Journal Description

ChemEngineering

ChemEngineering is an international, peer-reviewed, open access journal on the science and technology of chemical engineering, published bimonthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
Journal Rank: CiteScore - Q1 (General Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 21.5 days after submission; acceptance to publication is undertaken in 7.8 days (median values for papers published in this journal in the first half of 2023).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 2.5 (2022); 5-Year Impact Factor: 2.7 (2022)

Imprint Information Journal Flyer Open Access ISSN: 2305-7084

Latest Articles

Open AccessArticle

Modeling and Adoption of Technological Solutions in Order to Enhance the Effectiveness of Measures to Limit Water Inflows into Oil Wells under Conditions of Uncertainty

and

ChemEngineering 2023, 7(5), 89; https://doi.org/10.3390/chemengineering7050089 - 19 Sep 2023

Abstract

This article is devoted to the construction and statistical analysis of models that express the relationship between performance indicators and a large number of geological and technological factors. The volume of additionally produced oil, the volume of limited water, the duration of the effect and profit per well, taking into account the cost of the polymer, are taken as performance indicators. The key goal of the article is to develop a method and models for making technological choices to enhance the effectiveness of measures to limit water inflows in production wells under conditions of uncertainty. The methodological basis of the study was the provisions and principles of mathematical statistics, the theory of fuzzy sets, the theory of decision-making under conditions of uncertainty based on materials generated by statistical processing of data on physical and geological conditions, and the results of waterproofing work, obtaining, and analyzing information. The scientific novelty of the study lies in the construction of technological solutions based on modeling the performance indicators of waterproofing works with an assessment of the significance of each factor and the reliability of the models and decision-making under conditions of uncertainty, expressed by multi-criteria and multi-factoriality. The practical significance follows from a solution that satisfies the conditions for achieving the maximum of all indicators of the efficiency of the process of limiting water inflows, both technological and economic. An algorithm was developed and implemented for evaluating optimal technological solutions according to four criteria based on information about the geological and physical conditions of the field and the experience of implementing geological and technical measures to limit water inflows, including the analysis of factors, their weighted contribution, model building, statistical evaluation of reliability indicators, decision-making taking into account uncertainty. Full article

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Open AccessPerspective

Time Crystal Synthon: The Way to Integrate Cascade Reactions for Advancing Multistep Flow Synthesis

Pathik Sahoo

ChemEngineering 2023, 7(5), 88; https://doi.org/10.3390/chemengineering7050088 - 18 Sep 2023

Abstract

Multistep flow catalytic reactions in organic chemistry integrate multiple sequential organic reactions to enhance cost-efficiency, time management, and labour resources, all while boosting effectiveness and environmental sustainability. Similar to how we select molecular synthons for reactions in retrosynthesis, we can employ time-crystal synthons to integrate catalytic reaction cycles in the development of a reaction pathway. This involves considering individual catalytic reaction steps of cycles as time-consuming events that can be topologically arranged like a clock. This results in a perpetual machine that violates time translational symmetry, leading to the production of a time crystal. This approach involves transferring a single product from one catalytic cycle to a neighbouring reaction cycle, connecting various reaction vessels vertically to establish a ‘cascade’ of reaction cycles. Additionally, catalytic cycles can be integrated by sharing common reaction steps or implementing a metathesis reaction at the junction zone of two neighbouring cycles. Here, the concept of time-crystal synthons facilitates the linear integration of heterogeneous catalytic cycles, step by step, to transfer products through the common reaction medium when modifying conventional flow synthesis. Significantly, this time-crystal synthon-driven multistep approach offers advantages over conventional flow synthesis, as the reaction vessels can be equipped with microwave and photosynthesis methodologies, allowing for the collection of specific products from their respective vessels as needed, providing more options to integrate reactions and enabling flow control using gravity. Full article

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Open AccessFeature PaperArticle

Numerical Simulation, Preparation, and Evaluation of Cu(In, Ga)Se₂ (CIGS) Thin-Film Solar Cells

Borhan Albiss

and

Mohammad Al-Widyan

ChemEngineering 2023, 7(5), 87; https://doi.org/10.3390/chemengineering7050087 - 15 Sep 2023

