Processes

20 pages, 12534 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effects of the PMMA Molecular Weight on the Thermal and Thermo-Oxidative Decomposition as the First Chemical Stage of Flaming Ignition

by Antonio Galgano and Colomba Di Blasi

Processes 2024, 12(1), 219; https://doi.org/10.3390/pr12010219 - 19 Jan 2024

Viewed by 1231

Abstract

The piloted and the spontaneous ignition of low and high molecular weight (LMW and HMW) polymethyl methacrylate are simulated using a one-dimensional condensed-gas phase model for constant heat fluxes in the range of 25–150 kW/m². Purely thermal (nitrogen) and thermo-oxidative (air) [...] Read more.

The piloted and the spontaneous ignition of low and high molecular weight (LMW and HMW) polymethyl methacrylate are simulated using a one-dimensional condensed-gas phase model for constant heat fluxes in the range of 25–150 kW/m². Purely thermal (nitrogen) and thermo-oxidative (air) decomposition is considered, described by a single and four-step kinetics for the low and high molecular weight polymer, respectively. Different optical properties are also examined. The same trends of the ignition time and other ignition parameters are always observed. Due to a more significant role of the chemical kinetics, the effects of the sample molecular weight and reaction atmosphere are higher at low heat fluxes. Times are shorter for the black HMW samples and thermo-oxidative kinetics. For piloted ignition, factors are around 2.8–1.6, whereas for thermal decomposition, they are 1.3–1.2. The corresponding figures are 1.8–1.3 and 1.3–1.1, in the same order, for the spontaneous ignition. Overall, the effects of the molecular weight are more important than those related to the reaction kinetics environment. These differences are confirmed by the comparison between predictions and measurements. Full article

(This article belongs to the Special Issue High-Temperature Behavior of Polymers and Composites)

► Show Figures

Figure 1

16 pages, 1692 KiB

Open AccessEditor’s ChoiceArticle

Ciprofloxacin Uptake from an Aqueous Solution via Adsorption with K₂CO₃-Activated Biochar Derived from Brewing Industry Bagasse

by Víctor Francisco Meseguer, Juan Francisco Ortuño, María Isabel Aguilar, Mercedes Lloréns, Ana Belén Pérez-Marín and Emmanuel Fuentes

Processes 2024, 12(1), 199; https://doi.org/10.3390/pr12010199 - 17 Jan 2024

Cited by 6 | Viewed by 2063

Abstract

Ciprofloxacin (CPX), an antibiotic considered as an emerging contaminant, needs to be removed from aquatic environments. This work investigates the adsorption of CPX on K₂CO₃-activated biochar (AB). The biochar was obtained via the pyrolysis of barley bagasse from the [...] Read more.

Ciprofloxacin (CPX), an antibiotic considered as an emerging contaminant, needs to be removed from aquatic environments. This work investigates the adsorption of CPX on K₂CO₃-activated biochar (AB). The biochar was obtained via the pyrolysis of barley bagasse from the brewing industry, and then it was activated with 2M of K₂CO₃. The activated biochar was characterised using FTIR spectroscopy and a pH_PZC assay. Batch adsorption tests were performed to study the influence of pH and temperature on CPX sorption and to obtain kinetic and equilibrium data. The adsorption of CPX on AB was favoured by increasing the temperature from 10 °C to 55 °C, demonstrating the endothermic nature of the process. The level of CPX removal after 24 h of contact and at pH 3.5 was 82% of that obtained when equilibrium was reached. The kinetic study showed that the adsorption is well described by the Elovich and the Bangham kinetic models. The adsorption is favourable, and the best fits to the experimental equilibrium data were obtained with the Freundlich, Redlich–Peterson and Sips isotherms. In an acidic solution (pH = 3.5) and at 25 °C, the maximum CPX adsorption capacity of AB was ≈105 mg·g⁻¹, comparable to that reported for other adsorbents. Full article

(This article belongs to the Special Issue Municipal Wastewater Treatment and Removal of Micropollutants)

► Show Figures

Figure 1

18 pages, 1980 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Conversion of Pistachio and Walnut Shell Waste into Valuable Components with Subcritical Water

by Maja Čolnik, Mihael Irgolič, Amra Perva and Mojca Škerget

Processes 2024, 12(1), 195; https://doi.org/10.3390/pr12010195 - 16 Jan 2024

Cited by 7 | Viewed by 4523

Abstract

Pistachio and walnut shells accumulate in large quantities as waste during food processing and represent a promising lignocellulosic biomass for the extraction of valuable components. Subcritical water technology was used as an environmentally friendly technique to study the extraction of active ingredients and [...] Read more.

Pistachio and walnut shells accumulate in large quantities as waste during food processing and represent a promising lignocellulosic biomass for the extraction of valuable components. Subcritical water technology was used as an environmentally friendly technique to study the extraction of active ingredients and other valuable degradation products from walnut and pistachio waste. Subcritical water extraction (SWE) was carried out under different process conditions (temperature (150–300 °C) and short reaction times (15–60 min)) and compared with conventional extraction using different organic solvents (acetone, 50% acetone and ethanol). The extracts obtained from pistachio and walnut shell waste are rich in various bioactive and valuable components. The highest contents of total phenols (127.08 mg GA/g extract at 300 °C for 15 min, from walnut shells), total flavonoids (10.18 mg QU/g extract at 200 °C for 60 min, from pistachio shells), total carbohydrates (602.14 mg TCH/g extract at 200 °C for 60 min, from walnut shells) and antioxidant activity (91% at 300 °C, for 60 min, from pistachio shells) were determined when the extracts were obtained via subcritical water. High contents of total phenols (up to 86.17 mg GA/g extract) were also determined in the conventional extracts obtained with ethanol. Using the HPLC method, sugars and their valuable derivatives were determined in the extracts, with glucose, fructose, furfurals (5-hydroxymethylfurfural (5-HMF) and furfural) and levulinic acid being the most abundant in the extracts obtained by subcritical water. The results show that subcritical water technology enables better exploitation of biowaste materials than conventional extraction methods with organic solvents, as it provides a higher yields of bioactive components such as phenolic compounds and thus extracts with high antioxidant activity, while at the same time producing degradation products that are valuable secondary raw materials. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

► Show Figures

Graphical abstract

11 pages, 5801 KiB

Open AccessEditor’s ChoiceArticle

Variability in Physical Properties of Logging and Sawmill Residues for Making Wood Pellets

by Jun Sian Lee, Hamid Rezaei, Omid Gholami Banadkoki, Fahimeh Yazdan Panah and Shahab Sokhansanj

Processes 2024, 12(1), 181; https://doi.org/10.3390/pr12010181 - 13 Jan 2024

Cited by 2 | Viewed by 1467

Abstract

Wood pellets are a versatile ingredient to produce bioenergy and bioproducts. Wood pellet manufacturing in Canada started as a way of using the excess sawdust from sawmilling operations. With the recent dwindling availability of sawdust and the growth in demand for wood pellets, [...] Read more.

Wood pellets are a versatile ingredient to produce bioenergy and bioproducts. Wood pellet manufacturing in Canada started as a way of using the excess sawdust from sawmilling operations. With the recent dwindling availability of sawdust and the growth in demand for wood pellets, the industry uses more non-sawdust woody biomass as feedstock. In this study, woody biomass materials received from nine wood pellet plants in British Columbia (BC) and Alberta were analyzed for their properties, especially those used for fractionating feedstock to make pellets. Half of the feedstock received at the plants was non-sawdust. Moisture contents varied from 10 to 60% wet basis, with the hog having an average of 50%. Ash contents ranged from 0.3 to 4% dry basis and were highest in the hog fraction. Bulk density varied from 50 to 450 kg/m³, with shavings having the lowest bulk density. Particle density ranged from 359 kg/m³ for infeed mix to 513 kg/m³ for sawdust. In total, 25% of particles received were larger than 25 mm. The extraneous materials (sand, dirt) in the infeed materials ranged from 0.03% to 1.2%, except for one hog sample (8.2%). Plant operators use mechanical fractionation and blending to meet the required ash content. In conclusion, further instrumental techniques to aid in fractionation should be developed. Full article

(This article belongs to the Section Chemical Processes and Systems)

► Show Figures

Figure 1

21 pages, 7285 KiB

Open AccessEditor’s ChoiceArticle

A Numerical Simulation Study into the Effect of Longitudinal and Transverse Pitch on Deposition of Zhundong Coal Ash on Tube Bundles

by Zipeng Guo, Jianbo Li, Yintang Liang, Xiaofei Long, Xiaofeng Lu and Dongke Zhang

Processes 2024, 12(1), 178; https://doi.org/10.3390/pr12010178 - 12 Jan 2024

Cited by 1 | Viewed by 1257

Abstract

In this paper, the dynamic deposition behavior of Na-enriching Zhundong coal ash on tube bundles with varying longitudinal and transverse pitches was numerically studied. By using a modified critical viscosity model, an improved CFD deposition model has been established and key parameters, including [...] Read more.

In this paper, the dynamic deposition behavior of Na-enriching Zhundong coal ash on tube bundles with varying longitudinal and transverse pitches was numerically studied. By using a modified critical viscosity model, an improved CFD deposition model has been established and key parameters, including deposit mass and morphology, particle trajectories and impaction and sticking probabilities, as well as the heat flux distribution, have been analyzed. The results show that the ash deposited on tubes in the first row is, respectively, 1.74 and 3.80 times higher than that on the second and third rows, proving that ash deposition in the downstream is lessened. As the longitudinal pitch increased from 1.50 D to 2.50 D, deposit mass in the downstream increased two times, suggesting that an increase in longitudinal pitch would aggravate ash deposition. The effect of transverse pitch, however, with the least deposit propensity at S_t/D = 1.75, is non-linear due to the joint effect of adjacent tubes and walls in affecting particle trajectory. In addition, due to the non-uniform distribution of the deposit, heat flux across the tube is the smallest at the stagnation point but becomes six times higher at two sides and the leeward, which makes the thermal damage of these sides to be warranted as a practical concern. Full article

(This article belongs to the Special Issue Modeling and Optimization of Gas-Solid Reaction Vessels)

► Show Figures

Figure 1

15 pages, 2261 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Microbiome Structure of Activated Sludge after Adaptation to Landfill Leachate Treatment in a Lab-Scale Sequencing Batch Reactor

by Mihaela Kirilova, Ivaylo Yotinov, Yovana Todorova, Nora Dinova, Stilyana Lincheva, Irina Schneider and Yana Topalova

Processes 2024, 12(1), 159; https://doi.org/10.3390/pr12010159 - 9 Jan 2024

Cited by 2 | Viewed by 2220

Abstract

During adaptation to waters that are rich in xenobiotics, biological systems pass through multiple stages. The first one is related to the restructuring of communities, pronounced destruction of the structure, and multiplication of active biodegradants. The purpose of the present research was to [...] Read more.

During adaptation to waters that are rich in xenobiotics, biological systems pass through multiple stages. The first one is related to the restructuring of communities, pronounced destruction of the structure, and multiplication of active biodegradants. The purpose of the present research was to describe the microbiome restructuring that occurs during the adaptation stage in landfill leachate treatment. In a model SBR (sequencing batch reactor), a 21-day purification process of landfill leachate was simulated. Wastewater was fed in increasing concentrations. When undiluted leachate entered, the activated sludge structure disintegrated (Sludge Volume Index—4.6 mL/g). The Chemical Oxygen Demand and ammonium nitrogen concentration remained at high values in the influent (2321.11 mgO₂/L and 573.20 mg/L, respectively). A significant amount of free-swimming cells was found, and the number of aerobic heterotrophs and bacteria of the genera Pseudomonas and Acinetobacter increased by up to 125 times. The Azoarcus-Thauera cluster (27%) and Pseudomonas spp. (16%) were registered as the main bacterial groups in the activated sludge. In the changed structure of the microbial community, Gammaproteobacteria, family Rhizobiaceae, class Saccharimonadia were predominantly represented. Among the suspended bacteria, Microbactericeae and Burkholderiaceae, which are known for their ability to degrade xenobiotics, were present in larger quantities. The enzymological analysis demonstrated that the ortho-pathway of cleavage of aromatic structures was active in the community. The described changes in the leachate-purifying microbial community appear to be destructive at the technological level. At the microbiological level, however, trends of initial adaptation were clearly outlined, which, if continued, could provide a highly efficient biodegradation community. Full article

(This article belongs to the Special Issue Integrated Approaches to Eco-Friendly Processes for Persistent Pollutants Contamination)

► Show Figures

Figure 1

12 pages, 1069 KiB

Open AccessEditor’s ChoiceArticle

Surface Chemistry of Cherry Stone-Derived Activated Carbon Prepared by H₃PO₄ Activation

by Jose M. González-Domínguez, Carmen Fernández-González, María Alexandre-Franco and Vicente Gómez-Serrano

Processes 2024, 12(1), 149; https://doi.org/10.3390/pr12010149 - 8 Jan 2024

Cited by 6 | Viewed by 1564

Abstract

The preparation of activated carbons (ACs) from cherry stones and chemical activation with H₃PO₄ can be controlled by the experimental variables during the impregnation step in order to obtain a tailored porous structure of the as-prepared ACs. This control not [...] Read more.

