastal environments.

ChemEngineering doi: 10.3390/chemengineering10010007

Authors: Sharif H. Zein Chukwuchetam A. Akakuru Khalaf J. Jabbar Usama Ahmed A. A. Jalil

Crude distillation units operate as the most energy-intensive refinery operations and generate substantial carbon dioxide emissions. This research models the crude distillation system through its three main components: the atmospheric distillation unit, the naphtha stabilisation unit, and the vacuum distillation unit. The simulation platform Aspen HYSYS version 14.1 enabled optimisation of the preflash drum under product quality constraints, and the analysis included pinch analysis techniques and techno-economic evaluation. The optimisation results demonstrated an 8.95% reduction in atmospheric furnace duty, a 7.38% decrease in total hot utility consumption with the crude distillation system, and an increase in heat recovery capability from 35.57% to 42.71%. Although the preflash process alone decreases profitability because of increased steam demand, combining preflash operation with heat recovery measures maintains both energy conservation and favourable economic performance. The study shows that refinery optimisation requires treating the crude distillation system as a fully integrated process. This approach offers effective strategies to improve energy performance and reduce carbon dioxide emissions while sustaining economic viability. The work differs from previous studies by evaluating the entire distillation system as an integrated sequence and demonstrating how preflash optimisation affects overall energy demand, heat-recovery potential, and economic outcomes while maintaining product quality.

ChemEngineering doi: 10.3390/chemengineering10010006

Authors: Mohamad A. S. Ebrahim Sagheer A. Onaizi Muhammad S. Vohra

The elimination of toxic and long-lasting dyes like crystal violet (CV) from wastewater continues to be a major environmental challenge. Considering this, in this study, a novel amine-modified adsorbent was synthesized by functionalizing ZIF-67 with phosphorylethanolamine (PEA@ZIF-67) nanocomposite to enhance dye removal efficiency. Comprehensive characterization of PEA@ZIF-67 nanocomposite using FTIR, XRD, TGA, and BET techniques confirmed the successful incorporation of PEA into ZIF-67 without compromising the structural integrity of the ZIF-67. The BET specific surface area of PEA@ZIF-67 nanocomposite was noted to be 145.3 m2/g. Furthermore, the application of PEA@ZIF-67 nanocomposite for CV adsorption was investigated and optimized using the Response Surface Methodology (RSM) technique, with the adsorbent dosage, initial dye concentration, and temperature as the operational variables. Under optimized conditions, qmax was 4348 mg/g. Adsorption kinetic studies showed the Avrami model to best fit the respective CV adsorption results, suggesting a heterogeneous and time-dependent mechanism. On the other hand, the Redlich–Peterson adsorption isotherm, which signifies a hybrid adsorption behavior, was noted to be effective. The thermodynamic studies confirmed that the CV adsorption onto PEA@ZIF-67 is spontaneous, endothermic, and entropy-driven. The post-adsorption FTIR and XRD analyses indicated that the used PEA@ZIF-67 was stable, thus supporting its reuse capability.

ChemEngineering doi: 10.3390/chemengineering10010005

Authors: Sharif H. Zein Azeez Ajayi Khalaf J. Jabbar Muhammad Faiq Abdullah Usama Ahmed A. A. Jalil

Refinery blending is a routine operation, yet small changes in crude mix can strongly affect product yield and fuel quality. In this work, Aspen HYSYS v12.1 was used to model and optimize the blending of four Nigerian crude oils—Antan, Usan, Bonga, and Forcados—processed at about 150,000 barrels per day. The study examined how adjustments in blend ratio and feed temperature influence gasoline output and energy use in the distillation unit. The best result was obtained at a blend of Antan 10%, Usan 37.45%, Bonga 10%, and Forcados 42.55%, where gasoline yield increased by roughly 5.6% compared with the equal-blend case. Product properties remained within Nigerian fuel standards (RON ≈ 92, sulphur ≈ 0.038 wt%), showing that quality was not affected by the optimizations. Economic estimates also indicated higher annual revenue and a modest reduction in furnace heat duty, suggesting lower fuel consumption. Although the work was limited to steady-state simulation without plant-scale validation, it provides practical evidence that systematic crude blend optimizations can deliver measurable gains in yield and energy efficiency for refineries using mixed feedstocks.

ChemEngineering doi: 10.3390/chemengineering10010004

Authors: Jaesung Lee

We present a theoretical and numerical framework for computing asymmetric two-dimensional droplet shapes on surfaces with a sharp wetting boundary separating regions of distinct contact angles. Through Lagrange multiplier analysis of the constrained Gibbs free energy functional, we derive a simplified spreading condition that relates the contact line position ratio to the ratio of spreading functions encoding unbalanced Young stress at each contact line, reducing to an explicit algebraic relation that eliminates iterative computation. Gravitational effects substantially modify droplet height and curvature distribution across Bond number regimes, yet the contact line position ratio remains invariant, confirming that horizontal partitioning depends exclusively on interfacial energy ratios rather than body forces. Hydrophilic surfaces exhibit intuitive spreading toward regions with better wettability, producing flattened asymmetric profiles, while hydrophobic surfaces display counterintuitive behavior where droplets preferentially occupy regions with poorer wettability, maintaining tall compact geometries. Mixed hydrophilic–hydrophobic boundaries violate equilibrium conditions and drive spontaneous droplet migration. We develop an efficient two-stage computational strategy decoupling shape computation from equilibrium position determination, reducing computational cost by orders of magnitude. These findings provide quantitative design criteria for controlled droplet positioning on patterned substrates, with implications for microfluidic devices and droplet-based technologies.