Abstract

This study presents the numerical simulation, optimization, preparation, and characterization of Cu(In, Ga)Se₂ (CIGS) thin-film solar cells (TFSCs). Different cell parameters were investigated, including Ga/(Ga+In) (GGI) ratios, the thicknesses of CIGS absorption layers, the fill factor (FF), the open-circuit voltage (Voc), and the short-circuit current (Isc). The effects of the simulated parameters on the power conversion efficiency (η) of each prototype CIGS cells were investigated. The optimal GGI ratio was approximately 0.6. Using COMSOL Multiphysics software, a CIGS layer thickness of 2 μm and an η of 17% was calculated, assuming constant operating temperatures. Moreover, prototype CIGS solar cells with various compositions were prepared via a simple and cost-effective method based on sol–gel, sonication, and spin-coating techniques. The microstructures and electrical and optical properties of the CIGS-based solar cells were evaluated using current–voltage (I-V) characteristics, scanning electron microscopy (SEM), X-ray diffraction, atomic force microscopy (AFM), and UV-vis spectroscopy. The elemental compositions of the solar cell layers were evaluated via energy-dispersive X-ray fluorescence (EDXRF). The obtained results were compared with the experimental results. For example, in a prototype cell with a CIGS absorption layer thickness of 2 μm and a GGI ratio of 0.6, the experimental value of η was about 15%. Our results revealed that the agreement between the simulation results and the experimental findings for most of the simulated parameters is quite good. These findings indicate that a non-destructive analysis based on EDXRF is a versatile tool for evaluating CIGS solar cells in a very short time with excellent repeatability for both layer composition and thickness. Full article

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Open AccessArticle

Bicarbonate-Activated Hydrogen Peroxide for an Azo Dye Degradation: Experimental Design

Karla Y. Mora-Bonilla

Iván F. Macías-Quiroga

Nancy R. Sanabria-González

and

María T. Dávila-Arias

ChemEngineering 2023, 7(5), 86; https://doi.org/10.3390/chemengineering7050086 - 14 Sep 2023

Abstract

The present study investigated the degradation of an aqueous Allura Red AC (AR–AC) solution by activating hydrogen peroxide with bicarbonate using cobalt ion (Co²⁺) as the catalyst. Four independent variables (H₂O₂, NaHCO₃, Co²⁺, and dye concentrations) were analyzed in the composite central design (CCD). AR–AC degradation was optimized using the response surface methodology (RSM). Under optimal degradation conditions (41.86 mg/L AR–AC, 5.58 mM H₂O₂, 2.00 mM NaHCO₃, and 9.00 µM Co²⁺), decolorization > 99.86%, mineralization (CO₂ to conversion) of 12.99%, and total nitrogen removal of 51.97% were achieved. The predicted values for the three response variables were consistent with the experimental values, with determination coefficients (R²) greater than 0.9053. Because cobalt ions (Co²⁺) are a source of water pollution, after oxidation, these were adsorbed on sodium bentonite (Na–Bent), obtaining a final concentration of <0.01 mg/L. Bicarbonate-activated hydrogen peroxide is a potential technology for dye wastewater treatment that operates at an alkaline pH and at ambient temperature. Full article

(This article belongs to the Topic Advances in Chemistry and Chemical Engineering)

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Open AccessArticle

Enhancing Heat Transfer Performance in Simulated Fischer–Tropsch Fluidized Bed Reactor through Tubes Ends Modifications

and

Muthanna H. Al-Dahhan

ChemEngineering 2023, 7(5), 85; https://doi.org/10.3390/chemengineering7050085 - 14 Sep 2023

Abstract

Fluidized bed reactors are essential in a wide range of industrial applications, encompassing processes such as Fischer–Tropsch synthesis and catalytic cracking. The optimization of performance and reduction in energy consumption in these reactors necessitate the use of efficient heat transfer mechanisms. The present work examines the considerable impact of tube end geometries, superficial gas velocity, and radial position on heat transfer coefficients within fluidized bed reactors. It was found that the tapered tube end configurations have been empirically proven to improve energy efficiency in fluidized bed reactors significantly. For example, at a superficial gas velocity of 0.4 m/s, the tapered end form’s local heat transfer coefficient (LHTC) demonstrated a significant 20% enhancement compared to the flat end shape. The results and findings of this work make a valuable contribution to the advancement of complex models, enhance the efficiency of fluidized bed reactor processes, and encourage further investigation into novel tube geometries. Full article