The preparation of activated carbons (ACs) from cherry stones and chemical activation with H₃PO₄ can be controlled by the experimental variables during the impregnation step in order to obtain a tailored porous structure of the as-prepared ACs. This control not only extends to the ACs’ texture and porosity development, but also to the chemical nature of their surface. The spectroscopic and elemental characterization of different series of ACs is presented in this study. The spectroscopic band features and assignments strongly depend on the H₃PO₄ concentration and/or the semi-carbonization treatments applied to the feedstock before impregnation, which ultimately influence different characteristics such as the AC hydrophilicity. Different surface chemistries arise from the different tailored impregnation solutions, showing a practical outcome for future applications of the as-prepared ACs. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Vicente Gómez Serrano: Innovation in Production, Characterization and Applications of Activated Carbon, Biochar and Other Carbon-Based Materials)

► Show Figures

Figure 1

17 pages, 3682 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Characterizing Novel Acetogens for Production of C2–C6 Alcohols from Syngas

by Rahul Thunuguntla, Hasan K. Atiyeh, Raymond L. Huhnke and Ralph S. Tanner

Processes 2024, 12(1), 142; https://doi.org/10.3390/pr12010142 - 6 Jan 2024

Cited by 3 | Viewed by 1624

Abstract

Utilizing syngas components CO, CO_2, and H₂ to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, [...] Read more.

Utilizing syngas components CO, CO_2, and H₂ to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, and the creation of cost-effective media are crucial. This study compared syngas fermentation capabilities of three novel strains (Clostridium carboxidivorans P20, C. ljungdahlii P14, and C. muellerianum P21) with existing strains (C. ragsdalei P11 and C. carboxidivorans P7) in three medium formulations. Fermentations in 250-mL bottles were conducted at 37 °C using H₂:CO₂:CO (30:30:40) using P11, P7, and corn steep liquor (CSL) media. Results showed that P11 and CSL media facilitated higher cell mass, alcohol titer, and gas conversion compared to the P7 medium. Strains P7, P14, and P20 formed 1.4- to 4-fold more total alcohols in the CSL medium in comparison with the P7 medium. Further, strain P21 produced more butanol (0.9 g/L) and hexanol (0.7 g/L) in the medium with CSL, offering cost advantages over P7 and P11 media containing yeast extract. Enhancing strain activity and selectivity in converting syngas into C4 and C6 alcohols requires further development, medium formulation improvements, and characterization, particularly for the new strain P21. Full article

(This article belongs to the Special Issue Fermentation and Bioprocess Engineering Processes)

► Show Figures

Graphical abstract

19 pages, 3798 KiB

Open AccessEditor’s ChoiceArticle

Prediction and Diagnosis of Electric Vehicle Battery Fault Based on Abnormal Voltage: Using Decision Tree Algorithm Theories and Isolated Forest

by Zhaosheng Zhang, Shiji Dong, Da Li, Peng Liu and Zhenpo Wang

Processes 2024, 12(1), 136; https://doi.org/10.3390/pr12010136 - 5 Jan 2024

Cited by 10 | Viewed by 3349

Abstract

Battery voltage is a pivotal parameter for evaluating battery health and safety. The precise prediction of battery voltage and the implementation of anomaly detection are imperative for ensuring the secure and dependable operation of battery systems. Nevertheless, during the actual operation of electric [...] Read more.

Battery voltage is a pivotal parameter for evaluating battery health and safety. The precise prediction of battery voltage and the implementation of anomaly detection are imperative for ensuring the secure and dependable operation of battery systems. Nevertheless, during the actual operation of electric vehicles, battery performance is subject to the influence of the vehicle's operational state and battery characteristic parameters, introducing challenges to safety alerts. In order to address these challenges and achieve precise battery voltage prediction, this paper comprehensively considers the battery characteristics and driving behavior of electric vehicles in both charging and operational states. Mathematical processing, including averaging and variance calculation, is applied to the battery characteristic parameter data and driving behavior data. By integrating historical voltage data and employing a modified gradient boosting decision tree algorithm (GBDT), a fast and accurate online voltage prediction method is proposed. Hyperparameter optimization is employed to minimize prediction voltage errors. The accuracy and timeliness of the predictions are validated through a comprehensive evaluation and comparison of the forecasted voltages. To diagnose anomalies in battery voltage, the paper proposes a fault diagnosis method that combines the Isolation Forest and Boxplot techniques. Finally, utilizing authentic electric vehicle data for validation, the research underscores the capability of the proposed method to achieve accurate voltage predictions six minutes in advance and provide effective fault diagnosis. This investigation carries substantial practical implications for fortifying battery management and optimizing the performance of electric vehicles. Full article

► Show Figures

Figure 1

20 pages, 7880 KiB

Open AccessEditor’s ChoiceArticle

Investigation of the Mixing Time Distribution and Connected Flow Fields in Two-Stage Stirred Vessels

by Marian Matzke, Mathias Ulbricht and Heyko Jürgen Schultz

Processes 2024, 12(1), 132; https://doi.org/10.3390/pr12010132 - 4 Jan 2024

Cited by 3 | Viewed by 1615

Abstract

In this study, laser-induced fluorescence is used to investigate the homogenization in stirred vessels equipped with single- and two-stage stirrers. The acquired local mixing times across the reactor cross-section are plotted as mixing time distribution (MTD) and then compared with the previously measured [...] Read more.

In this study, laser-induced fluorescence is used to investigate the homogenization in stirred vessels equipped with single- and two-stage stirrers. The acquired local mixing times across the reactor cross-section are plotted as mixing time distribution (MTD) and then compared with the previously measured flow fields of the identical systems. With the help of a novel evaluation method, the mixing times are characterized with a normal distribution fit. With mean value and standard deviation as determined parameters, the mixing results of different installation heights and stirrer combinations are quantitatively evaluated and lead to clear recommendations for installations that enable efficient mixing. Full article

(This article belongs to the Special Issue Simulation and Measurement of Flows in Chemical Process Engineering—Trends, Insights and Applications)

► Show Figures

Figure 1

17 pages, 1752 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An Experimental Investigation of Hydrogen Production through Biomass Electrolysis

by Muhammad Umer, Caterina Brandoni, Mohammad Jaffar, Neil J. Hewitt, Patrick Dunlop, Kai Zhang and Ye Huang

Processes 2024, 12(1), 112; https://doi.org/10.3390/pr12010112 - 2 Jan 2024

Cited by 12 | Viewed by 4538

Abstract

This work investigated hydrogen production from biomass feedstocks (i.e., glucose, starch, lignin and cellulose) using a 100 mL h-type proton exchange membrane electrolysis cell. Biomass electrolysis is a promising process for hydrogen production, although low in technology readiness level, but with a series [...] Read more.

This work investigated hydrogen production from biomass feedstocks (i.e., glucose, starch, lignin and cellulose) using a 100 mL h-type proton exchange membrane electrolysis cell. Biomass electrolysis is a promising process for hydrogen production, although low in technology readiness level, but with a series of recognised advantages: (i) lower-temperature conditions (compared to thermochemical processes), (ii) minimal energy consumption and low-cost post-production, (iii) potential to synthesise high-volume H₂ and (iv) smaller carbon footprint compared to thermochemical processes. A Lewis acid (FeCl₃) was employed as a charge carrier and redox medium to aid in the depolymerisation/oxidation of biomass components. A comprehensive analysis was conducted, measuring the H₂ and CO₂ emission volume and performing electrochemical analysis (i.e., linear sweep voltammetry and chronoamperometry) to better understand the process. For the first time, the influence of temperature on current density and H₂ evolution was studied at temperatures ranging from ambient temperature (i.e., 19 °C) to 80 °C. The highest H₂ volume was 12.1 mL, which was produced by FeCl₃-mediated electrolysis of glucose at ambient temperature, which was up to two times higher than starch, lignin and cellulose at 1.20 V. Of the substrates examined, glucose also showed a maximum power-to-H₂-yield ratio of 30.99 kWh/kg. The results showed that hydrogen can be produced from biomass feedstock at ambient temperature when a Lewis acid (FeCl₃) is employed and with a higher yield rate and a lower electricity consumption compared to water electrolysis. Full article

(This article belongs to the Special Issue Sustainability Use of Wood/Wood Residues and Other Bioenergy Sources)

► Show Figures

Graphical abstract

19 pages, 15096 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Self-Assembly in Curved Space: Ordering, Defect and Entropy

by Yuming Wang, Haixiao Wan, Lijuan Gao, Yibo Wu and Li-Tang Yan

Processes 2024, 12(1), 119; https://doi.org/10.3390/pr12010119 - 2 Jan 2024

Cited by 1 | Viewed by 2691

Abstract

Self-assembly of nanoscale objects is of essential importance in materials science, condensed matter physics, and biophysics. Curvature modifies the principles and sequence of self-assembly in Euclidean space, resulting in unique and more complex structures. Understanding self-assembly behavior in curved space is not only [...] Read more.

Self-assembly of nanoscale objects is of essential importance in materials science, condensed matter physics, and biophysics. Curvature modifies the principles and sequence of self-assembly in Euclidean space, resulting in unique and more complex structures. Understanding self-assembly behavior in curved space is not only instrumental for designing structural building blocks and assembly processes from a bottom-up perspective but is also critically important for delineating various biological systems. In this review, we summarize efforts made to unveil the physical nature of self-assembly in curved space through experiments and simulations. First, we outline the differences in the physical nature of self-assembly between curved space and Euclidean space by presenting relevant results of experiments and simulations. Second, we explore the principles of self-assembly in curved space at multiple scales and interactions, elucidating important factors that govern the self-assembly process from the perspectives of confinement and structural building blocks. Finally, we enumerate practical applications and control strategies for self-assembly in curved space and outline the challenges and prospects in this field. We hope that this review will encourage further efforts toward fundamental research and broaden the potential applications of designed assemblies in curved space. Full article

(This article belongs to the Special Issue Modeling and Simulation in Polymer Reaction Engineering)

► Show Figures

Figure 1

16 pages, 7953 KiB

Open AccessEditor’s ChoiceCommunication

First Approach Using Fluidic Force Microscopy (FluidFM^®) to Measure Adhesion Forces between Droplets and Flat/Rough Surfaces Immersed in Water

by Laura Schwan and Ulrich Bröckel

Processes 2024, 12(1), 99; https://doi.org/10.3390/pr12010099 - 1 Jan 2024

Cited by 1 | Viewed by 1705

Abstract

The research program “Engineered Artificial Minerals (EnAM)” addresses the challenge of recycling valuable elements from battery waste streams. These elements, such as lithium (Li), often migrate in the slag phase, in some cases as crystals. EnAM crystals represent concentrated reservoirs of these elements, [...] Read more.