ChemEngineering doi: 10.3390/chemengineering10010003

Authors: Manabu Kiguchi Nobuhiro Hanada

Photocatalytic degradation of organic molecules using TiO2 has attracted attention in wastewater treatment because it can decompose organic compounds that are difficult to decompose by other methods. Meanwhile, efficient photocatalytic water treatment is difficult because it is not easy to separate nano-sized photocatalysts from water. In this review, we have described two approaches to solve the water separation challenge in the suspension type TiO2 photocatalysts, which are uniformly distributed in water: magnetic TiO2/SiO2/Fe3O4 nanoparticles and TiO2-polystyrene beads. The preparation, characterization, and photocatalytic performance of the two types of photocatalysts and their application are discussed. Finally, we compare two types of photocatalysts while focusing on the respective advantages and disadvantages of each, and the future direction of research.

ChemEngineering doi: 10.3390/chemengineering10010002

Authors: Diana Barros José Ignacio Alonso-Esteban Tiane C. Finimundy Carla Pereira Josiana A. Vaz Ricardo Pereira-Pinto Élia Fernandes Preciosa Pires Joana Santos Lillian Barros Manuela Vaz-Velho

This study conducted a comprehensive comparison of two green extraction methods, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE), for recovering bioactive phenolic compounds from Pinus pinaster bark. The goal was to valorize timber industry waste and enhance the value of by-products through the development of eco-friendly processes to extract phenolic compounds from Pinus pinaster Aiton subsp. atlantica in northwest Portugal. MAE achieved significantly higher extraction yields than UAE (11.13 vs. 3.47 g extract/100 g bark) and superior total phenolic content (833 vs. 514 mg GAE/g). MAE extracts also exhibited enhanced antioxidant activity in most assays tested (DPPH, ABTS, ORAC, and OxHLIA), while both extracts effectively inhibited lipid peroxidation (TBARS) and showed activity against Gram-positive bacteria. Phenolic profile analysis revealed that MAE recovered a substantially higher amount of total phenolic compounds (230.0 mg/g) compared to UAE (86.95 mg/g), with procyanidins identified as the predominant compounds. The greater recovery of this complex procyanidin mixture by MAE is strongly associated with the enhanced bioactivities observed. Overall, this study confirms MAE as a highly efficient and sustainable technology for transforming pine bark waste into valuable antioxidant and antimicrobial extracts with potential applications in the food and pharmaceutical industries.

ChemEngineering doi: 10.3390/chemengineering10010001

Authors: Bukola Mepaiyeda Michal Ezeh Olaosebikan Olafadehan Awwal Oladipupo Opeyemi Adebayo Etinosa Osaro

The dual imperative of mitigating carbon emissions and maximizing hydrocarbon recovery has amplified global interest in carbon capture, utilization, and storage (CCUS) technologies. These integrated processes hold significant promise for achieving net-zero targets while extending the productive life of mature oil reservoirs. However, their effectiveness hinges on a nuanced understanding of the complex interactions between geological formations, reservoir characteristics, and injection strategies. In this study, a comprehensive machine learning-based framework is presented for estimating CO2 storage capacity and enhanced oil recovery (EOR) performance simultaneously in subsurface reservoirs. The methodology combines simulation-driven uncertainty quantification with supervised machine learning to develop predictive surrogate models. Simulation results were used to generate a diverse dataset of reservoir and operational parameters, which served as inputs for training and testing three machine learning models: Random Forest, Extreme Gradient Boosting (XGBoost), and Artificial Neural Networks (ANN). The models were trained to predict three key performance indicators (KPIs): cumulative oil production (bbl), oil recovery factor (%), and CO2 sequestration volume (SCF). All three models exhibited exceptional predictive accuracy, achieving coefficients of determination (R2) greater than 0.999 across both training and testing datasets for all KPIs. Specifically, the Random Forest and XGBoost models consistently outperformed the ANN model in terms of generalization, particularly for CO2 sequestration volume predictions. These results underscore the robustness and reliability of machine learning models for evaluating and forecasting the performance of CO2-EOR and sequestration strategies. To enhance model interpretability and support decision-making, SHapley Additive exPlanations (SHAP) analysis was applied. SHAP, grounded in cooperative game theory, offers a model-agnostic approach to feature attribution by assigning an importance value to each input parameter for a given prediction. The SHAP results provided transparent and quantifiable insights into how geological and operational features such as porosity, injection rate, water production rate, pressure, etc., affect key output metrics. Overall, this study demonstrates that integrating machine learning with domain-specific simulation data offers a scalable approach for optimizing CCUS operations. The insights derived from the predictive models and SHAP analysis can inform strategic planning, reduce operational uncertainty, and support more sustainable oilfield development practices.