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Open AccessArticle

Crystallization Behavior of Ceritinib: Characterization and Optimization Strategies

Iva Zokić

and

Jasna Prlić Kardum

ChemEngineering 2023, 7(5), 84; https://doi.org/10.3390/chemengineering7050084 - 14 Sep 2023

Abstract

Because of the specific thermodynamic properties of active pharmaceutical ingredients, the process of crystallization often meets implementation challenges in the pharmaceutical industry. Therefore, it is essential to select the appropriate method and system for the crystallization of a drug. Ceritinib, an active ingredient in the treatment of lung cancer, was formed as a result of pH modification during the cooling crystallization of ceritinib dihydrochloride solution. By carrying out processes in various solvent systems, several polymorphs were produced. A combination of forms B and C was generated in the ethanol–water system, resulting in smaller crystals. The acetone–water system produced pure form A, which has larger crystals and is more applicable for forthcoming studies. To additionally enhance granulometric properties, ceritinib form A was recrystallized in tetrahydrofuran at different temperatures using antisolvent crystallization. Crystallization at a higher saturation temperature results in larger and more compact crystals, which enhances filtration and drying. Full article

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Open AccessArticle

Assessment of Bioactive Compounds in Red Peppercorns (Piper nigrum L.) for the Development of Red Peppercorns Powder

Sovannmony Lay

Sochetra Sen

and

Peany Houng

ChemEngineering 2023, 7(5), 83; https://doi.org/10.3390/chemengineering7050083 - 12 Sep 2023

Abstract

Red pepper powder is used as a spice added to various types of foods to improve the spiciness and aroma of foods. The unique aroma and spiciness of red pepper are related to the contents of bioactive compounds, including alkaloids, phenolic compounds, terpenes, and flavonoids. These phytochemical compounds have extensively provided many biological activities, such as antioxidant, anti-inflammatory, and antimicrobial. The assessment of bioactive compounds in red pepper is crucial to evaluate the quality of red pepper powder. Therefore, the objective of this study aimed to analyze total phenolic and total flavonoid compounds for further red peppercorn powder application. To assess the contents of bioactive compounds, Response Surface Methodology (RSM) with Box–Behnken Design (BBD) was applied to design the experiment and analyze the data. Furthermore, extraction conditions such as extraction time (30 to 150 min), temperature (35 to 65 °C), and solid-to-solvent ratio (0.5:10 to 0.5:20 g/mL) were investigated for their effects on the yield of total phenolic and total flavonoid contents. The result of this study found that all extraction parameters significantly affected the extraction yields of phenolic and flavonoid compounds. The aroma and taste of red pepper powder can be adjusted by changing extraction conditions such as temperature, time, and solid-to-solvent ratio because changing these conditions allowed the bioactive compounds to be extracted from red pepper at different concentrations. Overall, the assessment of bioactive compounds in red peppercorns holds significant importance for their application as red peppercorn powder. Full article

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Open AccessArticle

Chitosan–Resole–Pectin Aerogel in Methylene Blue Removal: Modeling and Optimization Using an Artificial Neuron Network

Jean Flores-Gómez

Mario Villegas-Ruvalcaba

José Blancas-Flores

and

Juan Morales-Rivera

ChemEngineering 2023, 7(5), 82; https://doi.org/10.3390/chemengineering7050082 - 11 Sep 2023