The research program “Engineered Artificial Minerals (EnAM)” addresses the challenge of recycling valuable elements from battery waste streams. These elements, such as lithium (Li), often migrate in the slag phase, in some cases as crystals. EnAM crystals represent concentrated reservoirs of these elements, which can only be effectively recycled if they are extracted from the slag matrix and then separated. Selective wet agglomeration is a separation process based on a three-phase system and is often used in coal and ore processing. The produced agglomerates in this process can be easily separated from the remaining suspension. The precise quantification of the wetting properties and adhesion strength between suspended particles and binding liquid droplets is a scientific challenge. An accurate technique suitable for adhesion force measurements in three-phase systems with micrometer-scale particles is Fluidic Force Microscopy (FluidFM^®). An experimental setup with optical control is being developed to measure adhesion forces between droplets and flat/rough surfaces. This will enable precise measurements of adhesion forces between solid EnAM crystals and binding liquid droplets. Based on these measurements, optimal agglomeration conditions can be selected in the future to improve selective wet agglomeration with respect to recycling processes. Full article

(This article belongs to the Section Separation Processes)

► Show Figures

Figure 1

39 pages, 4112 KiB

Open AccessEditor’s ChoiceArticle

Extended Definition of Conversion and Reaction Extent for a Systematic Development of the Design Equations for Reactor Networks

by Alessio Caravella

Processes 2024, 12(1), 107; https://doi.org/10.3390/pr12010107 - 1 Jan 2024

Viewed by 1439

Abstract

The aim of this work is to present in a systematic way a novel general methodology to develop the design equations (heat and mass balances) for networks of ideal reactors, that is, Plug-Flow Reactors (PFRs) and Continuous Stirred Tank Reactors (CSTRs). In particular, [...] Read more.

The aim of this work is to present in a systematic way a novel general methodology to develop the design equations (heat and mass balances) for networks of ideal reactors, that is, Plug-Flow Reactors (PFRs) and Continuous Stirred Tank Reactors (CSTRs). In particular, after introducing the general definition of conversion to be used for reactor networks, several case studies of interest in chemical engineering are presented as topic-examples of application: (i) adiabatic-stage reactors with recycle, (ii) adiabatic-stage reactors with split, (iii) adiabatic-stage reactors intercooled by reactants and (iv) adiabatic-stage reactors with interstage distributed feed. More generally, the presented methodology can also be applied to develop the design equations for complex networks of interconnected reactors, not restricted to those considered in the present work. The motivation behind the present study lies in the fact that, to the best of our knowledge, a systematic development of the design equations of single reactors in reactor networks is currently missing in the open literature as well as in the reference textbooks of chemical reaction engineering and reactor design. Full article

(This article belongs to the Section Chemical Processes and Systems)

► Show Figures

Figure 1

20 pages, 4734 KiB

Open AccessEditor’s ChoiceArticle

Design and Characterization of a Melt Electrostatic Precipitator for Advanced Drug Formulations

by Anna Justen, Alina Faye Weltersbach, Gerhard Schaldach and Markus Thommes

Processes 2024, 12(1), 100; https://doi.org/10.3390/pr12010100 - 1 Jan 2024

Cited by 1 | Viewed by 1588

Abstract

Electrostatic precipitators (ESP) are especially known for the efficient separation of micron and submicron particles from aerosols. Wet electrostatic precipitators are particularly suitable for highly resistive materials. Using these, particles can be directly transferred into a liquid for further processing or safer handling, [...] Read more.

Electrostatic precipitators (ESP) are especially known for the efficient separation of micron and submicron particles from aerosols. Wet electrostatic precipitators are particularly suitable for highly resistive materials. Using these, particles can be directly transferred into a liquid for further processing or safer handling, which is advantageous for either hazardous or valuable materials. In this work, a wet ESP, which enables the separation of highly resistive particles into a heated liquid, was designed and investigated. To do this, spray-dried drug particles were embedded in a molten sugar alcohol to enhance the drug dissolution rate. After cooling, the solidified product showed advantageous properties such as a high drug dissolution rate and easy handling for further processing. For the design of the wet ESP, different discharge electrode configurations were tested. A wall film served as the collection electrode, which was generated by a specially designed distributer die. A laminar flow regime was achieved with a homogeneous film serving as the collection electrode, which is particularly important for a high separation efficiency. A prototype was designed and constructed in this respect. The particle separation into hot liquids or onto hot surfaces is challenging due to thermal effects in ESPs. The influence of thermophoresis and drag force on the particle transport was investigated, and optimum operation parameters were found for the present ESP. A broad field of applications can be covered with the presented device, where particles are embedded in even hot liquids to form liquid suspensions or, as it is presented here, solid dispersions. The dissolution of the drug-containing solid dispersion was studied in vitro. A remarkably faster drug dissolution was observed from the solid dispersion, as compared to a powder mixture of the drug and xylitol. Full article

► Show Figures

Figure 1

18 pages, 573 KiB

Open AccessEditor’s ChoiceArticle

Equation-Oriented Modeling and Optimization of a Biorefinery Based on Avocado Waste

by Daniel Sousa, Diogo Rodrigues, Pedro M. Castro and Henrique A. Matos

Processes 2024, 12(1), 91; https://doi.org/10.3390/pr12010091 - 30 Dec 2023

Cited by 6 | Viewed by 1514

Abstract

Due to the growth in the consumption of avocado in recent years, the amount of waste caused by avocado peel and seed has increased. Avocado waste can be transformed into valuable products such as energy, biofuels, and biological products using integrated processes in [...] Read more.

Due to the growth in the consumption of avocado in recent years, the amount of waste caused by avocado peel and seed has increased. Avocado waste can be transformed into valuable products such as energy, biofuels, and biological products using integrated processes in a biorefinery. This paper considers the detailed modeling, simulation, and optimization of a biorefinery for the production of phenolic compounds, bioethanol, biological xylitol, syngas, and electrical power from avocado seed and peel, using Aspen Plus in equation-oriented mode as a process simulation tool. For a biorefinery in nominal conditions, it is possible to achieve a gross profit of approximately

30 \times 10^{6}

USD/year for capital costs of USD

31.4 \times 10^{6}

, while the combined effect of process optimization and heat integration allows reaching a gross profit of

37 \times 10^{6}

USD/year for capital costs of USD

30.7 \times 10^{6}

. These results of the optimized plant show its potential to take advantage of avocado seed and peel in a profitable and sustainable way. This detailed equation-based model paves the way for superstructure optimization of a biorefinery for avocado waste processing. Full article

(This article belongs to the Special Issue Biorefinery and Thermochemical Conversion as Solutions for the Industrial Use of Agro-Industrial Residues)

► Show Figures

Figure 1

18 pages, 5233 KiB

Open AccessEditor’s ChoiceArticle

Alkaline Hydrothermal Treatment of Chabazite to Enhance Its Ammonium Removal and Recovery Capabilities through Recrystallization

by Dipshika Das and Sukalyan Sengupta

Processes 2024, 12(1), 85; https://doi.org/10.3390/pr12010085 - 29 Dec 2023

Cited by 1 | Viewed by 1439

Abstract

The treatment of chabazite (CHA), a natural zeolite, with the alkaline hydrothermal method to improve its ion-exchange capacity is a widely adopted route by environmental scientists for the purpose of better ammonium (

{N H}_{4}^{+}

) removal from wastewater. This work [...] Read more.

The treatment of chabazite (CHA), a natural zeolite, with the alkaline hydrothermal method to improve its ion-exchange capacity is a widely adopted route by environmental scientists for the purpose of better ammonium (

{N H}_{4}^{+}

) removal from wastewater. This work addresses a noteworthy trend in environmental science, where researchers, impressed by the increased ion-exchange capacity achieved through alkaline hydrothermal treatment, often bypass the thorough material characterization of treated CHA. The prevalent misconception attributes the improved features solely to the parent zeolitic framework, neglecting the fact that corrosive treatments like this can induce significant alterations in the framework and those must be identified with correct nomenclature. In this work, alkaline-mediated hydrothermally treated CHA has been characterized through X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS) and it is concluded that the treated samples have been transformed into a desilicated, aluminum (Al)-dense framework of analcime (ANA) with a low silica–alumina ratio and with a strikingly different crystal shape than that of parent CHA. This treated sample is further examined for its

{N H}_{4}^{+}

removal capacity from synthetic wastewater in a fixed-bed column arrangement. It achieved a maximum

{N H}_{4}^{+}

removal efficiency of 4.19 meq/g (75.6 mg/g of

{N H}_{4}^{+}

), twice that of the parent CHA. Moreover, the regeneration of the exhausted column yielded a regenerant solution, with 94% reclaimed

{N H}_{4}^{+}

in it, which could be used independently as a nitrogenous fertilizer. In this work, the meticulous compositional study of zeolitic materials, a well-established practice in the field of material science, is advocated for adoption by environmental chemists. By embracing this approach, environmental scientists can enhance their comprehension of the intricate changes induced by corrosive treatments, thereby contributing to a more nuanced understanding of zeolitic behavior in environmental contexts. Full article

(This article belongs to the Section Environmental and Green Processes)

► Show Figures

Figure 1

13 pages, 4748 KiB

Open AccessEditor’s ChoiceArticle

Au Nanoparticle-Loaded UiO-66 Metal–Organic Framework for Efficient Photocatalytic N₂ Fixation

by Zehui Zhao, Guangmin Ren, Xiangchao Meng and Zizhen Li

Processes 2024, 12(1), 64; https://doi.org/10.3390/pr12010064 - 27 Dec 2023

Cited by 2 | Viewed by 2351

Abstract

In order to achieve efficient photocatalytic N₂ reduction activity for ammonia synthesis, a photochemical strategy was used in this work. UiO-66 was prepared through the solvothermal method and further loaded with Au nanoparticles (Au NPs) onto the UiO-66 (Zr) framework. The experimental [...] Read more.

In order to achieve efficient photocatalytic N₂ reduction activity for ammonia synthesis, a photochemical strategy was used in this work. UiO-66 was prepared through the solvothermal method and further loaded with Au nanoparticles (Au NPs) onto the UiO-66 (Zr) framework. The experimental results verified that there were metal–support interactions between Au NPs and UiO-66; this could facilitate charge transfer among Au NPs and UiO-66, which was beneficial to enhance the photocatalytic activity. The best N₂ fixation effect of Au/UiO-66 with a loading of 1.5 wt% was tested, with a photocatalytic yield of ammonia of 66.28 μmol g⁻¹ h⁻¹ while maintaining good stability. The present work provides a novel approach to enhancing photocatalytic N₂ fixation activity by loading NPs onto UiO-66. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis Promoted by High Entropy Metal Oxides)

► Show Figures

Figure 1

15 pages, 2289 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A New Comprehensive Indicator for Monitoring Anaerobic Digestion: A Principal Component Analysis Approach

by Ru Jia, Young-Chae Song, Zhengkai An, Keugtae Kim, Chae-Young Lee and Byung-Uk Bae

Processes 2024, 12(1), 59; https://doi.org/10.3390/pr12010059 - 26 Dec 2023

Cited by 1 | Viewed by 1996

Abstract

This paper has proposed a comprehensive indicator based on principal component analysis (PCA) for diagnosing the state of anaerobic digestion. Various state and performance variables were monitored under different operational modes, including start-up, interruption and resumption of substrate supply, and impulse organic loading [...] Read more.

This paper has proposed a comprehensive indicator based on principal component analysis (PCA) for diagnosing the state of anaerobic digestion. Various state and performance variables were monitored under different operational modes, including start-up, interruption and resumption of substrate supply, and impulse organic loading rates. While these individual variables are useful for estimating the state of anaerobic digestion, they must be interpreted by experts. Coupled indicators combine these variables with the effect of offering more detailed insights, but they are limited in their universal applicability. Time-series eigenvalues reflected the anaerobic digestion process occurring in response to operational changes: Stable states were identified by eigenvalue peaks below 1.0, and they had an average below 0.2. Slightly perturbed states were identified by a consistent decrease in eigenvalue peaks from a value of below 4.0 or by observing isolated peaks below 3.0. Disturbed states were identified by repeated eigenvalue peaks over 3.0, and they had an average above 0.6. The long-term persistence of these peaks signals an increasing kinetic imbalance, which could lead to process failure. Ultimately, this study demonstrates that time-series eigenvalue analysis is an effective comprehensive indicator for identifying kinetic imbalances in anaerobic digestion. Full article

(This article belongs to the Special Issue Anaerobic Processes, Monitoring and Intelligence Control)

► Show Figures

Graphical abstract

13 pages, 4314 KiB

Open AccessEditor’s ChoiceArticle

Hydrodynamics and Mass Transfer in an Airlift Loop Reactor: Comparison between Using Two Kinds of Spargers

by Xiao Xu and Yingchun Zhang

Processes 2024, 12(1), 35; https://doi.org/10.3390/pr12010035 - 22 Dec 2023

Cited by 5 | Viewed by 2181

Abstract

The effects of different spargers on the hydrodynamics and mass transfer of an airlift loop reactor were investigated. The gas holdup, liquid loop velocity, and volumetric mass transfer coefficient of the reactor were tested using a ring orifice distributor and a jet nozzle. [...] Read more.