ChemEngineering doi: 10.3390/chemengineering9060146

Authors: Rodrigo Torres-Sciancalepore Daniela Zalazar-García Rosa Rodriguez Gastón Fouga Germán Mazza

This study examines the fast pyrolysis of rosehip seed waste (RSW) in a fluidized bed reactor, evaluating its potential for syngas production and effective waste valorization. The fluidization behavior of sand/RSW mixtures was characterized by determining the minimum fluidization velocity (Umf) from pressure drop measurements. Umf increased with RSW content, ranging from 0.227 to 0.257 m/s. Fluid-dynamic tests conducted in an acrylic prototype assessed bed expansion and mixing, showing stable fluidization at 10% RSW concentration without axial slugging. The bed expanded to 68% above the fixed-bed height, while bubble formation promoted uniform mixing and prevented solid segregation. Pyrolysis experiments were performed in a steel reactor using a nitrogen flow three times the Umf, an initial bed height of 2.5 cm, and a 10% RSW mixture. The reactor operated between 400 and 600 °C, and syngas composition was analyzed. At 600 °C, carbon monoxide and hydrogen yields reached 13.868 mmol/gRSW and 7.914 mmol/gRSW, respectively—values notably higher than those obtained under slow pyrolysis conditions. These findings demonstrate that high-efficiency fluidized bed technology provides a sustainable pathway to convert invasive biomass into clean syngas, integrating waste mitigation with renewable energy generation.

ChemEngineering doi: 10.3390/chemengineering9060145

Authors: Annie Lau Diew Feng Nor Erniza Mohammad Rozali

The energy–water–carbon (EWC) nexus has become a critical concern for industrial systems seeking sustainable development, yet existing assessment approaches often require intensive computation and lack practical adaptability. This study proposes a probability-pinch analysis (P-PA) framework that enhances conventional pinch analysis (PA) by integrating allocation-based correction factors to account for system inefficiencies across all time intervals explicitly. The framework incorporates PA tools, specifically the Power Cascade Table (PCT), Water Cascade Table (WCT), and Energy Planning Pinch Diagram (EPPD), to design ideal energy–water systems that do not consider losses. Correction factors based on probable energy and water flows are then incorporated to capture system inefficiencies, with design modifications proposed to meet annual carbon reduction targets. Results from an industrial plant case study validate the effectiveness of P-PA in establishing minimum resource targets while achieving a 46% reduction in carbon emissions through system modifications. Deviations from conventional PA were within 10%, confirming the framework’s accuracy and reliability in designing integrated energy–water systems within the EWC nexus. It could serve as a handy tool for designing large-scale energy–water systems that require substantial computational effort, but it may be less accurate for small-scale applications. Nevertheless, compared with conventional PA-based approaches, P-PA offers a balanced combination of rigor, simplicity, and adaptability, making it well-suited for industrial EWC nexus analysis and decision support in sustainable process design.

ChemEngineering doi: 10.3390/chemengineering9060144

Authors: Masroor Abro Imran Nazir Unar Junaid Korai Abdul Qudoos Sikandar Almani Abdul Qadeer Laghari Liang Yu Abdul Sattar Jatoi

Computational fluid dynamics (CFD) was used to investigate influence of different gas sparger configurations and the presence of horizontal baffles on hydrodynamic characteristics in a flat bubble column. CFD results of time-averaged local and global gas holdup, liquid axial velocity, and Sauter mean diameter were experimentally validated. Subsequently, the validated CFD model was extended to investigate the effects of different gas sparger configurations, i.e., S1, S3, S4, S5, S8, and S72, and baffles arrangements, i.e., Config-A and Config-B on overall hydrodynamics at different superficial gas velocities (Ug = 0.0014 m/s and 0.0073 m/s). CFD results demonstrated significant influence of both sparger and Ug. Gas holdup and interfacial area increased with smaller, more numerous sparger openings, such that S72 achieved ~1.55 times higher holdup and ~2 higher interfacial area than that of S1. Spargers with fewer and larger openings induced stronger turbulence, which intensified early breakup and coalescence and broadened the bubble size distribution. Results revealed that spargers with many small openings (S72) produced the narrowest distribution, retaining a high fraction of bubbles of initial size (5 mm), whereas spargers with fewer larger openings (S1) generated broader distributions with significant coalescence, especially at higher Ug. The inclusion of baffles enhanced liquid circulation and gas–liquid mixing and contact. However, intensified turbulence below each baffle significantly increased coalescence, producing larger bubbles and resulting in only marginal changes in interfacial area despite increased gas holdup.