Abstract

In this study, a novel chitosan–resole–pectin aerogel (CS–R–P) was created from a sol–gel reaction with a solution of Cs and P with resole by a freeze-drying technique, and this adsorbent was proposed for the removal of methylene blue (MB). In addition, with the use of an artificial intelligence technique known as an artificial neural network (ANN), this material was modeled and optimized. Its physical morphology and chemical composition were also characterized with FTIR and XPS, and its adsorption properties were analyzed. For modeling the adsorption process, three main parameters were used: the chitosan–resole–pectin concentration (45–75%), thermal treatment (6–36 h), and known concentrations of methylene blue (25–50 and 100 mg/L), established on the Box–Behnken design. The ANN was coupled with the improved gray wolf optimization (IWGO) metaheuristic algorithm, achieving a correlation coefficient of R² = 0.99. The characterization indicates that the surface of the aerogels was micro- and mesoporous, the resole gave physical stability, and the polysaccharide base delivered the functional groups necessary for dye adsorption; the aerogels were successful dye adsorbents with a q_e of 12.44 mg/g. Finally, the physical and chemical sorption was ascertainable with an adsorption that followed pseudo-second-order kinetics. The MB adsorption was clearly occurring though cation exchange and hydrogen binding as observed in the chemical composition. The ANN with the gray wolf optimizer was used for the prediction of the best operating parameters for MB removal, applying the following conditions—the CS–R–P aerogel concentration (52/30/18), the thermal treatment (9.12 h), and the initial concentration of methylene blue (37 mg/L)—achieving a 94.6% removal. These conclusions suggest that using artificial intelligence such as an ANN can provide an efficient and practical model for maximizing the removal action of new aerogels based on chitosan. Full article

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Open AccessArticle

Rheology of Aqueous Ferrofluids: Transition from a Gel-Like Character to a Liquid Character in High Magnetic Fields

Stanislav Čampelj

ChemEngineering 2023, 7(5), 81; https://doi.org/10.3390/chemengineering7050081 - 07 Sep 2023

Abstract

Rheological measurements under an applied magnetic field were used to investigate the changes to the internal structure and stability of an aqueous ferrofluid. The ferrofluid was prepared by dispersing 1.8 wt.% of maghemite nanoparticles with a size of d = 14 ± 3 nm and a saturation magnetization M_S = 68 emu/g in water using citric acid as the surfactant. In this study, oscillatory tests were used to investigate the internal structural changes and the stability of ferrofluid under the influence of the magnetic field B. In a magnetic field of approximately 50 mT, the G′ became higher than the loss modulus G″ as the ferrofluid exhibited a gel-like character. However, at a magnetic field of approximately 200 mT, the character of the ferrofluid reverted to that of a liquid. The change in the character of the ferrofluid in this high magnetic field was associated with a gradual change from chain agglomerates to the energetically more favourable globular agglomerates, using a calculation based on a model described in a separate work. The globular agglomerates impeded the flow to a much lesser degree than the chains, causing a reduction in the viscosity. Further increase of the magnetic field resulted in sedimentation of agglomerates and loss of magneto-rheological effect. Full article

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Open AccessArticle

Modeling the Mechanical Properties of a Polymer-Based Mixed-Matrix Membrane Using Deep Learning Neural Networks

Zaid Abdulhamid Alhulaybi

Muhammad Ali Martuza

and

Sayeed Rushd

ChemEngineering 2023, 7(5), 80; https://doi.org/10.3390/chemengineering7050080 - 04 Sep 2023

Abstract

Polylactic acid (PLA), the second most produced biopolymer, was selected for the fabrication of mixed-matrix membranes (MMMs) via the incorporation of HKUST-1 metal–organic framework (MOF) particles into a PLA matrix with the aim of improving mechanical characteristics. A deep learning neural network (DLNN) model was developed on the TensorFlow 2 backend to predict the mechanical properties, stress, strain, elastic modulus, and toughness of the PLA/HKUST-1 MMMs with different input parameters, such as PLA wt%, HKUST-1 wt%, casting thickness, and immersion time. The model was trained and validated with 1214 interpolated datasets in stratified fivefold cross validation. Dropout and early stopping regularizations were applied to prevent model overfitting in the training phase. The model performed consistently for the unknown interpolated datasets and 26 original experimental datasets, with coefficients of determination (R2) of 0.93–0.97 and 0.78–0.88, respectively. The results suggest that the proposed method can build effective DLNN
models using a small dataset to predict material properties. Full article

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Open AccessArticle

Interconversion and Removal of Inorganic Nitrogen Compounds via UV Irradiation

Alejandro M. Senn

and

Natalia Quici

ChemEngineering 2023, 7(5), 79; https://doi.org/10.3390/chemengineering7050079 - 31 Aug 2023

Abstract

Dissolved inorganic nitrogen (DIN) species are key components of the nitrogen cycle and are the main nitrogen pollutants in groundwater. This study investigated the interconversion and removal of the principal DIN compounds (

{NO}_{3}^{-}

{NO}_{2}^{-}

and [...] Read more.