The effects of different spargers on the hydrodynamics and mass transfer of an airlift loop reactor were investigated. The gas holdup, liquid loop velocity, and volumetric mass transfer coefficient of the reactor were tested using a ring orifice distributor and a jet nozzle. The study was conducted in a 6 m high airlift loop reactor at a superficial gas velocity of 0.01~0.04 m/s, and the superficial liquid velocity was maintained at 0.0154 m/s. The results showed that using the jet nozzle provided a higher gas holdup, liquid loop velocity, and mass transfer. When the superficial gas velocity was less than 0.0325 m/s, the liquid loop velocity generated by the jet nozzle was approximately 1.1-fold higher than that generated by the ring orifice distributor, and the disparity in gas holdup between the riser and downcomer enhanced the power of liquid circulation. When the superficial gas velocity was more than 0.0325 m/s, the jet kinetic power dominated the improvement in the liquid loop velocity, and the energy input from the nozzle to the airlift loop reactor was greater than 10.8 J/(s·m²). This indicated a threshold of energy input for overcoming the friction loss. In this situation, the liquid loop velocity in the jet form increased considerably, thus favoring the mixing performance and temperature uniformity of the reactor. It was also of significance for avoiding the formation of a flow dead zone in scale-up airlift loop reactors. Full article

(This article belongs to the Section Chemical Processes and Systems)

► Show Figures

Figure 1

23 pages, 3097 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Industrial Data-Driven Processing Framework Combining Process Knowledge for Improved Decision-Making—Part 2: Framework Application Considering Activity-Based Costing Concepts

by Émilie Thibault, Christian Ledoux and Paul Stuart

Processes 2024, 12(1), 26; https://doi.org/10.3390/pr12010026 - 21 Dec 2023

Viewed by 1296

Abstract

Operating time series data collected and stored in historian must be managed to extract their full potential. Part 1 of this paper proposed a structured way (a sophisticated approach) to process industrial data; this first part explains in detail the data processing framework [...] Read more.

Operating time series data collected and stored in historian must be managed to extract their full potential. Part 1 of this paper proposed a structured way (a sophisticated approach) to process industrial data; this first part explains in detail the data processing framework used as the basis for the costing analysis present in the second part of this series. The framework considers the analysis scope definition, data management steps, and operating regimes detection and identification. The added value of this proposed framework is demonstrated in Part 2 via the use of cost accounting for operational problem-solving (debottlenecking), i.e., its practicality is validated via its application alongside a cost analysis on the brownstock washing department of a kraft pulp mill. The traditional debottlenecking approach assumes a single operating condition considering that operating regimes allow for a much more sophisticated debottlenecking study of the washing department. With the use of operations-driven cost modeling (contingent on activity-based costing concepts) and processed time series data corresponding to steady-state operation, incremental profit can be assigned to each operating regime in order to identify the most cost-efficient one. The overall objective of this two-part series is to convert processed industrial steady-state data and cost information into knowledge that can be used to optimize the washing department of a chemical pulp mill. More specifically, different operating regimes are assessed, and the most suitable operating strategy is defined. The application of activity-based costing on a large amount of historically processed industrial data led to the improvement in the operation. The identified optimal way to operate (pulp throughput, pulp conductivity, defoamer and bleaching chemical quantity, etc.) led to a profit of CAD 49 M per year. Lastly, a contribution analysis of the regimes based on PCA highlighted how the process was operated when the preferred performances happened. Full article

(This article belongs to the Section Process Control and Monitoring)

► Show Figures

Figure 1

21 pages, 6257 KiB

Open AccessEditor’s ChoiceArticle

Wastewater Treatment Using Shear Enhanced Flotation Separation Technology: A Pilot Plant Study for Winery Wastewater Processing

by David Vlotman, David Key, Bradley Cerff and Bernard Jan Bladergroen

Processes 2024, 12(1), 3; https://doi.org/10.3390/pr12010003 - 19 Dec 2023

Cited by 3 | Viewed by 2050

Abstract

The agricultural sector is one that requires and consumes enormous amounts of fresh water globally. Commercial wine production in particular uses large volumes of fresh water and, through various processes, generates significant quantities of wastewater. The wastewater produced by wineries typically exhibits elevated [...] Read more.

The agricultural sector is one that requires and consumes enormous amounts of fresh water globally. Commercial wine production in particular uses large volumes of fresh water and, through various processes, generates significant quantities of wastewater. The wastewater produced by wineries typically exhibits elevated levels of chemical oxygen demand (COD), total suspended solids (TSS), an acidic pH, and varying salinity and nutrient contents. The overall characteristics of winery wastewater indicate that it is a potential environmental hazard if not processed and disposed of appropriately. Due to significant variations in wastewater contaminant levels among wineries, the implementation of a universally applicable, environmentally friendly, and sustainable waste management system seems practically unattainable. This study investigated the design, fabrication, and modification of a shear enhanced flotation separation (SEFS) pilot plant to be used as a primary treatment stage during winery wastewater processing. This technology combines the synergistic advantages of hydrodynamic shear, coagulation, flocculation, and dissolved air flotation. To date, there have been only limited publications on the feasibility and application of hydrodynamic shear and its potential to assist with coagulation/flocculation and flotation efficiencies specifically for winery wastewater treatment. The results obtained indicate that the SEFS pilot plant may well be able to process winery wastewater to a quality level where reuse of the water for irrigation of crops may be considered. Full article

(This article belongs to the Special Issue Separation Processes for Environmental Preservation)

► Show Figures

Figure 1

16 pages, 2867 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synthesis of 2,6-Dihydroxybenzoic Acid by Decarboxylase-Catalyzed Carboxylation Using CO₂ and In Situ Product Removal

by Daniel Ohde, Benjamin Thomas, Paul Bubenheim and Andreas Liese

Processes 2024, 12(1), 10; https://doi.org/10.3390/pr12010010 - 19 Dec 2023

Cited by 1 | Viewed by 1760

Abstract

For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO₂ in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. [...] Read more.

For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO₂ in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. First, a screening for a high-affinity adsorber was carried out. Then, the application of a suitable adsorber was successfully demonstrated. This enabled achieving reaction yields above 80% using the adsorber for in situ product removal. The applied biotransformation was scaled up to 1.5 L at lab-scale. Furthermore, a downstream process based on the elution and purification of the product bound to the adsorber was developed to obtain 2,6-DHBA in high purity. Recycling is one of the key factors in this system, making it possible to recycle the reaction medium, the adsorber and the solvents in additional batches. Full article

(This article belongs to the Special Issue Development, Modelling and Simulation of Biocatalytic Processes)

► Show Figures

Graphical abstract

18 pages, 3855 KiB

Open AccessEditor’s ChoiceArticle

Numerical Prediction of Refrigerant Oil Two-Phase Flow from Scroll Compressor Discharge to the Suction Side via Back Pressure Chamber

by Vladimir D. Stevanovic, Milan M. Petrovic, Stojan Cucuz, Sanja Milivojevic and Milica Ilic

Processes 2024, 12(1), 6; https://doi.org/10.3390/pr12010006 - 19 Dec 2023

Cited by 1 | Viewed by 1407

Abstract

Oil lubricates the contact between the orbiting and stationary scroll in the refrigerant scroll compressor, while the sealing between the scrolls is achieved through the refrigerant vapour pressure in the sealed back pressure chamber. The back pressure should be adjusted using the refrigerant [...] Read more.

Oil lubricates the contact between the orbiting and stationary scroll in the refrigerant scroll compressor, while the sealing between the scrolls is achieved through the refrigerant vapour pressure in the sealed back pressure chamber. The back pressure should be adjusted using the refrigerant oil two-phase flow from the oil separator at the compressor discharge to the back pressure chamber and the refrigerant oil flow from the back pressure chamber to the compressor suction side. Both of the flows are conducted through connecting tubes with corresponding high-pressure and low-pressure nozzles with small diameters. Models for predicting the refrigerant oil critical and subcritical flows through the nozzles were developed and applied in enable the prediction of the back pressure. The models are original, because the slip between the oil and the refrigerant as well as the refrigerant solubility in the oil are taken into account. The critical flow model is validated against the experimental data that are available in the literature. The back pressure is predicted by equating the mass flow rates of refrigerant and oil two-phase mixtures through the high- and low-pressure nozzles. The results show that the critical flow takes place through the high-pressure nozzle, while the subcritical flow through the low-pressure nozzle can also exist in cases with a small pressure difference between the back pressure chamber and the compressor suction side. The refrigerant solubility in the oil has a small influence on the critical and subcritical refrigerant oil mixture mass flow rates, while the influence on the back pressure is more pronounced. Full article

(This article belongs to the Section Energy Systems)

► Show Figures

Figure 1

15 pages, 4584 KiB

Open AccessEditor’s ChoiceArticle

Development of a Calibration Model for Real-Time Solute Concentration Monitoring during Crystallization of Ceritinib Using Raman Spectroscopy and In-Line Process Microscopy

by Matea Gavran, Željka Ujević Andrijić, Nenad Bolf, Nikola Rimac, Josip Sacher and Damir Šahnić

Processes 2023, 11(12), 3439; https://doi.org/10.3390/pr11123439 - 16 Dec 2023

Cited by 2 | Viewed by 1677

Abstract

Raman spectroscopy is a useful tool for polymorphic form-monitoring during the crystallization process. However, its application to solute concentration estimation in two-phase systems like crystallization is rare, as the Raman signal is influenced by various changing factors in the crystallization process. The development [...] Read more.

Raman spectroscopy is a useful tool for polymorphic form-monitoring during the crystallization process. However, its application to solute concentration estimation in two-phase systems like crystallization is rare, as the Raman signal is influenced by various changing factors in the crystallization process. The development of a robust calibration model that covers all variations is complex and represents a major challenge for the implementation of Raman spectroscopy for in-line monitoring and control of the solution crystallization process. This paper describes the development of a Raman-based calibration model for estimating the solute concentration of the active pharmaceutical ingredient ceritinib. Several different calibration approaches were tested, which included both temperature and spectra of clear solutions and slurries/suspensions. It was found that the concentration of the ceritinib solution could not be accurately predicted when suspended crystals were present. To overcome this challenge, the approach was enhanced by including additional variables related to crystal size and solid concentration obtained via in-line process microscopy (chord-length distribution percentiles D10, D50 and D90) and turbidity. Partial least squares regression (PLSR) and artificial neural network (ANN) models were developed and compared based on root mean square error (RMSE). ANN models estimated the solute concentration with high accuracy, with the prediction error not exceeding 1% of the nominal solute concentration. Full article

(This article belongs to the Section Process Control and Monitoring)

► Show Figures

Figure 1

31 pages, 2120 KiB

Open AccessEditor’s ChoiceReview

Emerging Trends in Green Extraction Techniques for Bioactive Natural Products

by Muhammad Usman, Mayuko Nakagawa and Shuo Cheng

Processes 2023, 11(12), 3444; https://doi.org/10.3390/pr11123444 - 16 Dec 2023

Cited by 49 | Viewed by 12209

Abstract

This review explores eco-friendly methods for extracting bioactive natural products from diverse sources. The introductory exploration emphasizes the increasing demand for sustainable extraction methods, with a focus on the environmental impact of conventional approaches. Addressing existing knowledge gaps, this review outlines the key [...] Read more.

This review explores eco-friendly methods for extracting bioactive natural products from diverse sources. The introductory exploration emphasizes the increasing demand for sustainable extraction methods, with a focus on the environmental impact of conventional approaches. Addressing existing knowledge gaps, this review outlines the key objectives of evaluating various green extraction technologies, including supercritical fluid extraction, pressurized liquid extraction, ultrasound-assisted extraction, enzyme-assisted extraction, and others. The primary findings underscore the remarkable potential and advancements achieved with green solvents, specifically deep eutectic solvents and bio-based solvents. This review elucidates the synergistic effects achieved by combining different extraction techniques, exemplified by ultrasound-microwave-assisted extraction and sequential supercritical fluid and pressurized liquid extraction, among others. Notwithstanding the promising results, this review emphasizes the importance of acknowledging and addressing challenges such as standardization, selectivity, scalability, and economic viability. Full article

(This article belongs to the Special Issue Innovations in Green Separation and Extraction Processes of Natural Products)

► Show Figures

Graphical abstract

18 pages, 6948 KiB

Open AccessEditor’s ChoiceArticle

A Fault Detection and Isolation Method via Shared Nearest Neighbor for Circulating Fluidized Bed Boiler

by Minseok Kim, Seunghwan Jung, Eunkyeong Kim, Baekcheon Kim, Jinyong Kim and Sungshin Kim

Processes 2023, 11(12), 3433; https://doi.org/10.3390/pr11123433 - 15 Dec 2023

Cited by 2 | Viewed by 1311

Abstract

Accurate and timely fault detection and isolation (FDI) improve the availability, safety, and reliability of target systems and enable cost-effective operations. In this study, a shared nearest neighbor (SNN)-based method is proposed to identify the fault variables of a circulating fluidized bed boiler. [...] Read more.