ChemEngineering doi: 10.3390/chemengineering9060143

Authors: Mudhar A. Al-Obaidi Farhan Lafta Rashid Ahmed K. Ali Mohammed Mahdi Ahmad Al Astal Iqbal M. Mujtaba

Sodium-ion batteries (SIBs) have arisen as a potential alternative to lithium-ion batteries (LIBs) as a result of the abundant availability of sodium resources at low production costs, making them in line with the United Nations Sustainable Development Goals (SDGs) for affordable and clean energy (Goal 7). The current review intends to comprehensively analyse the various modification techniques deployed to improve the performance of cathode materials for SIBs, including element doping, surface coating, and morphological control. These techniques have demonstrated prominent improvements in electrochemical properties, such as specific capacity, cycling stability, and overall efficiency. The findings indicate that element doping can optimise electronic and ionic conductivity, while surface coatings can enhance stability in addition to mitigating side reactions throughout cycling. Furthermore, morphological control is an intricate technique to facilitate efficient ion diffusion and boost the use of active materials. Statistically, the Cr-doped NaV1−xCrxPO4F achieves a reversible capacity of 83.3 mAh/g with a charge–discharge performance of 90.3%. The sodium iron–nickel hexacyanoferrate presents a discharge capacity of 106 mAh/g and a Coulombic efficiency of 97%, with 96% capacity retention over 100 cycles. Furthermore, the zero-strain cathode Na4Fe7(PO4)6 maintains about 100% capacity retention after 1000 cycles, with only a 0.24% change in unit-cell volume throughout sodiation/desodiation. Notwithstanding these merits, this review ascertains the importance of ongoing research to resolve the associated challenges and unlock the full potential of SIB technology, paving the way for sustainable and efficient energy storage solutions that would aid the conversion into greener energy systems.

ChemEngineering doi: 10.3390/chemengineering9060142

Authors: Sedigheh Ghanbari Daryaee Azizollah Khormali Akram Taleghani Majid Mokaber-Esfahani

Corrosion of carbon steel in acidic media remains a critical challenge during acidizing operations. This study evaluates carrot and rosemary extracts—individually and in combination—as green corrosion inhibitors for carbon steel in 1 M HCl. Inhibition performance was assessed using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), SEM/EDS, and adsorption isotherms. Weight-loss measurements showed inhibition efficiencies of 59.5% (carrot) and 85.7% (rosemary) at 800 ppm, while their 30/70 mixture achieved a markedly higher efficiency of 99.6%. PDP results confirmed this trend, with corrosion current density decreasing from 892 μA/cm2 (blank) to 13.4 μA/cm2 for the mixture, corresponding to 98.5% efficiency. In addition, EIS analysis revealed a substantial increase in charge-transfer resistance from 41.1 ohm·cm2 (blank) to 174.9 ohm·cm2 (carrot), 266.9 ohm·cm2 (rosemary), and 1868.1 ohm·cm2 for the 30/70 mixture, confirming superior barrier formation. Moreover, temperature-dependent tests showed only a 5% efficiency loss for the mixture and an average 6% decrease for the single extracts between 25–45 °C, indicating good thermal stability. Also, SEM images demonstrated severe surface damage in the blank sample, while carrot-, rosemary-, and mixture-treated surfaces showed progressively smoother morphologies. EDS analysis confirmed this trend, with Fe content increasing from 65.78% (blank) to 90.16% (carrot), 91.88% (rosemary), and 94.59% for the mixture. Furthermore, FTIR and GC–MS identified oxygenated functional groups and major phytochemicals responsible for adsorption. Adsorption data followed the Langmuir model, and Gibbs free energy values from −25 to −31 KJ/mol indicated spontaneous mixed physisorption–chemisorption. Overall, the 30/70 carrot–rosemary mixture consistently achieved the highest corrosion protection across all tests, confirming strong synergistic adsorption and demonstrating its potential as a high-performance, eco-friendly inhibitor for acidic environments.

ChemEngineering doi: 10.3390/chemengineering9060141

Authors: Houria Bouziane Soumia Seddari Nadji Moulai-Mostefa

This study investigates the formulation and optimization of acid-stable water-in-oil-in-water (W/O/W) double emulsions stabilized by sodium caseinate (NaCN)–xanthan gum (XG) complexes, with the aim of developing a natural biopolymer-based delivery system exhibiting controlled release behavior. The emulsions were prepared at pH 4, and the effects of NaCN concentration, XG concentration, and primary fraction (PF) on the encapsulation efficiency (EE) and droplet size (DS) were systematically evaluated using response surface methodology (RSM) based on a Box–Behnken design (BBD). Microscopic and rheological analyses confirmed the formation of a rigid interfacial film around the droplets, leading to improved emulsion stability over one month of storage at 4, 25, and 40 °C. The release kinetics of chlortetracycline (CTC), used as a model drug, followed a Fickian diffusion mechanism, indicating efficient control of the release rate by the NaCN/XG interfacial complex. The optimized formulation (NaCN = 0.652%, XG = 0.339%, PF = 10%) yielded an encapsulation efficiency of 87.7% and a mean droplet size of 24.83 µm, demonstrating excellent predictive accuracy of the statistical model. The results highlight the potential of NaCN/XG complexes to produce acid-stable, biopolymer-based double emulsions capable of sustained release of bioactive compounds, making this system promising for food and pharmaceutical delivery applications.