{NO}_{3}^{-}

{NO}_{2}^{-}

and

{NH}_{4}^{+}

) via UV light irradiation using a medium-pressure mercury lamp. The experiments were carried out systematically at relatively low nitrogen concentrations (1.5 mM) at varying pHs in the presence and absence of oxygen to compare the reaction rates and suggest the reaction mechanisms.

{NO}_{3}^{-}

was fully converted into

{NO}_{2}^{-}

at a pH > 3 in both oxic and anoxic conditions, and the reaction was faster when the pH was increased following a first-order kinetic at pH 11 (k = 0.12 min⁻¹, R² = 0.9995).

{NO}_{2}^{-}

was partially converted into

{NO}_{3}^{-}

only at pH 3 and in the presence of oxygen and was stable at an alkaline pH. This interconversion of

{NO}_{3}^{-}

and

{NO}_{2}^{-}

did not yield nitrogen loss in the solution. The addition of formic acid as an electron donor led to the reduction of

{NO}_{3}^{-}

{NH}_{4}^{+}

. Conversely,

{NH}_{4}^{+}

was converted into

{NO}_{2}^{-}

{NO}_{3}^{-}

and to an unidentified subproduct in the presence of

O_{2}^{}

at pH 10. Finally, it was demonstrated that

{NO}_{2}^{-}

and

{NH}_{4}^{+}

react via UV irradiation with stoichiometry 1:1 at pH 10 with the total loss of nitrogen in the solution. With these results, a strategy to remove DIN compounds via UV irradiation was proposed with the eventual use of solar light. Full article

(This article belongs to the Special Issue Process Intensification for Chemical Engineering and Processing)

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Open AccessArticle

Dynamic and Steady-State Simulation Study for the Stabilization of Natural Gas Condensate and CO₂ Removal through Heating and Pressure Reduction

and

Muhammad Fazal Ul Basit

ChemEngineering 2023, 7(5), 78; https://doi.org/10.3390/chemengineering7050078 - 29 Aug 2023

Abstract

Stabilization of condensate is a highly energy-consuming process compared to other oil and gas processes. There is a need to reduce this energy consumption. Therefore, the present work aims to simulate the stabilization unit in terms of available energy and on-spec stabilized condensate products. Natural gas condensate liquids (NGL) need to be stabilized by eliminating lighter hydrocarbon gases and acid gases before being sent to the refinery. Stabilized NGL has the vapor pressure determined as a Reid vapor pressure of 7 psia, showing that light components did not evolve as a separate gas phase. Stabilization and CO₂ removal was performed through the distillation method by heating and pressure reduction using steady state and dynamic simulation through Aspen HYSYS. Different process alterations around the exchanger and column have been studied based on the utilities available for the stabilization and CO₂ removal process. Sensitivity studies, including the impact of CO₂ concentration, the temperature at the inlet of the stabilizer flash separator, and the dynamic simulation for the PID controller, have been performed to analyze the impact on the process parameters, such as Reid vapor pressure (RVP) and CO₂ of the rundown air cooler and heat duties of the exchangers. Actual plant data have been used for the validation of process simulation values for the accuracy of the condensate stabilization unit model. Based on the scenarios analyzed, it can be concluded that the nitrogen stripping method achieved 7 ppmv CO₂ and 7 psia RVP in the condensate from the cooler outlet, while a variation of 29 bpd was observed for the stabilized condensate flowrate throughout all scenarios with data validation showing 0.24% discrepancy between Aspen Hysys data and actual plant data. Full article

(This article belongs to the Special Issue Green and Environmentally Sustainable Chemical Processes)

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Open AccessReview

Modifying Superparamagnetic Iron Oxide Nanoparticles as Methylene Blue Adsorbents: A Review

Linh Doan

ChemEngineering 2023, 7(5), 77; https://doi.org/10.3390/chemengineering7050077 - 28 Aug 2023