Accurate and timely fault detection and isolation (FDI) improve the availability, safety, and reliability of target systems and enable cost-effective operations. In this study, a shared nearest neighbor (SNN)-based method is proposed to identify the fault variables of a circulating fluidized bed boiler. SNN is a derivative method of the k-nearest neighbor (kNN), which utilizes shared neighbor information. The distance information between these neighbors can be applied to FDI. In particular, the proposed method can effectively detect faults by weighing the distance values based on the number of neighbors they share, thereby readjusting the distance values based on the shared neighbors. Moreover, the data distribution is not constrained; therefore, it can be applied to various processes. Unlike principal component analysis and independent component analysis, which are widely used to identify fault variables, the main advantage of SNN is that it does not suffer from smearing effects, because it calculates the contributions from the original input space. The proposed method is applied to two case studies and to the failure case of a real circulating fluidized bed boiler to confirm its effectiveness. The results show that the proposed method can detect faults earlier (1 h 39 min 46 s) and identify fault variables more effectively than conventional methods. Full article

(This article belongs to the Special Issue 10th Anniversary of Processes—Recent Advances in Process Control and Monitoring)

► Show Figures

Figure 1

14 pages, 2755 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Rigid Polyurethane Foams Modified with Soybean-Husk-Derived Ash as Potential Insulating Materials

by Anna Magiera, Monika Kuźnia, Aleksandra Błoniarz and Aneta Magdziarz

Processes 2023, 11(12), 3416; https://doi.org/10.3390/pr11123416 - 13 Dec 2023

Cited by 3 | Viewed by 1749

Abstract

One of the most popular polymeric materials in the building and construction industry is rigid polyurethane foam (RPUF). In order to reduce the number of expensive chemical components, various fillers are used in the RPUF industry. The aim of this work was to [...] Read more.

One of the most popular polymeric materials in the building and construction industry is rigid polyurethane foam (RPUF). In order to reduce the number of expensive chemical components, various fillers are used in the RPUF industry. The aim of this work was to investigate the influence of the biomass originated filler soybean-husk-derived ash on the structure and properties of composite RPUF. Firstly, polyurethane foams were obtained using hand mixing and casting techniques. Composite foams contained 5, 10, 15, and 20 wt. % of the filler. Secondly, the obtained composite materials were analyzed considering their cellular structure using optical microscopy and image processing software. All samples were composed of mostly pentagonal, regular-in-shape cells. Their diameters ranged between 100 and 70 µm. The chemical structure of the foams was investigated using infrared spectroscopy. No chemical interactions between matrix and filler were detected. Mechanical testing was performed in order to evaluate the mechanical performance of the materials. Both compressive strength and Young’s modulus were comparable and equaled approx. 130 kPa and 2.5 MPa, respectively. Wettability analysis indicated a hydrophobic nature of the materials. The obtained results suggested that the cellular and chemical structure of the polyurethane matrix was not affected by the filler incorporation. Full article

► Show Figures

Figure 1

19 pages, 4394 KiB

Open AccessEditor’s ChoiceArticle

Use of Simulated Sunlight Radiation and Hydrogen Peroxide to Remove Xenobiotics from Aqueous Solutions

by Bruna Babić Visković, Anamaria Maslač, Davor Dolar and Danijela Ašperger

Processes 2023, 11(12), 3403; https://doi.org/10.3390/pr11123403 - 11 Dec 2023

Viewed by 1313

Abstract

Xenobiotics, which include a wide range of synthetic chemicals and compounds, have become a significant threat to water quality and biodiversity. The need for innovative and sustainable solutions to mitigate the impact of pollutants on our ecosystems has become a hot topic of [...] Read more.

Xenobiotics, which include a wide range of synthetic chemicals and compounds, have become a significant threat to water quality and biodiversity. The need for innovative and sustainable solutions to mitigate the impact of pollutants on our ecosystems has become a hot topic of numerous discussions and research. One such solution lies in the potential application of simulated solar radiation and hydrogen peroxide to remove pesticides from aqueous solutions. In this paper, we investigated the possibility of removing selected pesticides (acetamiprid, clothianidin, and thiacloprid) under the influence of simulated solar radiation with and without the presence of hydrogen peroxide (H₂O₂). The influence of pH value and H₂O₂ concentration on removal and toxicity before and after photolytic removal was examined. The results showed that clothianidin is almost completely removed (94.80–96.35%) after 5 h under the influence of simulated solar radiation, while thiacloprid and acetamiprid confirm their persistence and resistance to photolytic degradation. The addition of H₂O₂ leads to the removal of all three pesticides and results in a significant acceleration of the degradation process itself and the removal of the individual pesticides already within 2 h. According to the data obtained, the k values obtained in the paper follow the following trend: clothianidin > thiacloprid > acetamiprid. Full article

(This article belongs to the Special Issue Catalysis in Advanced Oxidation Processes for Environmental Remediation)

► Show Figures

Figure 1

19 pages, 5693 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analyzing Local Shear Rate Distribution in a Dual Coaxial Mixing Bioreactor Handling Herschel–Bulkley Biopolymer Solutions through Computational Fluid Dynamics

by Forough Sharifi, Ehsan Behzadfar and Farhad Ein-Mozaffari

Processes 2023, 11(12), 3387; https://doi.org/10.3390/pr11123387 - 7 Dec 2023

Cited by 4 | Viewed by 1629

Abstract

For the aeration of highly viscous non-Newtonian fluids, prior studies have demonstrated the improved efficacy of dual coaxial mixing bioreactors fitted with two central impellers and a close clearance anchor. Evaluating the effectiveness of these bioreactors involves considering various mixing characteristics, with a [...] Read more.

For the aeration of highly viscous non-Newtonian fluids, prior studies have demonstrated the improved efficacy of dual coaxial mixing bioreactors fitted with two central impellers and a close clearance anchor. Evaluating the effectiveness of these bioreactors involves considering various mixing characteristics, with a specific emphasis on shear rate distribution. The study of shear rate distribution is critical due to its significant impact on the mixing performance, gas dispersion, and homogeneity in aerated mixing systems comprising shear-thinning fluids. Although yield-pseudoplastic fluids are commonly employed in various industries, there is a research gap when it comes to evaluating shear rate distribution in aerated mixing bioreactors that utilize this fluid type. This study aims to investigate shear rate distribution in an aerated double coaxial bioreactor that handles a 1 wt% xanthan gum solution, known as a Herschel–Bulkley fluid. To achieve this goal, we employed an experimentally validated computational fluid dynamics (CFD) model to assess the effect of different mixing configurations, including down-pumping and co-rotating (Down-Co), up-pumping and co-rotating (Up-Co), down-pumping and counter-rotating (Down-Counter), and up-pumping and counter-rotating (Up-Counter) modes, on the shear rate distribution within the coaxial mixing bioreactor. Our findings revealed that the Up-Co system led to a more uniform local shear distribution and improved mixing performance. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Electronic Conference on Processes: Process Engineering—Current State and Future Trends (ECP2023))

► Show Figures

Figure 1

22 pages, 2553 KiB

Open AccessEditor’s ChoiceArticle

Maximizing the Recovery of Phenolic Antioxidants from Wild Strawberry (Fragaria vesca) Leaves Using Microwave-Assisted Extraction and Accelerated Solvent Extraction

by Petra Terpinc, Erika Dobroslavić, Ivona Elez Garofulić, Maja Repajić, Ena Cegledi, Ana Dobrinčić, Sandra Pedisić and Branka Levaj

Processes 2023, 11(12), 3378; https://doi.org/10.3390/pr11123378 - 6 Dec 2023

Cited by 4 | Viewed by 1967

Abstract

Due to the presence of diverse phenolic classes in wild strawberry (Fragaria vesca L.) leaves, there is an ever-growing effort to find new, efficient methods for their recovery and detailed characterization. Microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) were evaluated to [...] Read more.

Due to the presence of diverse phenolic classes in wild strawberry (Fragaria vesca L.) leaves, there is an ever-growing effort to find new, efficient methods for their recovery and detailed characterization. Microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) were evaluated to understand the impact of the extraction temperature, extraction time, and solvent-to-sample ratio (SSR) on the quantitative and qualitative properties of the obtained extracts. The highest total phenolic content (8027 mg GA/100 g DW), as well as the highest DPPH^• antiradical activity (903 μmol TE/g DW), was obtained with ASE at 150 °C with a static time of 5 min and an SSR of 40:1, while the highest ABTS^•+ antiradical activity (681 μmol TE/g DW) and FRAP (2389 μmol TE/g DW) were obtained with MAE after 5 min at 80 °C and an SSR of 40:1. A total of 54 different phenolics were identified by UPLC/MS-MS, some for the first time. The MAE extract had a higher content of phenolic acids (40%; esp. p-hydroxybenzoic acid, gallic acid) and myricetin, while the ASE extract was richer in proanthocyanidins (88%; esp. procyanidin B1, procyanidin trimer), flavonols (29%; esp. quercetin, quercetin-3-glucuronide, rutin), flavan-3-ols (50%; esp. epicatechin), and flavones (39%; esp. luteolin). The results indicated that for optimal extraction conditions, the target phenolics and the desired antioxidant properties of the obtained extracts should be considered. Full article

(This article belongs to the Special Issue Separation and Extraction Techniques in Food Processing and Analysis)

► Show Figures

Figure 1

19 pages, 1708 KiB

Open AccessEditor’s ChoiceArticle

Panoramic Semiquantitave Analysis for Multielement Characterization of Liquid and Solid Waste Samples

by Valentina Lyubomirova, Iva Belovezhdova, Rumyana Djingova, Petar Petrov and Ekaterina Todorova

Processes 2023, 11(12), 3379; https://doi.org/10.3390/pr11123379 - 6 Dec 2023

Cited by 1 | Viewed by 1080

Abstract

Wastewater treatment results in large amounts of sewage sludge in the wastewater treatment plant (WWTP) which imposes on its reuse. The most promising application is as a fertilizer in agriculture which is regulated by national and European legislation. Along with the mandatory determination [...] Read more.

Wastewater treatment results in large amounts of sewage sludge in the wastewater treatment plant (WWTP) which imposes on its reuse. The most promising application is as a fertilizer in agriculture which is regulated by national and European legislation. Along with the mandatory determination of potentially toxic elements (PTEs), in order to assess not only the risks, but also the beneficial properties, the determination of the total chemical composition is desirable. Inductively coupled plasma mass spectrometry (ICP-MS) is the most promising technique for multielement characterization which can be applied both for quantitative and semiquantitative analysis. A significant difference between the approaches is that the semiquantitative analysis is performed after a calibration with one standard solution containing at least three elements, but, at the same time, the accuracy is worse. In the present work, the accuracy of semiquantitative analysis with a different number of calibration elements using both water standard solutions and certified reference material (CRM) for calibration was investigated for the determination of 69 elements in sewage sludge CRMs and samples. It has been found that the accuracy can vary within a wide range, depending on the concentration of the elements, the number of calibration elements, and/or the presence of neighboring masses. In order to obtain an accuracy of up to 30%, it is recommended to shorten the mass intervals and perform the calibration with at least 18 elements, mainly microelements. The method was applied for fast panoramic analysis of sewage sludge samples from WWTPs and the concentrations were close to the data from quantitative analysis. Full article

(This article belongs to the Special Issue Innovations in Sewage Treatment Focused on Global Environmental Challenges)

► Show Figures

Figure 1

17 pages, 2998 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Modelling and Optimization of Methylene Blue Adsorption Process on Leonurus cardiaca L. Biomass Powder

by Giannin Mosoarca, Simona Popa, Cosmin Vancea, Mircea Dan and Sorina Boran

Processes 2023, 11(12), 3385; https://doi.org/10.3390/pr11123385 - 6 Dec 2023

Cited by 3 | Viewed by 1792

Abstract

The main objective of this study was to optimize the adsorption process of methylene blue on a natural, low-cost adsorbent, Leonurus cardiaca L. biomass powder, in order to maximize dye removal efficiency from aqueous solutions. For this purpose, the Taguchi method was used [...] Read more.