ChemEngineering doi: 10.3390/chemengineering9060140

Authors: Sergio Luis Parra-Angarita Guillermo H. Gaviria Juan F. Herrera-Ruiz María del Carmen Márquez

Monte Carlo methods offer a fast, cost-effective approach for modeling environmental systems influenced by random variability. This study applied them to three abiotic cases: (I) water quality in a lentic surface water source, (II) sizing of a homogenization chamber for solid waste treatment, and (III) removal of atmospheric particulate matter by rain. Deterministic models produced wide and inconsistent estimates: BOD5 concentrations from 5.28 to 19.81 mg/L (275% relative difference), chamber volumes from 24.12 to 116.53 m3, and particulate matter reductions with up to 60 µg/m3 per month variation. Monte Carlo simulations, by contrast, captured system variability and provided more robust outputs: a design value of 94.84 m3 for the homogenization chamber, narrower ranges for BOD5, and realistic distributions of atmospheric PM concentrations. Results show that reliance on average values introduces strong biases and mathematical incompatibilities, while the Monte Carlo approach yields quantitative predictions that are both accurate and operationally useful. This confirms its relevance as a practical tool for analyzing and designing environmental systems under uncertainty.

ChemEngineering doi: 10.3390/chemengineering9060139

Authors: Damião de Carvalho Pereira Drielli Viana Souza Ayres Fernando Rodrigues Gisele Amaral-Labat Patrícia Almeida-Mattos Guilherme Frederico Bernardo Lenz e Silva Flavia Lega Braghiroli Ana Paula Ligeiro de Oliveira José Antônio Silva Júnior Stella Regina Zamuner Vanessa Fierro Alain Celzard Rodrigo Labat Marcos

Having high porosity and biocompatibility, carbon-based materials are promising candidates for tissue engineering applications, particularly as substitutes for biological tissues. This study investigates the growth and viability of osteoblasts on four different activated carbon (AC) materials and correlates biological responses with their physicochemical and morphological properties. Two materials derived from non-renewable sources—AC1, a laboratory-synthesized carbon derived from anthracite, and AC3, a commercial activated carbon (Norit GCN 830) derived from coal—and two commercial activated carbons derived from renewable sources—peat, AC2 (Norit PK1-3), and wood, AC4 (ROX 0.8)—are studied. Results showed that AC1 exhibited the highest porosity (3072 m2/g), with higher phenolic and oxygen-containing surface groups but lower cell viability. In contrast, AC2, AC3, and AC4 displayed lower porosity compared to AC1 (755, 1040, and 1083 m2/g, respectively) and fewer surface phenolic groups but sustained osteoblast proliferation. Notably, AC4 demonstrated superior performance, characterized by regions of fibrous surface, pores in the meso- and microscale range (<50 nm), and enhanced cell viability and proliferation. AC2 also showed favorable results, ranking second for cell growth support. These findings suggest that biomass-derived ACs, particularly AC4 and AC2, provide favorable environments for osteoblast viability and proliferation. AC costs were estimated at 15 to 38 times lower than those for hydroxyapatite and bioceramics, which are widely used for bone cell growth. Thus, ACs made from renewable sources are promising candidates for tissue engineering applications, offering sustainable and effective alternatives for biomedical use.

ChemEngineering doi: 10.3390/chemengineering9060138

Authors: Naveed Ahmed Andrea Straub

This study aims to estimate the organic load of oily wastewater by using Chemical Oxygen Demand (COD) measurements, addressing the analytical challenges posed by the hydrophobic, nonpolar, and often emulsified nature of Fats, oil and grease (FOG). This study established a reproducible and practical methodology for measuring COD in wastewater containing FOG at a laboratory scale, utilizing the nonionic surfactant T80 as a solubilizing and emulsifying agent. Precise gravimetric methods were employed to measure the mass of T80 (indirectly from volume (100–1400 µL/L)) added, and its correlation with COD was established. A strong linear relationship (R2 = 0.993–0.998) between T80 concentration and COD confirmed its stability and suitability as a calibration standard. Experiments with sunflower (1–4 mL/L) and rapeseed oils (1–3 mL/L) showed that COD increased linearly with oil concentration and stabilized after prolonged mixing (96–120 h), indicating complete emulsification and micellar equilibrium. Even under T80 overdose conditions, COD retained linearity (R2 > 0.99), though absolute values were elevated due to excess surfactant oxidation. Temperature variation (5 and 20 °C) and mild heating of coconut fat (30–32 °C) showed no significant effect on COD reproducibility, indicating that mixing time and surfactant dosage are the dominant factors influencing measurement accuracy. Overall, the study establishes T80 as a reliable surfactant for solubilizing oily matrices, providing a consistent and repeatable approach for COD assessment of wastewater containing FOG. The proposed method offers a practical basis and a step towards environmental monitoring and process control in decentralized and industrial wastewater treatment systems.