Abstract

Methylene blue (MB) is a hazardous chemical that is widely found in wastewater, and its removal is critical. One of the most common methods to remove MB is adsorption. To enhance the adsorption process, magnetic adsorbents, particularly those based on superparamagnetic iron oxide nanoparticles (SPION), play a vital role. This study focuses on comparing recent novel SPION-based MB adsorbents and how to acquire the critical parameters needed to evaluate the adsorption and desorption mechanisms, including isotherms, kinetics, and thermodynamic properties. Moreover, the review article also discusses the future aspects of these adsorbents. Full article

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Open AccessArticle

Chemical and Process Inherent Safety Analysis of Large-Scale Suspension Poly(Vinyl Chloride) Production

Ángel Darío González-Delgado

Eduardo Aguilar-Vásquez

and

Miguel Ramos-Olmos

ChemEngineering 2023, 7(5), 76; https://doi.org/10.3390/chemengineering7050076 - 24 Aug 2023

Abstract

In this work, a safety assessment was carried out for the suspension polymerization method, known for the lack of studies about its sustainable performance and long history of chemical accidents. Therefore, a safety analysis was conducted using the inherent safety methodology to assess and determine the inherent risks of the poly(vinyl chloride) (PVC) suspension production process using computer-aided process engineering (CAPE). The indicators were calculated using data from safety databases and the specialized literature, considering downstream stages like vinyl chloride monomer (VCM) recovery, PVC purification and PVC drying. The obtained indicators revealed that the process has a negative performance regarding inherent safety, with a total inherent safety index of 30. The chemical inherent safety index had a value of 19, with the main chemical risk of the process being presented by the vinyl chloride monomer (with a value of 11), along with the risk of the exothermic reactions. The process safety index had a value of 15, highlighting the inventory as the primary concern of the process (with a value of 5), followed by the presence of unsafe equipment such as furnaces, burners, and dryers. The safety structure index had a score of 3, categorizing the process as probably risky, with the reaction and purification stages being more susceptible to accidents. Lastly, it is recommended to reduce the size of the process inventory and to substitute out unsafe process units. Full article

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Open AccessArticle

Effects of Phosphate and Thermal Treatments on the Characteristics of Activated Carbon Manufactured from Durian (Durio zibethinus) Peel

Astrilia Damayanti

Ria Wulansarie

Zuhriyan Ash Shiddieqy Bahlawan

Suharta

Mutia Royana

Mikhaella Wai Nostra Mannohara Basuki

Bayu Nugroho

and

Ahmad Lutvi Andri

ChemEngineering 2023, 7(5), 75; https://doi.org/10.3390/chemengineering7050075 - 22 Aug 2023

Abstract

The availability of fossil energy is dwindling, so renewable fuels are the alternative choices, one of which is bioethanol. To increase the purity of the ethanol produced via the fermentation process, activated carbon (AC) was made from durian (Durio zibethinus) peel. The steps for making AC consist of carbonization (300 °C and 400 °C), chemical activation using phosphoric acid (10–40%), pyrolysis (700 °C and 800 °C), and neutralization. The results showed that the maximum surface area (326.72 m²/g) was obtained from 400 °C carbonization, 800 °C pyrolysis, and activation using a 40% phosphoric acid solution. Other characteristics are the surface area of 326.72 m²/g, pore radius of 1.04 nm, and total pore volume of 0.17 cc/g with phosphate residue in the form a P₂O₅ molecule of 3.47% by weight, with COOH, OH, CO, C=C, C=O, P-OC, and Fe-O groups with wavenumbers (cm⁻¹), respectively, of 3836, 3225, 2103, 1555, 1143, and 494. The AC also demonstrated the highest number of carbon (86.41%) upon detection using EDX, while XRF analysis verified an average carbon content of 94.45 wt%. The highest ethanol adsorption efficiency (%) and the lowest yield (%) of AC (%) were 90.01 ± 0.00 and 23.26 ± 0.01. This study shows that durian peel has great potential as the raw material for the activated carbon manufacture of ethanol adsorbents. Full article