The main objective of this study was to optimize the adsorption process of methylene blue on a natural, low-cost adsorbent, Leonurus cardiaca L. biomass powder, in order to maximize dye removal efficiency from aqueous solutions. For this purpose, the Taguchi method was used based on an L₂₇ orthogonal array design considering six controllable factors at three levels. The percentage contribution of each factor was computed using analysis of variance (ANOVA). The optimal adsorption conditions were established. The experimental data from equilibrium and kinetic studies were modelled using specific equilibrium isotherms and kinetic models. Thermodynamic parameters were calculated in order to determine the main adsorption mechanism. The obtained results showed that the ionic strength is the factor that most influences dye adsorption (percentage contribution 72.33%), whereas the adsorbent dose had the least impact. The Sips isotherm and the general kinetic model most accurately characterized the process. The maximum adsorption capacity 103.21 (mg g⁻¹) indicated by the Sips isotherm and the equilibrium time (40 min) were better compared to the values obtained for other bio-adsorbents used for methylene blue adsorption. The main mechanism involved in the adsorption is physisorption, while chemisorption only contributes marginally to the process. Full article

(This article belongs to the Special Issue Advances in Adsorption of Wastewater Pollutants)

► Show Figures

Figure 1

14 pages, 3147 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Effect of Hollow Glass Microspheres on the Kinetics of Oxidation of Poly(ε-Caprolactone) Determined from Non-Isothermal Thermogravimetry and Chemiluminescence

by Anna Vykydalová, Zdenko Špitálský, Mária Kováčová and Jozef Rychlý

Processes 2023, 11(12), 3372; https://doi.org/10.3390/pr11123372 - 5 Dec 2023

Viewed by 1314

Abstract

The effect of hollow glass beads on poly(ε-caprolactone) (PCL) oxidative degradation has been evaluated by the non-isothermal chemiluminescence (CL) method and thermogravimetry analysis (TGA). The main goal of the research and this publication was to reduce the production costs associated with the materials [...] Read more.

The effect of hollow glass beads on poly(ε-caprolactone) (PCL) oxidative degradation has been evaluated by the non-isothermal chemiluminescence (CL) method and thermogravimetry analysis (TGA). The main goal of the research and this publication was to reduce the production costs associated with the materials for 3D printing, which would also have a low mass, excellent biocompatibility and suitable thermal properties. Experiments have clearly shown the dual effect of a filler and its extent in terms of poly(ε-caprolactone). The chosen methods demonstrate the superposition of both the pro-degradation and stabilization effects of hollow glass beads on the polymer. The former was evident above the load of 10 wt.% of filler. The non-isothermal TGA records were analyzed as being composed of three temperature-dependent processes of the first-order kinetics. A massive compensation effect between the so-called activation energy and the logarithm of pre-exponential factors for heating rates of 2.5, 5 and 10 °C/min has been shown to be typical for similar non-isothermal thermogravimetry evaluation. Full article

(This article belongs to the Special Issue Processes in 2023)

► Show Figures

Graphical abstract

12 pages, 13717 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Physicochemical Characterization of Potassium Hydroxide Pretreated Chestnut Shell and Its Bioconversion to Lactic Acid by Lacticaseibacillus rhamnosus

by Jeongho Lee, Seunghee Kim, Hyerim Son, Kang Hyun Lee, Chulhwan Park and Hah Young Yoo

Processes 2023, 11(12), 3340; https://doi.org/10.3390/pr11123340 - 30 Nov 2023

Cited by 5 | Viewed by 1861

Abstract

Lactic acid (LA) is an important platform chemical with a wide range of applications, including bioplastic materials, and demand for it is growing rapidly. However, the high cost of feedstock for LA production is a major barrier to industrial production. This study designed [...] Read more.

Lactic acid (LA) is an important platform chemical with a wide range of applications, including bioplastic materials, and demand for it is growing rapidly. However, the high cost of feedstock for LA production is a major barrier to industrial production. This study designed a process to produce LA from chestnut shell (CS), a low-cost biomass. The entire process includes KOH pretreatment, enzymatic saccharification, and fermentation. This study investigated the chemical compositions and physicochemical properties of raw CS and KOH pretreated CS (KpCS) to evaluate the impact of the pretreatment process that enhances the conversion of cellulose into glucose. The results showed that KOH affected the lignin removal and surface morphological changes of CS, and FT-IR and TGA patterns correlated to increased cellulose fractions were found. In the fermentation process, Lacticaseibacillus rhamnosus was selected as a prominent LA producer, and the fermentation using KpCS hydrolysate was carried out. As a result, cell growth (27%), glucose consumption (23%), and LA production (21%) were all achieved higher than the control group. The LA production yield from our suggested process was estimated to be 187 g/kg CS, and we concluded that CS has a high potential as a feedstock for LA production. Full article

(This article belongs to the Special Issue Green and Sustainable Chemistry of Waste Conversion in Circular Economy: Challenges and Perspectives)

► Show Figures

Graphical abstract

14 pages, 1217 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Biodegradation and Utilization of the Pesticides Glyphosate and Carbofuran by Two Yeast Strains

by Katya Stoyanova, Maria Gerginova, Nadejda Peneva, Ivayla Dincheva and Zlatka Alexieva

Processes 2023, 11(12), 3343; https://doi.org/10.3390/pr11123343 - 30 Nov 2023

Cited by 5 | Viewed by 2184

Abstract

The widespread use of synthetic pesticides in agricultural practice is associated with the risk of environmental pollution, damage to non-target organisms, and harm to the health of consumers due to the presence of pesticides in the resulting products. Metabolically active microbial species play [...] Read more.

The widespread use of synthetic pesticides in agricultural practice is associated with the risk of environmental pollution, damage to non-target organisms, and harm to the health of consumers due to the presence of pesticides in the resulting products. Metabolically active microbial species play a significant role in eliminating harmful chemicals from the environment. The two yeast strains used in this study are Trichosporon cutaneum R57 and Candida tropicalis V1. Both strains showed growth and development in the presence of the pesticides glyphosate and carbofuran used as the sole carbon sources. The gas-chromatographic analysis performed showed that C. tropicalis V1 reached 76% of 0.3 g/L glyphosate biodegradation in 192 h. At the same time, the amount of glyphosate decreased by about 58% in the culture of T. cutaneum R57. During the glyphosate biodegradation process, the presence of the intermediate metabolites methylglycine and glycine was revealed. Strain T. cutaneum R57 demonstrated nearly total biodegradation of 0.3 g/L carbofuran in 192 h of cultivation. Strain C. tropicalis V1 showed a slow decrease (23.4%) of the same amount of carbofuran during 192 h. Pyruvic acid and carbofuran-7-phenol have been found to be intermediate metabolites in the breakdown of carbofuran. This report provides new information on the potential of yeasts to participate in environmental pesticide cleanup processes. Full article

(This article belongs to the Special Issue Innovations in Sewage Treatment Focused on Global Environmental Challenges)

► Show Figures

Figure 1

40 pages, 5558 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

On the Development of Descriptor-Based Machine Learning Models for Thermodynamic Properties: Part 1—From Data Collection to Model Construction: Understanding of the Methods and Their Effects

by Cindy Trinh, Youssef Tbatou, Silvia Lasala, Olivier Herbinet and Dimitrios Meimaroglou

Processes 2023, 11(12), 3325; https://doi.org/10.3390/pr11123325 - 29 Nov 2023

Cited by 5 | Viewed by 3149

Abstract

In the present work, a multi-angle approach is adopted to develop two ML-QSPR models for the prediction of the enthalpy of formation and the entropy of molecules, in their ideal gas state. The molecules were represented by high-dimensional vectors of structural and physico-chemical [...] Read more.

In the present work, a multi-angle approach is adopted to develop two ML-QSPR models for the prediction of the enthalpy of formation and the entropy of molecules, in their ideal gas state. The molecules were represented by high-dimensional vectors of structural and physico-chemical characteristics (i.e., descriptors). In this sense, an overview is provided of the possible methods that can be employed at each step of the ML-QSPR procedure (i.e., data preprocessing, dimensionality reduction and model construction) and an attempt is made to increase the understanding of the effects related to a given choice or method on the model performance, interpretability and applicability domain. At the same time, the well-known OECD principles for the validation of (Q)SAR models are also considered and addressed. The employed data set is a good representation of two common problems in ML-QSPR modeling, namely the high-dimensional descriptor-based representation and the high chemical diversity of the molecules. This diversity effectively impacts the subsequent applicability of the developed models to a new molecule. The data set complexity is addressed through customized data preprocessing techniques and genetic algorithms. The former improves the data quality while limiting the loss of information, while the latter allows for the automatic identification of the most important descriptors, in accordance with a physical interpretation. The best performances are obtained with Lasso linear models (

M A E

test = 25.2 kJ/mol for the enthalpy and 17.9 J/mol/K for the entropy). Finally, the overall developed procedure is also tested on various enthalpy and entropy related data sets from the literature to check its applicability to other problems and competing performances are obtained, highlighting that different methods and molecular representations can lead to good performances. Full article

► Show Figures

Figure 1

11 pages, 2556 KiB

Open AccessEditor’s ChoiceArticle

Rheological Characterization of Gofio and Aloe Vera Blended Juice

by Francisco José Rubio-Hernández, Julia Rubio-Merino and Elvira García-López

Processes 2023, 11(12), 3315; https://doi.org/10.3390/pr11123315 - 28 Nov 2023

Viewed by 1345

Abstract

Considering that gofio (Gf) and aloe vera juice (AVJ) have very good nutritional qualities, their combination is proposed because it is indicated as an easy and fast source of basic bio-elements. The texture of a food must be accepted by customers. This means [...] Read more.

Considering that gofio (Gf) and aloe vera juice (AVJ) have very good nutritional qualities, their combination is proposed because it is indicated as an easy and fast source of basic bio-elements. The texture of a food must be accepted by customers. This means that the rheological characteristics of the product must be known and controlled. Therefore, the influence of Gf concentration on the rheological behavior of Gf/AVJ suspensions must be determined. With continuous shear experiments, the purely viscous response of a material can be obtained. AVJ and Gf/AVJ suspensions showed shear-thinning behavior. The ability of Gf particles and aggregates to distort the flow field was quantified determining the intrinsic viscosity

([η])

of the suspensions at several shear rates using Krieger–Dougherty equation. The results indicated that the shape and size of Gf aggregates is not affected by the mechanical action due to shear. The power law (Ostwald–de Waele) model fitted the experimental steady viscosity versus shear rate values (steady viscosity curves). The flow index was less than

1

, which corresponded to shear-thinning behavior. It was obtained that the flow index of AVJ maintained unaltered despite the presence of Gf particles. However, the viscosity value increased with the increasing amount of Gf as it was expected. The viscoelastic behavior of the microstructure at rest of the AVJ and Gf/AVJ suspensions was studied using oscillatory shear tests. First, linear viscoelastic response was confirmed in the relatively low amplitude shear region

(γ_{0} < 0.001)

using an amplitude sweep shear test. After that, frequency sweep shear tests were conducted in the region where Gf/AVJ suspensions showed linear viscoelastic behavior. Varying the frequency, the response of the microstructure at rest of the suspensions when the mechanical action lasts from short to long time interval can be characterized. Jeffreys mechanical model was used for the analysis of the LVE response of Gf/AVJ suspensions. Using small amplitude oscillatory shear (SAOS) tests, it was obtained that Gf/AVJ suspensions are viscoelastic liquids that change their texture from chewy to creamy when the Gf concentration increases. Full article

(This article belongs to the Special Issue Research on Rheology in Food Processing)

► Show Figures

Figure 1

12 pages, 835 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Evaluation of Bio-Oils in Terms of Fuel Properties

by Sławomir Stelmach, Karina Ignasiak, Agata Czardybon and Joanna Bigda

Processes 2023, 11(12), 3317; https://doi.org/10.3390/pr11123317 - 28 Nov 2023

Cited by 3 | Viewed by 3144

Abstract

In response to the global climate challenge and the increasing demand for energy, exploring renewable energy alternatives has become crucial. Bio-oils derived from biomass pyrolysis are emerging as potential replacements for fossil fuel-based liquid fuels. This paper shares findings from the Institute of [...] Read more.