ChemEngineering doi: 10.3390/chemengineering9060137

Authors: David Oluwasegun Afolayan Hassan Abubakar Adamu Seun Isaiah Olajuyi Olumide Samuel Oluwaseun Ogunmodimu

Mining is associated with specific heavy metals (HMs), including cadmium (Cd), lead (Pb), copper (Cu), iron (Fe), and other toxic metals. These metals contaminate water and accumulate in both children and adults at varying concentrations, resulting in severe health implications. This paper examines the impact of barite mining on water quality, human well-being, and the environment. It evaluates the health implications of natural and anthropogenic activities on the selective liberation of heavy metals at mining sites. The potential environmental impact on mining communities in the extreme dry (April), early or mid-rainy (July), and optimum rainy (October) seasons of the year is also elucidated. Ponds within six barite mining sites were analysed using an Atomic Absorption Spectrometer (AAS) to identify these metals in water samples. The implications of HM concentrations on the well-being of the young and adults were examined and assessed using relevant mathematical expressions, and the outcome was compared with national and international environmental standards. Results show that the ponds within the barite mining sites are contaminated with copper (Cu), barium (Ba), cadmium (Cd), lead (Pb), and iron (Fe). The HM concentration exceeds the reference dose (RfD) or tolerable daily intake (TDI) stated by global and national standards for water quality and healthy living. Statistical assessments indicated that the non-carcinogenic risks of Pb and Cd are higher in children than in adults. In addition to mining, farming activities may increase HM contamination within the areas. It is anticipated that existing policy frameworks and water laws will be reviewed to support efforts for the early detection of HMs in water through medical examinations, water quality assessments, and non-carcinogenic risk (NCR) assessments.

ChemEngineering doi: 10.3390/chemengineering9060136

Authors: Jinfang Zhang Shujun Chen Cheng Lv Shanshan Liu Xinggang Shan Hailong Chen Chen Liu Yujing Bian Jiangfei Lou

To develop a novel pH-responsive multifunctional wound dressing, this study designed a ferulic acid (FA)–cellulose-grafted polymer that leverages the pH-responsive properties of FA. This polymer enables the rapid detection of pH fluctuations in wound environments and effectively monitors acute inflammatory changes. This study innovatively employed FA as the functional compound, horseradish peroxidase (HRP)/ascorbic acid (AA) as the catalytic system, and hydrogen peroxide as the initiator, successfully achieving a grafting reaction between cellulose and FA. Through optimized experiments, the optimal amounts of the FA, AA, HRP enzyme, and hydrogen peroxide were determined. Under these optimal conditions, the K/S value of the FA-grafted fabrics exceeded one, with a grafting rate surpassing 1%. The structure of the cellulose–FA was characterized by FT-IR, HPLC, and 1H NMR, and the possible grafting mechanisms were analyzed. Subsequently, FA-grafted fabric samples were immersed in solutions with varying pH levels, and the material’s pH responsiveness was analyzed through color changes. When the solution’s pH shifted from 3 to 12, the grafted fabric exhibited significant color variations. Consequently, FA-grafted cellulose shows great potential for monitoring skin wound acidity/alkalinity changes and detecting inflammatory responses.

ChemEngineering doi: 10.3390/chemengineering9060135

Authors: Silvia Escudero-Curiel Xacobe M. López-Rodríguez Aida M. Díez Marta Pazos Ángeles Sanromán

This study investigates the valorization of two agri-food residues, specifically olive pomace (alperujo, A) and banana peel (B), into efficient N-doped carbon-based catalysts for polluted wastewater treatment. The residues were converted into hydrochar (HA and HB), which were subsequently N-doped using polyethylenimine (PEI) in combination with cross-linkers (glutaraldehyde (GTA) or 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)) to optimize their catalytic properties. The enhanced hydrochars were utilized as catalysts for the removal of organic pollutants from water by activation of peroxymonosulfate (PMS). Characterization techniques, including CHNS, FTIR, XPS, SEM and electrochemical analysis, were employed to understand the physicochemical properties of the materials. The catalytic activity was evaluated using Reactive Black 5 (RB5) as a model pollutant, with the N-doped alperujo-derived hydrochar cross-linked with EDC (N-HA-EDC) showing the best performance, achieving 80% removal in 60 min and an adsorption capacity of 97 mg/g. The versatility of this functionalization approach was assessed through tests with three pharmaceuticals, corroborating the adaptability and efficacy of the catalyst and demonstrating its potential for wastewater treatment applications. This study provides insights into the development of sustainable, cost-effective carbocatalysts, aligning with circular economy and zero waste principles.