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Open AccessArticle

Closed-Loop Stability of a Non-Minimum Phase Quadruple Tank System Using a Nonlinear Model Predictive Controller with EKF

Ismaila A. Oyehan

Ajiboye S. Osunleke

and

Olanrewaju O. Ajani

ChemEngineering 2023, 7(4), 74; https://doi.org/10.3390/chemengineering7040074 - 17 Aug 2023

Abstract

The dynamics of a quadruple tank system (QTS) represent an extensive class of multivariate nonlinear uncertain systems found in the industry. It has been established that changes in split fractions affect the transmission zero location, thereby altering the operating conditions between the minimum and non-minimum phase regions. The latter is difficult to control as more fluid flows into the two upper tanks than into the two bottom tanks, resulting in competing effects between the initial and final system responses. This attribute, alongside nonlinearity, uncertainties, constraints, and a multivariate nature, can degrade closed-loop system performance, leading to instability. In this study, we addressed the aforementioned challenges by designing controllers for the regulation of the water flow in the two bottom tanks of the QTS. For comparative analysis, three controller algorithms—a nonlinear model predictive controller (NMPC), NMPC augmented with an extended Kalman filter (i.e., NMPC-EKF) and linear model predictive controller (LMPC)—were considered in the analysis and design of the control mechanism for the quadruple water level system in a non-minimum phase condition via the Matrix Laboratory (MATLAB) simulation package environment. The simulated and real-time results in the closed loop were analyzed, and the controller performances were considered based on faster setpoint responses, less oscillation, settling time, overshoot, and smaller integral absolute error (IAE) and integral square error (ISE) under various operational conditions. The study showed that the NMPC, when augmented with an EKF, is effective for the control of a QTS in the non-minimum phase and could be designed for more complex, nonlinear, and multivariable dynamics systems, even in the presence of constraints. Full article

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Open AccessArticle

Electrochemical Degradation of Diuron by Anodic Oxidation on a Commercial Ru_0.3Ti_0.7O₂ Anode in a Sulfate Medium

Lucas B. de Faria

Guilhermina F. Teixeira

and

ChemEngineering 2023, 7(4), 73; https://doi.org/10.3390/chemengineering7040073 - 17 Aug 2023

Abstract

This work presents the electrochemical degradation of the herbicide Diuron by anodic oxidation on a Ti/Ru_0.3Ti_0.7O₂ metal mixed oxide anode using sulfate as the electrolyte. The study includes the influence of Diuron concentration and current density on anodic oxidation. The results evidence a first-order degradation, with the highest capacity achieved at 40 mA cm⁻² and at an initial Diuron concentration of 38 mg L⁻¹. Nevertheless, in terms of efficiency and energy demand, the operation at 10 mA cm⁻² is favored due to the more efficient and less energy-consuming condition. To discern the optimum design and operation conditions, this work presents the results of a preliminary technical–economic analysis, demonstrating that, to minimize the total costs of the system, it is recommended to seek the most efficient conditions, i.e., the conditions demanding the lowest applied charges with the highest Diuron degradation. At the same time, attention must be given to the required cell voltage to not increase excessively the operating costs. Full article

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Open AccessArticle

Recovery of Polyphenolic Antioxidants from Coffee Silverskin Using Acid-Catalyzed Ethanol Organosolv Treatment

George Smyrnakis

George Stamoulis

Dimitrios Palaiogiannis

Theodoros Chatzimitakos

Vassilis Athanasiadis

Stavros I. Lalas

and

Dimitris P. Makris

ChemEngineering 2023, 7(4), 72; https://doi.org/10.3390/chemengineering7040072 - 12 Aug 2023

Abstract

The examination presented herein sought to establish a novel methodology for the efficient recovery of polyphenolic antioxidants from coffee processing residues, namely coffee silverskin (CSS). The process developed was an ethanol-based organosolv treatment, assisted by acid catalysis, using sulfuric acid or oxalic acid as the catalyst. The first approach was modeling treatment based on severity, where it was found that treatment dependence on time and temperature may well be described by linear relationships. Response surface methodology was then deployed as a consecutive stage, to optimize treatments with regard to catalyst concentration and resident time. In this case, again, linear models could effectively predict polyphenol recovery yield (Y_TP). For the sulfuric-acid-catalyzed treatment, the maximum theoretic Y_TP was found to be 10.95 ± 0.44 mg caffeic acid equivalent (CAE) g⁻¹ DM, achieved at C_SuAc = 1.5% and t = 300 min. On the other hand, the maximum Y_TP of 10.30 ± 0.53 could be attained at C_OxAc = 4%, and t = 300 min. Considering treatment severity, it was concluded that the use of oxalic acid, a food-grade organic acid, instead of sulfuric acid, a corrosive acid, would afford equivalent effects at lower severity. The high-performance liquid chromatography analyses also revealed that the extract produced through the oxalic-acid-catalyzed treatment was more enriched in neochlorogenic and chlorogenic acids, and it exhibited stronger antiradical activity, but weaker ferric-reducing effects. It is proposed that the methodology developed may contribute towards the use of coffee processing wastes as potential sources of bioactive ingredients and the design of novel functional products, in the frame of a more sustainable strategy for coffee processing companies. Full article

(This article belongs to the Special Issue Thermal Treatment of Biomass and Solid Municipal Waste)

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Graphical abstract

Open AccessArticle

Low-Waste Synthesis and Properties of Highly Dispersed NiO·Al₂O₃ Mixed Oxides Based on the Products of Centrifugal Thermal Activation of Gibbsite

Aleksey V. Zhuzhgov

Lyubov A. Isupova

Evgeny A. Suprun

and

Aleksandr S. Gorkusha

ChemEngineering 2023, 7(4), 71; https://doi.org/10.3390/chemengineering7040071 - 29 Jul 2023

Abstract

This study revealed an increased reactivity of centrifugally thermoactivated products of gibbsite toward aqueous solutions of nickel nitrate at room temperature as well as under hydrothermal conditions. X-ray, thermal, microscopy, adsorption and chemical analysis methods were used to investigate and demonstrate the possibility of obtaining highly loaded mixed aluminum–nickel oxide systems, with a nickel content of ca. 33 wt.%, using a hydrochemical treatment at room temperature or a hydrothermal treatment of suspensions of the product of the centrifugal thermal activation of gibbsite in aqueous solutions of nickel nitrate. It was shown that the thermal treatment of xerogels—hydrochemical interaction products—in the range of 350–850 °C led to the formation of NiO phases and highly dispersed solid solutions of nickel based on the NiAl₂O₄ spinel structure, with different ratios and a high specific surface area of 140–200 m²/g. A hydrochemical treatment of suspensions at room temperature ensures that the predominant formation of the NiO phase is distributed over the surface of the alumina matrix after calcination, whereas hydrothermal treatment at 150 °C leads to a deeper interaction of the suspension components at the treatment step, which occurs after the thermal treatment of the formed xerogel in the predominant formation of poorly crystallized NiAl₂O₄ spinel (“protospinel”). The considered method makes it possible to obtain complex aluminum–nickel oxide systems with different phase ratios, decreases the number of initial reagents and synthesis steps, completely excludes waste and diminishes the total amount of nitrates by 75 wt.% compared to the classical nitrate scheme for the coprecipitation of compounds with a similar elemental composition. Full article

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Open AccessArticle

Recent Progress in the Viscosity Modeling of Concentrated Suspensions of Unimodal Hard Spheres

Rajinder Pal

ChemEngineering 2023, 7(4), 70; https://doi.org/10.3390/chemengineering7040070 - 27 Jul 2023

Abstract

The viscosity models for concentrated suspensions of unimodal hard spheres published in the twenty-first century are reviewed, compared, and evaluated using a large pool of available experimental data. The Pal viscosity model for unimodal suspensions is the best available model in that the predictions of this model agree very well with the low (zero)-shear experimental relative viscosity data for coarse suspensions, nanosuspensions, and coarse suspensions thickened by starch nanoparticles. The average percentage error in model predictions is less than 6.5%. Finally, the viscous behavior of concentrated multimodal suspensions is simulated using the Pal model for unimodal suspensions. Full article

(This article belongs to the Special Issue Exclusive Collection: Papers from the Editorial Board Members (EBMs) of ChemEngineering)

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