In response to the global climate challenge and the increasing demand for energy, exploring renewable energy alternatives has become crucial. Bio-oils derived from biomass pyrolysis are emerging as potential replacements for fossil fuel-based liquid fuels. This paper shares findings from the Institute of Energy and Fuel Processing Technology on the quality of crude biomass pyrolysis bio-oil samples. These findings highlight their potential as motor liquid fuels. The article details the results of tests on the physicochemical properties of four distinct bio-oil samples. Additionally, it presents preliminary test results on the hydrodeoxygenation of bio-oils in a batch reactor. The production of homogeneous, stable mixtures using other fuel additives, such as diesel oil, rapeseed methyl ester (RME), and butanol, is also discussed. Full article

(This article belongs to the Special Issue Green Processes for Sustainable Fuel Production)

► Show Figures

Graphical abstract

26 pages, 81468 KiB

Open AccessEditor’s ChoiceArticle

Ultrasonic Vibration-assisted Electrochemical Discharge Machining of Quartz Wafer Micro-Hole Arrays

by Chun-Hao Yang, Tai-Ching Wang, Jung-Chou Hung and Hai-Ping Tsui

Processes 2023, 11(12), 3300; https://doi.org/10.3390/pr11123300 - 26 Nov 2023

Cited by 3 | Viewed by 1983

Abstract

The micro-hole machining of quartz wafers depends on photolithography techniques akin to those used in semiconductor fabrication. These methods present challenges due to high equipment setup costs, large space requirements, and environmental pollution risks. This research applies ultrasonic vibration assistance in electrochemical discharge [...] Read more.

The micro-hole machining of quartz wafers depends on photolithography techniques akin to those used in semiconductor fabrication. These methods present challenges due to high equipment setup costs, large space requirements, and environmental pollution risks. This research applies ultrasonic vibration assistance in electrochemical discharge machining to create an array of micro-holes on quartz wafers. In the experiments, a self-prepared tungsten carbide micro-electrode array served as the tool electrode. This electrode was a 2 × 2 square array, with needles measuring 30 × 30 μm. A series of experiments was conducted to investigate the effects of various machining parameters, including working voltage, feed rate, duration time, duty factor, and ultrasonic power level, on the characteristics of the micro-hole array. The characteristics included average hole diameter and through-hole surface morphology. The experimental objective was to achieve a through-hole diameter of 80 μm with an accuracy of ±8 μm. During the electrochemical discharge machining, suitable ultrasonic vibrations can thin the insulating gas film coating on the electrode surface, resulting in a more uniform gas film. As the insulating gas film’s thickness decreased, so did the critical voltage needed for the electrochemical discharge machining, reducing the hole’s diameter expansion. The ultrasonic vibration assistance can enable the satisfaction of the dimensional accuracy requirement. The experimental results indicate that ultrasonic vibration assistance can effectively improve the processing capacity and reduce sample fragmentation. A working voltage of 44 V, feed rate of 1 μm/6 s, duration time of 30 μs, duty factor of 30%, and ultrasonic power level of 1 resulted in better inlet and outlet surface morphology without outlet fragmentation. Moreover, the average diameters of the inlet and outlet were roughly 80 μm while meeting the through-hole diameter of 80 μm with accuracy of ±8 μm. Full article

(This article belongs to the Special Issue Low-Carbon Design and Manufacturing Processes)

► Show Figures

Figure 1

11 pages, 1317 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of Watermelon Seed Flour on the Physical, Chemical, and Sensory Properties of Low-Carbohydrate, High-Protein Bread

by Monika Wójcik, Agata Bieńczak, Paweł Woźniak and Renata Różyło

Processes 2023, 11(12), 3282; https://doi.org/10.3390/pr11123282 - 24 Nov 2023

Cited by 5 | Viewed by 3096

Abstract

Nowadays, many people struggle with various diseases, and to prevent this, a low-carbohydrate diet is recommended. Consumers are also looking for products with a high amount of plant proteins. This study investigated the preparation of low-carbohydrate and high-protein breads using flaxseed flour, buckwheat [...] Read more.

Nowadays, many people struggle with various diseases, and to prevent this, a low-carbohydrate diet is recommended. Consumers are also looking for products with a high amount of plant proteins. This study investigated the preparation of low-carbohydrate and high-protein breads using flaxseed flour, buckwheat flour, and pea protein enriched with watermelon seed flour at different contents (0, 5, 10, and 15%). The physical, chemical, and sensory properties of the bread were determined. Based on the research conducted, the loaves of bread with the addition of WSF had a higher volume compared to the control sample, but in the case of parameters of crumb color, no significant changes were observed (∆E < 5). Taking into account the sensory analysis, it is recommended to add 5% WSF to the base recipe; such bread meets the requirements for low-carbohydrate and high-protein food. The value of the amino acids (mg/g⁻¹) in the obtained bread was in the order of glutamic acid (64.9), followed by asparagine (37.3), arginine (32.6), lysine (20.4), serine (18.0), and alanine (17.0),higher than the corresponding value in the control bread. The findings suggested that the addition of WSF at a concentration of 5% could be used as a valuable functional ingredient to enhance the nutritive content of low-carbohydrate and high-protein bread, especially for the elderly and physically active people. Full article

(This article belongs to the Special Issue 10th Anniversary of Processes: Recent Advances in Food Processing Processes)

► Show Figures

Figure 1

21 pages, 7038 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Click Addition Reaction of Urethane–Acrylate Resin Using Octa(3-thiopropyl)silsesquioxane Derivatives as Cross-Linking Agents

by Daria Pakuła, Bogna Sztorch, Robert E. Przekop and Bogdan Marciniec

Processes 2023, 11(12), 3285; https://doi.org/10.3390/pr11123285 - 24 Nov 2023

Cited by 1 | Viewed by 1434

Abstract

In this work, new partially substituted derivatives of octa(3-thiopropyl)silsesquioxane (SSQ-8SH) were synthesized. The article compares the thiol-ene reaction using two methods: radical mechanism, thermally initiated (AIBN), and in the presence of a photoinitiator (DMPA). Both the crystalline and the oil forms of SSQ-8SH [...] Read more.

In this work, new partially substituted derivatives of octa(3-thiopropyl)silsesquioxane (SSQ-8SH) were synthesized. The article compares the thiol-ene reaction using two methods: radical mechanism, thermally initiated (AIBN), and in the presence of a photoinitiator (DMPA). Both the crystalline and the oil forms of SSQ-8SH were functionalized. Olefins with nonpolar alkyl groups (hexene, octene, and octadecene) and vinyltrimethoxysilane, allyl glycidyl ether, allyl 2,2,3,3,4,4,5,5-octafluoropentylether, allyl methacrylate, and styrene were used in the reactions, allowing to obtain seven new derivatives. All compounds were characterized using spectroscopic (¹H NMR and ²⁹Si NMR) and spectrometric (MALDI-TOF-MS) methods. The influence of functional groups on the water contact angle value was determined. The functionalization of the compound led to a contact angle value above 95° (SSQ-4SH-4OD). Density measurements and thermogravimetric analysis (TGA) were carried out for all compounds. The highest onset temperature (357.4 °C) and temperature at the maximum mass loss rate (377.3 °C) were observed for SSQ-SH-4OD. The addition of alkyl groups significantly decreased the density of compounds with increasing chain length (1.198 g/cm³; 1.162 g/cm³; 1.095 g/cm³ for hexene, octene, and octadecene, respectively). Silsesquioxanes have potential applications in various materials, such as UV-curable resins, allowing to modify, for example, their surface properties. Modification of a commercial photocurable resin with selected derivatives was carried out to determine the impact on physicochemical properties (TGA, WCA). Full article

(This article belongs to the Special Issue Technological Advancements in Nanomaterials Synthesis and Application)

► Show Figures

Figure 1

22 pages, 12813 KiB

Open AccessEditor’s ChoiceArticle

Oil Extraction and Natural Drying Kinetics of the Pulp and Seeds of Commercially Important Oleaginous Fruit from the Rainforests of Guyana

by Shaveshwar Deonarine, Navindra Soodoo, Laziz Bouzidi and Suresh S. Narine

Processes 2023, 11(12), 3292; https://doi.org/10.3390/pr11123292 - 24 Nov 2023

Cited by 3 | Viewed by 2163

Abstract

Ambient sun drying is the method most used by Indigenous communities for preserving fruits and seeds harvested from the forest. It is an effective method to increase the shelf-life of highly perishable foods and prevent spoilage until important bioactive compounds can be extracted [...] Read more.

Ambient sun drying is the method most used by Indigenous communities for preserving fruits and seeds harvested from the forest. It is an effective method to increase the shelf-life of highly perishable foods and prevent spoilage until important bioactive compounds can be extracted at distant locations. The ambient sun drying kinetics and oil extraction of the pulp and seeds of commercially important oleaginous fruit directly obtained from the rainforests and swamps of Guyana, namely Astrocaryum vulgare (Awara), Astrocaryum aculeatum (Kuru), Oenocarpus bacaba (Turu), Mauritia flexuosa (Ite), Euterpe oleracea (Acai), Caryocar nuciferum (Souari), Attalea maripa (Kukrit), and Carapa guianensis (Crabwood), were studied. The fruits were dried under ambient conditions from initial moisture contents ranging from 24–71% to a final moisture content of 5%. Three models, the Lewis model, the modified Page model, and the standard logistic function (SLF) model, were utilized to model the drying kinetics and to estimate the parameters governing the drying process. These models were demonstrated to fit the experimental data with excellent goodness of fit (>0.98). The SLF, never used before to model drying kinetics, was observed to be the best-suited model overall, with the highest correlation coefficient and the least Chi-square (χ²). Depending on the fruit type, the estimated point where the maximum drying rate occurs varies from 35 min to 350 min for sun-dried fruit pulp and up to 4000 min for sun-dried kernels. The steepness of the drying curves varied from −0.5 to −3.5 g/min. The results of this work will aid in the design, development, optimization, and control of the ambient drying processes of economically and functionally important oleaginous forest fruits. This knowledge will assist in addressing the key challenge of spoilage faced by Indigenous communities in the preservation of tropical oleaginous fruits and seeds, possibly aiding in the preservation of functional characteristics of the extracted oils and adducing to the sustainable economic utilization of such fruit. Full article

(This article belongs to the Special Issue Extraction, Characterization and Pharmacology of Natural Products (II))

► Show Figures

Graphical abstract

19 pages, 366 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review on Sweet Potato Syrup Production Process: Effective Parameters and Syrup Properties

by Kowsar Rezvanian, Shahryar Jafarinejad and Adelia C. Bovell-Benjamin

Processes 2023, 11(12), 3280; https://doi.org/10.3390/pr11123280 - 23 Nov 2023

Cited by 4 | Viewed by 4016

Abstract

Sweet potato is always considered a food item that gives a sufficient stock of calories, nutrients, and minerals, and its syrup has numerous applications in the food industry. There is a need to review sweet potato syrup production processes in order to develop [...] Read more.

Sweet potato is always considered a food item that gives a sufficient stock of calories, nutrients, and minerals, and its syrup has numerous applications in the food industry. There is a need to review sweet potato syrup production processes in order to develop cost-effective and reliable designs for its production. The overall objective of this study is to update the current knowledge of the sweet potato syrup production processes and factors affecting its production. This study briefly reviews the sweet potato (its varieties, cultivation, and chemical composition/nutritional values), syrup production processes (acidic hydrolysis, enzymatic hydrolysis, acid–enzyme hydrolysis, and other processes to improve the quality of syrup), and effective parameters (e.g., enzyme type, enzyme dosage, temperature, pH, the role of water, and the role of starch and starch pretreatment) on the syrup production process. Finally, based on the gaps identified in the area, it discusses the conclusions and future outlook. Full article

(This article belongs to the Special Issue Applications of Non-Thermal and Thermal Technologies in Food Processing)

21 pages, 8037 KiB

Open AccessEditor’s ChoiceArticle

Discrete Element Simulations of Contact Heat Transfer on a Batch-Operated Single Floor of a Multiple Hearth Furnace

by Nikoline Hilse, Max Kriegeskorte, Jonas Fischer, Phil Spatz, Enric Illana, Martin Schiemann and Viktor Scherer

Processes 2023, 11(12), 3257; https://doi.org/10.3390/pr11123257 - 21 Nov 2023

Cited by 1 | Viewed by 2096

Abstract

The multiple hearth furnace is a common industrial reactor for the thermal treatment of particulate material. The present contribution concentrates on a numerical analysis of contact heat transfer on a batch-operated single floor of a multiple hearth furnace employing the Discrete Element Method [...] Read more.