ChemEngineering doi: 10.3390/chemengineering9060134

Authors: Preston C. Wilson Md. Sanaul Huda Roque Evangelista Clairmont L. Clementson Sean Liu Bingcan Chen Ewumbua Monono

Hemp (Cannabis sativa) seed oil is recognized as a valuable oil due to its beneficial fatty acid profile, which includes a favorable balance of omega-6 and omega-3 fatty acids, making it highly desirable for edible and bioproduct applications. Crude hempseed oil contains high concentrations of chlorophyll, carotenoids, and other amphiphilic compounds that can negatively affect its appearance, stability, and downstream processing. Therefore, bleaching is a crucial step in removing these pigments after the degumming and neutralization processes. To optimize the bleaching process, a Box–Behnken response surface methodology was employed, focusing on three factors: time (15, 30, 45 min), temperature (100, 120, 140 °C), and bleaching earth concentration (2.5, 5, and 7.5% w/w). The key response variables were β-carotene, chlorophyll content, and antioxidant activity. For chlorophyll removal, bleaching earth concentration accounted for 83.82% and 81.84% of the variation in the solvent-extracted and mechanically extracted oils, respectively. For β-carotene, the bleaching earth concentration accounted for over 93% of the variation in both types of oil. The optimal bleaching earth concentrations were determined to be 4.87% and 5.36% for the solvent-extracted and mechanically extracted oils, respectively, to achieve the target chlorophyll level of ≤150 ppb. Mechanically extracted oil had lower antioxidant activity after bleaching compared to solvent-extracted oil. The addition of bleaching earth, up to 5%, removed polar antioxidants, further lowering the oil’s antioxidant capacity. These findings suggest that optimizing bleaching conditions can significantly affect both pigment removal and the antioxidant profile of the final product.

ChemEngineering doi: 10.3390/chemengineering9060133

Authors: Balzhan Kabylbekova Nadezhda Vysotskaya Abibulla Anarbaev Roza Spabekova Karim Kurbanbekov Gulnur Kaldybekova Zhakhongir Khussanov

An effective approach to maintaining uninterrupted coolant flow in heat supply systems—and thereby reducing energy consumption—is to prevent the formation of corrosion-scale deposits on the inner surfaces of metal pipes. This is typically achieved by performing anti-corrosion treatment on the coolant. However, the efficiency of this method depends on several factors, including pipe conditions, water flow rate, and water composition. To inhibit corrosion and scale formation on the internal surfaces of pipelines, specific inhibitors are used to create protective films on the metal surface. For strong adhesion of these films, preliminary chemical cleaning of the metal surface with low-concentration acid solutions is essential. This cleaning is usually performed in circulation mode for several hours. The activated surface enhances inhibitor adhesion, leading to the formation of films with improved protective properties. The quality of the anticorrosive films was evaluated using a JSM-6490LV scanning electron microscope equipped with INCAEnergy energy-dispersive microanalysis systems, HKL-Basic structural analysis, ContrAA-300 atomic adsorption spectrometer, and potentiostat IPC-Pro MF.

ChemEngineering doi: 10.3390/chemengineering9060132

Authors: Mojtaba Ghadamgahi Abolfazl Babakhani Hossein Shalchian Ghasem Barati Darband Hamid Reza Shiri

This study presents a comprehensive investigation of copper extraction from chalcopyrite concentrate using choline chloride–malonic acid (ChCl:Ma) deep eutectic solvent (DES) through an integrated experimental and modeling approach. The work began with determination of the deep eutectic temperature (38 °C) for the ChCl:Ma system, which guided the selection of the optimal 1:1 molar ratio to ensure minimal viscosity and maximum solvent stability. The operating temperature range (50–80 °C) was strategically chosen based on TGA analysis confirming the solvent’s thermal stability below 120 °C, ensuring no solvent degradation during leaching experiments. Response Surface Methodology (RSM) with Central Composite Design (CCD) optimization revealed temperature and leaching time (24–72 h) as statistically significant parameters affecting copper recovery, with a highly predictive quadratic model (R2 = 0.99, p < 0.0001). Kinetic analysis using the shrinking core model identified a diffusion-controlled mechanism through a sulfur layer, supported by low activation energies (Cu = 29.09 kJ/mol, Fe = 38.16 kJ/mol). Comprehensive characterization showed preferential chalcopyrite dissolution with direct conversion to elemental sulfur (XRD), formation of metalchlorocomplexes (UV-Vis), and excellent solvent thermal properties (TGA). These findings demonstrate ChCl:Ma DES as an effective medium for chalcopyrite processing, with a systematic methodology providing insights for sustainable non-aqueous metal recovery systems.

ChemEngineering doi: 10.3390/chemengineering9060131

Authors: Michał Sobieraj Dariusz Ksionek Michał Kamiński Filip Karczmarczyk

The application range of a two-phase loop thermosyphon (TPLT) includes electronics cooling and heating and ventilation (HVAC) systems. Combining data center heat removal with HVAC systems can be beneficial in terms of reducing energy use and greenhouse gas emissions. The thermal resistance of the TPLT is the most important parameter affecting its heat transfer ability. This study presents the first experimental characteristics of the TPLT, working with novel low Global Warming Potential (GWP) fluids, including the evaporating and condensing performance. The operation of the TPLT is evaluated with pure fluids R600a, R32, and their mixture R600a/R32 at heat sink temperature in the range of 25 °C to 35 °C under heat input from 50 W to 225 W. The novel mixture presents the highest temperature at the evaporator outlet. Pure fluids R600a and R32 show the highest heat transfer coefficients and the lowest thermal resistance. The flow visualization is performed to study the boiling flow patterns. Empirical correlations are employed to predict the boiling-heat transfer coefficients. Thermal characteristics are obtained for further development of TPLT operating with environmentally friendly fluids.

ChemEngineering doi: 10.3390/chemengineering9060130

Authors: Jelena Tamuliene Jonas Sarlauskas

In this study, we investigated the impact of incorporating energetic substituents such as –NO2, –NH2, –Cl, –F, N-methyl-N-nitro (CH3–N–NO2), and picryl on the detonation performance and stability of acridone-based compounds. The B3LYP/cc-pVTZ approach was applied to investigate the influence of substitutions on the stability and detonation properties of acridone derivatives. The results obtained exhibit the significant influence of both the type and position of substituents on the energetic performance and stability of the compounds studied. Notably, the acridone derivative bearing a picryl group and four –NH2 substituents exhibited energetic properties superior to those of 2,4,6-trinitrotoluene (TNT). Its calculated velocity lies in the range [7.45–7.66] km/s, and its detonation pressure is [22.49–24.36] GPa; however, its stability is lower than that of core compounds. This reduction, however, is dependent on both the nature and number of substituents introduced.

ChemEngineering doi: 10.3390/chemengineering9060129

Authors: Sergei A. Solovev Olga V. Soloveva

A numerical model was developed to simulate a fluidized bed reactor for isobutane dehydrogenation. First, we constructed a hydrodynamic model of catalyst particle fluidization and a kinetic model for three chemical reactions in a simple lab-scale reactor (H = 70 cm, D = 2.8 cm). Experimental studies and numerical simulation of the laboratory reactor were carried out at four temperatures: 550, 575, 600, and 625 °C. The product yield results from the computational fluid dynamics simulation show a close match to the experimental data. The optimal process temperature in the laboratory reactor is 575 °C, at which the isobutylene yield is ~46.03 wt%. With decreasing temperature, the isobutylene yield decreases, and it rises as temperature increases. However, with rising temperature, the total yield of by-products increases on average to 20 wt%. We compared the CFD simulation results for two laboratory reactor models: a 3D model and a 2D axisymmetric model. For gas phase fractions, absolute deviations ranged from 0.01 to 1.12%, while relative deviations were between 0.006% and 0.114%. However, there are differences in the solid-phase particle dynamics. Second, we applied the constructed CFD model to simulate an industrial-scale reactor (H = 23.81 m, D = 4.6 m). In addition to its size, the industrial reactor differs from the laboratory reactor in its heating principle. In this configuration, the gas, preheated to 550 °C, and the catalyst particles, at 650 °C, are fed into the entire volume. The objective of this study is to test the performance of the model, which was verified on a laboratory reactor, for simulating an industrial reactor. Temperature fields and zones of reaction product formation are analyzed. The average isobutylene yield is ~31.88 wt%, which is consistent with the operation of real reactors but lower than the results for the laboratory reactor at all temperatures. The industrial reactor is more challenging to heat uniformly. It contains many internal elements that affect the movement of the gas–solid system. Overall, the model developed for the laboratory reactor has proven to be suitable for CFD modeling of an industrial reactor.

ChemEngineering doi: 10.3390/chemengineering9060128

Authors: Lukas von Damnitz Denis Anders

Static mixers are widely used devices for efficient fluid mixing, homogenization, and enhancement of heat transfer, with applications ranging from chemical processing and pharmaceutical manufacturing to wastewater treatment. This review provides a structured overview of mixing processes and the key metrics used to assess mixing quality in static mixers. Conceptual models such as dispersive versus distributive mixing and the classification into macro-, meso-, and micromixing are introduced as a basis for understanding mixing phenomena. Subsequently, a comprehensive set of quantitative measures, including G-value, residence time distribution, intensity of segregation, coefficient of variation, striation-based descriptors, Lyapunov exponent, extensional efficiency, and shear rate, is discussed in detail. Correlations and relationships among these measures are highlighted to facilitate their application in characterizing mixing quality in static mixers. By systematically summarizing the theoretical background, definitions, and interconnections of mixing quality measures, this review aims to provide researchers and engineers with a clear framework for evaluating and comparing mixing quality in static mixers, thereby supporting both academic studies and practical design considerations.