The multiple hearth furnace is a common industrial reactor for the thermal treatment of particulate material. The present contribution concentrates on a numerical analysis of contact heat transfer on a batch-operated single floor of a multiple hearth furnace employing the Discrete Element Method (DEM). The particles are agitated on an electrically heated circular floor by a single rotating rabble arm equipped with three flat blades. Blade angles have been varied from 0° to 90°. The DEM simulations (particle mechanics and contact heat transfer) were validated against experimental data. The transient heating of 20 mm diameter polyoxymethylene (POM) spheres was analysed. As the simulations did not consider natural convection inherently leading to time-varying heat losses, an averaged heat loss parameter was determined to represent heat dissipation from the particles to the surrounding gas and incorporated into the DEM simulations. With this approach, a good agreement with measurements was obtained. The DEM simulations and experiments do not show a large influence of the blade angle on the temporal evolution of the mean particle temperatures. However, the frequency distribution of particle temperature is dependent on the blade angle, revealing an increase in the standard deviation of the frequency distribution with an increasing blade angle. Full article

(This article belongs to the Section Particle Processes)

► Show Figures

Figure 1

16 pages, 7570 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Graphene Oxide from Graphite of Spent Batteries as Support of Nanocatalysts for Fuel Hydrogen Production

by Gabriel Sperandio, Iterlandes Machado Junior, Esteefany Bernardo and Renata Moreira

Processes 2023, 11(11), 3250; https://doi.org/10.3390/pr11113250 - 19 Nov 2023

Cited by 7 | Viewed by 2415

Abstract

The increasing production of electronic waste and the rising demand for renewable energy are currently subjects of debate. Sustainable processes based on a circular economy are required. Then, electronic devices could be the main source for the synthesis of new materials. Thus, this [...] Read more.

The increasing production of electronic waste and the rising demand for renewable energy are currently subjects of debate. Sustainable processes based on a circular economy are required. Then, electronic devices could be the main source for the synthesis of new materials. Thus, this work aimed to synthesize graphene oxide (GO) from graphite rod of spent Zn-C batteries. This was used as support for Ni/Co bimetallic nanocatalysts in the evolution of hydrogen from NaBH₄ for the first time. The graphene oxide (GO) exhibited a diffraction peak at 2θ = 9.1°, as observed using X-ray diffraction (XRD), along with the presence of oxygenated groups as identified using FTIR. Characteristic bands at 1345 and 1574 cm⁻¹ were observed using Raman spectroscopy. A leaf-shaped morphology was observed using SEM. GO sheets was observed using TEM, with an interplanar distance of 0.680 nm. Ni/Co nanoparticles, with an approximate size of 2 nm, were observed after deposition on GO. The material was used in the evolution of hydrogen from NaBH₄, obtaining an efficiency close to 90%, with a kinetic constant of 0.0230 s⁻¹ at 296.15 K and activation energy of 46.7 kJ mol⁻¹. The material showed an efficiency in seven reuse cycles. Therefore, a route of a new material with added value from electronic waste was obtained from an eco-friendly process, which can be used in NaBH₄ hydrolysis. Full article

(This article belongs to the Special Issue Wastewater and Waste Treatment: Overview, Challenges and Current Trends (Volume II))

► Show Figures

Figure 1

17 pages, 4884 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Exploration of Eco-Friendly Hydrochar’s Potential in Advanced Oxidative Processes for Dicamba Degradation within a Circular Bio-Economy Framework

by Tiago Guimarães, Elisa Maria Gomes da Silva, Adalin Cezar Moraes de Aguiar, Marcelo Moreira da Costa, Kamila Cabral Mielke, Kassio Ferreira Mendes, Antonio Alberto da Silva, Ana Paula de Carvalho Teixeira and Renata Pereira Lopes Moreira

Processes 2023, 11(11), 3244; https://doi.org/10.3390/pr11113244 - 17 Nov 2023

Cited by 3 | Viewed by 1482

Abstract

Dicamba, renowned for its limited sorption capacity, presents a substantial risk of contaminating surface and groundwater if the disposal of spray tank effluent is not adequately controlled. In this work, a dicamba effluent underwent treatment through a Fenton-like process employing an iron/hydrochar (Hy-Fe) [...] Read more.

Dicamba, renowned for its limited sorption capacity, presents a substantial risk of contaminating surface and groundwater if the disposal of spray tank effluent is not adequately controlled. In this work, a dicamba effluent underwent treatment through a Fenton-like process employing an iron/hydrochar (Hy-Fe) composite, synthesized via hydrothermal methods using coffee husk as the precursor. The Hy-Fe displayed carbon, hydrogen, and nitrogen levels of 52.30%, 5.21%, and 1.49%, respectively. Additionally, the material exhibited a specific surface area measuring 9.00 m² g⁻¹. The presence of the γ-Fe₂O₃ phase within the composite was confirmed through X-ray diffraction analysis. The Fenton-like process employing Hy-Fe demonstrated approximately 100% degradation of dicamba within 5 h. The treated effluent underwent toxicity evaluation via biological assays using beans (Phaseolus vulgaris) as indicator plants, revealing no observable signs of intoxication. These findings were corroborated by High-Performance Liquid Chromatography, providing additional confirmation of the degradation results. Additionally, decontamination of personal protective equipment potentially contaminated with dicamba was also assessed. The Hy-Fe composite demonstrated reusability across three degradation cycles, achieving degradation percentages of 100%, 70%, and 60%, respectively. The Hy-Fe composite demonstrates substantial potential for use in a Fenton-like process. This process is characterized by its simplicity, speed, and sustainability. The notable effectiveness, evidenced by high degradation rates and minimal toxicity, underscores its suitability as a practical solution for addressing dicamba contamination. Full article

(This article belongs to the Special Issue Application of Environmentally Friendly Technologies in Green Processes)

► Show Figures

Graphical abstract

16 pages, 3485 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Aspergillus fumigatus Lytic Polysaccharide Monooxygenase AfLPMO9D: Biochemical Properties and Photoactivation of a Multi-Domain AA9 Enzyme

by Pedro Ricardo Vieira Hamann, Milena Moreira Vacilotto, Fernando Segato and Igor Polikarpov

Processes 2023, 11(11), 3230; https://doi.org/10.3390/pr11113230 - 16 Nov 2023

Viewed by 1428

Abstract

Lytic polysaccharide monooxygenases (LPMOs) are critical players in enzymatic deconstruction of cellulose. A number of LPMOs have been identified at a genomics level; however, they still need to be characterized and validated for use in industrial processes aimed at cellulose deconstruction. In the [...] Read more.

Lytic polysaccharide monooxygenases (LPMOs) are critical players in enzymatic deconstruction of cellulose. A number of LPMOs have been identified at a genomics level; however, they still need to be characterized and validated for use in industrial processes aimed at cellulose deconstruction. In the present study, we biochemically characterized a new LPMO, a member of auxiliary activities family 9 (AA9) from the filamentous fungus Aspergillus fumigatus (AfLPMO9D). This LPMO demonstrated higher efficiency against amorphous cellulose as compared to more recalcitrant forms of cellulose such as bacterial cellulose and Avicel. AfLPMO9D has a capacity to oxidize the substrate at either the C₁ or C₄ positions, with pH-dependent regioselectivity. Photoactivation experiments demonstrated that light-stimulated chlorophyllin triggers AfLPMO9D activation without requirements of an external electron donor. AfLPMO9D is capable of boosting phosphoric acid-swollen cellulose depolymerization via GH7 endoglucanase and cellobiohydrolase. The results of the present study might help to elucidate the role of different LPMOs in cellulosic fiber deconstruction. Full article

(This article belongs to the Section Biological Processes and Systems)

► Show Figures

Graphical abstract

22 pages, 8979 KiB

Open AccessEditor’s ChoiceArticle

3D Printed, Single-Use Bioreactor with Integrated Inline Sensors for Microbial and Mammalian Cell Cultivation—A Case Study

by Samuel Lukas Schneider, Stefan Seidel, Andressa Seefeldt, Michael Romang, Simon Kastl, Julia Gensel, Thomas Neumeyer, Gernot Thomas John and Dieter Eibl

Processes 2023, 11(11), 3231; https://doi.org/10.3390/pr11113231 - 16 Nov 2023

Viewed by 3471

Abstract

The development of upstream bioprocesses necessitates small, instrumented bioreactors for investigating and optimizing production processes in a cost-effective manner. Due to advances in both the equipment and the materials used in additive manufacturing, 3D printing of customized bioreactors is now in the realm [...] Read more.

The development of upstream bioprocesses necessitates small, instrumented bioreactors for investigating and optimizing production processes in a cost-effective manner. Due to advances in both the equipment and the materials used in additive manufacturing, 3D printing of customized bioreactors is now in the realm of possibilities. In this study, a small-scale 3D printed bioreactor suitable for mammalian and microbial cultivations was developed, featuring a working volume of 90 mL, inline pH and dissolved oxygen probes and a levitating magnetic stirrer. Aeration channels and a sampling port were printed directly into the vessel walls. Additionally, the vessel was equipped with a 3D printed customizable optical biomass-sensor. The bioreactor’s performance was evaluated through technical characterization and proof of concept cultivations, demonstrating that mixing time and oxygen mass transfer were sufficient for cultivating mammalian as well as microbial cells at high cell densities. Specifically, an Escherichia coli fed-batch cultivation achieved a maximum OD₆₀₀ of 204. Furthermore, a fed-batch cultivation of an IgG antibody-producing Chinese hamster ovary cell line reached a peak viable cell density of 10.2 × 10⁶ cells mL⁻¹ and a maximum product titer of 2.75 g L⁻¹. Using a three-parameter fit, the inline biomass signal could be correlated to the corresponding offline values with satisfactory accuracy, making it possible to monitor cell growth in real-time. Full article

(This article belongs to the Section Pharmaceutical Processes)

► Show Figures

Figure 1

12 pages, 4817 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effects of MgO and Rare-Earth Oxides (Y₂O₃, Yb₂O₃, Dy₂O₃) on the Structural Characteristics and Electrical Properties of BaTiO₃

by Jae Hoon Park and Eung Soo Kim

Processes 2023, 11(11), 3235; https://doi.org/10.3390/pr11113235 - 16 Nov 2023

Cited by 3 | Viewed by 1649

Abstract

This study investigated the impact of MgO and rare-earth oxides (Y₂O₃, Yb₂O₃, and Dy₂O₃) on the structural characteristics and electrical properties of BaTiO₃. Specimens sintered at 1350 °C for [...] Read more.

This study investigated the impact of MgO and rare-earth oxides (Y₂O₃, Yb₂O₃, and Dy₂O₃) on the structural characteristics and electrical properties of BaTiO₃. Specimens sintered at 1350 °C for durations ranging from 1 to 5 h in air exhibited a single phase of BaTiO₃ with a tetragonal structure. This was observed for pure BaTiO₃ and specimens co-doped with MgO-Y₂O₃ and/or MgO-Dy₂O₃. However, a pseudo-cubic structure of BaTiO₃ was detected for specimens doped with MgO or co-doped with MgO-Yb₂O₃. The unit-cell volume of the sintered specimens was found to be dependent on the type of substitution ion for the A/B site of BaTiO₃ (ABO₃). The dielectric constant (ε_r) of the sintered specimens decreased with the substitution of MgO and rare-earth oxides due to a decrease in tetragonality (c/a). The electrical resistivities of the sintered specimens were influenced not only by their microstructural characteristics but also by the secondary phases of the sintered specimens. The BaTiO₃ specimens co-doped with MgO-Yb₂O₃ and/or doped with MgO met the EIA X7R and X8R specifications (−55 to 125~150 °C, ΔC/C = ±15% or less), respectively. Full article

(This article belongs to the Special Issue Advances in Ceramic Processing and Application of Ceramic Materials)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI