Processes

14 pages, 1120 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of Different Dehydration Methods on Drying Efficiency, Nutritional and Physico-Chemical Quality of Strawberries Slices (Fragaria ananassa)

by Patrícia Antunes, Sara Dias, Diogo Gonçalves, Telma Orvalho, Marta B. Evangelista, Enrique Pino-Hernández and Marco Alves

Processes 2025, 13(7), 2065; https://doi.org/10.3390/pr13072065 - 30 Jun 2025

Viewed by 456

Abstract

This study aimed to evaluate the drying kinetics, microstructural features, moisture content, color, pH, aw, texture, acidity, rehydration capacity, and sensorial attributes of strawberry slices processed by different drying methodologies. Strawberry samples were processed by hot air-drying (HA, 60 °C, 0.5 m/s), freeze-drying [...] Read more.

This study aimed to evaluate the drying kinetics, microstructural features, moisture content, color, pH, aw, texture, acidity, rehydration capacity, and sensorial attributes of strawberry slices processed by different drying methodologies. Strawberry samples were processed by hot air-drying (HA, 60 °C, 0.5 m/s), freeze-drying (FD, 0.055 mbar), and pulsed electric field (PEF)-assisted freeze-drying (PEFFD, 1 kV/cm and 3.2 kJ/kg). PEF pre-treatment significantly increased cell membrane permeability by forming micropores, which led to a significant reduction in the moisture content of up to 8.87% and improved the drying efficiency. Nonetheless, this pre-treatment did not significantly alter the drying rate due to the inherent constraints of the freeze-drying process. PEFFD samples better retained their shape, volume, and visual quality, and exhibited a maximum rehydration capacity of 64.90%. The ascorbic acid retention was found to be higher in the FD and PEFFD when compared to HA. FD and PEFFD samples had an increase in both red and yellow hue. PEF shows promise as a pre-treatment technique, improving both the drying efficiency and strawberry quality. Further studies are needed to assess PEFFD’s industrial scalability and economic feasibility. Full article

(This article belongs to the Special Issue Emerging Thermal and Non-Thermal Technologies for Food Preservation and Sustainable Food Processing)

► Show Figures

Figure 1

16 pages, 2460 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Experimental Study on the Influence of Magnesium on the Separation of Carbon Dioxide from Gas Mixtures with Nitrogen by Combustion Processes

by Ioan Barabulica, Marius Sebastian Secula, Eugenia Teodora Iacob-Tudose and Ioan Mamaliga

Processes 2025, 13(7), 2054; https://doi.org/10.3390/pr13072054 - 28 Jun 2025

Viewed by 364

Abstract

The goal of this paper consists in the experimental evaluation of the possibility to separate industrial gases using magnesium combustion in carbon dioxide–nitrogen mixtures of various concentrations. The choice was made primarily due to the chemical inertness of these two gases. The study [...] Read more.

The goal of this paper consists in the experimental evaluation of the possibility to separate industrial gases using magnesium combustion in carbon dioxide–nitrogen mixtures of various concentrations. The choice was made primarily due to the chemical inertness of these two gases. The study investigates how the Mg combustion changes the concentration of the initial gas mixture and the possibility to apply this process to separate this gas mixture. On the other hand, due to its greenhouse effect, CO₂ separation is a process of high interest in itself. Mg reacts exothermically with CO₂, so a potential use for this purpose will also benefit from a significant amount of recovered thermal energy. N₂ has a particular importance due to its potential to be purified using Mg combustion, and this application might be an economical alternative to air distillation, which is widely used for N₂ production at industrial scale. In practice, the CO₂-N₂ mixtures are commonly used as flue gases resulting from various combustion systems. Mg combustion residue is analyzed by means of energy-dispersive X-ray spectroscopy. It is found that Mg can substantially reduce the concentration of CO₂, even more than the stoichiometric reaction for the formation of MgO would suggest. The percentage decrease in CO₂ concentration reaches values over 10 vol.%. A secondary yet notable effect is the heat generated by the Mg and CO₂ reaction, which is currently being studied as an energy source alternative. Full article

(This article belongs to the Special Issue Experimental and Numerical Study of Flame Propagation of Biofuels/Oxidizers/Inert Mixtures (Volume II))

► Show Figures

Figure 1

45 pages, 11750 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Progress and Challenges in Microbial Defluorination and Degradation for Sustainable Remediation of Fluorinated Xenobiotics

by Mohd Faheem Khan

Processes 2025, 13(7), 2017; https://doi.org/10.3390/pr13072017 - 25 Jun 2025

Viewed by 1529

Abstract

Fluorinated xenobiotics, such as per- and polyfluoroalkyl substances (PFAS), fluorinated pesticides, and pharmaceuticals, are extensively used across industries, but their extreme persistence, driven by the high carbon–fluorine (C–F) bond dissociation energy (~485 kJ/mol), poses serious environmental and health risks. These compounds have been [...] Read more.

Fluorinated xenobiotics, such as per- and polyfluoroalkyl substances (PFAS), fluorinated pesticides, and pharmaceuticals, are extensively used across industries, but their extreme persistence, driven by the high carbon–fluorine (C–F) bond dissociation energy (~485 kJ/mol), poses serious environmental and health risks. These compounds have been detected in water, soil, and biota at concentrations from ng/L to µg/L, leading to widespread contamination and bioaccumulation. Traditional remediation approaches are often costly (e.g., EUR >100/m³ for advanced oxidation), energy-intensive, and rarely achieve complete degradation. In contrast, microbial defluorination offers a low-energy, sustainable alternative that functions under mild conditions. Microorganisms cleave C–F bonds through reductive, hydrolytic, and oxidative pathways, mediated by enzymatic and non-enzymatic mechanisms. Factors including electron donor availability and oxygen levels critically influence microbial defluorination efficiency. Microbial taxa, including bacteria, fungi, algae, and syntrophic consortia, exhibit varying defluorination capabilities. Metagenomic and microbial ecology studies continue to reveal novel defluorinating organisms and metabolic pathways. Key enzymes, such as fluoroacetate dehalogenases, cytochrome P450 monooxygenases, reductive dehalogenases, peroxidases, and laccases, have been characterised, with structural and mechanistic insights enhancing the understanding of their catalytic functions. Enzyme engineering and synthetic biology tools now enable the optimisation of these enzymes, and the design of microbial systems tailored for fluorinated compound degradation. Despite these advances, challenges remain in improving enzyme efficiency, broadening substrate specificity, and overcoming physiological constraints. This review emphasises the emerging promise of microbial defluorination as a transformative and green solution, uniquely integrating recent multidisciplinary findings to accelerate the development of sustainable microbial defluorination strategies for effective remediation of fluorinated xenobiotics. Full article

(This article belongs to the Special Issue 1st SUSTENS Meeting: Advances in Sustainable Engineering Systems)

► Show Figures

Figure 1

57 pages, 3664 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advancing Municipal Solid Waste Management Through Gasification Technology

by Uzeru Haruna Kun and Ewelina Ksepko

Processes 2025, 13(7), 2000; https://doi.org/10.3390/pr13072000 - 24 Jun 2025

Cited by 1 | Viewed by 1085

Abstract

This review thoroughly evaluates gasification as a transformative alternative to conventional methods for managing municipal solid waste (MSW), highlighting its potential to convert carbonaceous materials into syngas for energy and chemical synthesis. A comparative evaluation of more than 350 papers and documents demonstrated [...] Read more.

This review thoroughly evaluates gasification as a transformative alternative to conventional methods for managing municipal solid waste (MSW), highlighting its potential to convert carbonaceous materials into syngas for energy and chemical synthesis. A comparative evaluation of more than 350 papers and documents demonstrated that gasification is superior to incineration and pyrolysis, resulting in lower harmful emissions and improved energy efficiency, which aligns with sustainability goals. Key operational findings indicate that adjusting the temperature to 800–900 °C leads to the consumption of CO₂ and the production of CO via the Boudouard reaction. Air gasification produces syngas yields of up to 76.99 wt% at 703 °C, while oxygen gasification demonstrates a carbon conversion efficiency of 80.2%. Steam and CO₂ gasification prove to be effective for producing H₂ and CO, respectively. Catalysts, especially nickel-based ones, are effective in reducing tar and enhancing syngas quality. Innovative approaches, such as co-gasification, plasma and solar-assisted gasification, chemical looping, and integration with carbon capture, artificial intelligence (AI), and the Internet of Things (IoT), show promise in improving process performance and reducing technical and economic hurdles. The review identifies research gaps in catalyst development, feedstock variability, and system integration, emphasizing the need for integrated research, policy, and investment to fully realize the potential of gasification in the clean energy transition and sustainable MSW management. Full article

(This article belongs to the Special Issue Advances in Solid Waste Treatment and Design (2nd Edition))

► Show Figures

Figure 1

15 pages, 1518 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Machine Learning-Based Prediction of Scale Inhibitor Efficiency in Oilfield Operations

by Seyed Hossein Hashemi and Farshid Torabi

Processes 2025, 13(7), 1964; https://doi.org/10.3390/pr13071964 - 21 Jun 2025

Cited by 1 | Viewed by 449

Abstract

Water injection is widely recognized as one of the most important operational approaches for enhanced oil recovery in oilfields. However, this process faces significant challenges due to the formation of sulfate and carbonate mineral scales caused by high salinity in both injected water [...] Read more.

Water injection is widely recognized as one of the most important operational approaches for enhanced oil recovery in oilfields. However, this process faces significant challenges due to the formation of sulfate and carbonate mineral scales caused by high salinity in both injected water and formation water. To address this issue, the use of mineral scale inhibitors has emerged as a valuable solution. In this study, we evaluated the performance of seven machine learning algorithms (Gradient Boosting Machine; k-Nearest Neighbors; Decision Tree; Random Forest; Linear Regression; Neural Network; and Gaussian Process Regression) to predict inhibitor efficiency. The models were trained on a comprehensive dataset of 661 samples (432 for training; 229 for testing) with 66 features including temperature; concentrations of various ions (sodium; calcium, magnesium; barium; strontium; chloride; sulfate; bicarbonate; carbonate, etc.), and inhibitor dosage levels (DTPMP, PPCA, PBTC, EDTMP, BTCA, etc.). The results showed that GPR achieved the highest prediction accuracy with R² = 0.9608, followed by Neural Network (R² = 0.9230) and Random Forest (R² = 0.8822). These findings demonstrate the potential of machine learning approaches for optimizing scale inhibitor performance in oilfield operations Full article

(This article belongs to the Special Issue Recent Advances in Heavy Oil Reservoir Simulation and Fluid Dynamics)

► Show Figures

Figure 1

14 pages, 2714 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

5-Fluorouracil Encapsulation in PLA Films: The Role of Chitosan Particles in Modulating Drug Release and Film Properties

by Sofia Milenkova and Maria Marudova

Processes 2025, 13(7), 1961; https://doi.org/10.3390/pr13071961 - 21 Jun 2025

Viewed by 2385

Abstract

The development of effective drug delivery systems, in terms of their application route and release profile, is crucial for improving the therapeutic outcomes of all bioactive compounds. In this study, we explored the encapsulation of 5-fluorouracil, a commonly used chemotherapeutic agent, in poly(lactic [...] Read more.

The development of effective drug delivery systems, in terms of their application route and release profile, is crucial for improving the therapeutic outcomes of all bioactive compounds. In this study, we explored the encapsulation of 5-fluorouracil, a commonly used chemotherapeutic agent, in poly(lactic acid) films for the first time and the role of chitosan particles in the structure, as no previous studies have examined their potential for this purpose. The objective is to enhance the sustained release of 5-FU and minimise the burst release step while leveraging the biocompatibility and biodegradability of these polymers. PLA films were fabricated using a solvent casting method, and 5-FU was encapsulated either directly within the PLA matrix or loaded into chitosan particles, which were then incorporated into the film. The physicochemical properties of the films, including morphology, wettability, phase state of the drug, thermal stability, drug loading efficiency, and release kinetics, were evaluated along with their barrier and mechanical properties. The results indicate a change in morphology after the addition of the drug and/or particles compared to the empty film. Additionally, the strain value at break decreased from nearly 400% to below 15%. Young’s modulus also changes from 292 MPa to above 500 MPa. The addition of chitosan particles lowered the permeability and vapour transmission rate slightly, while dissolving 5-FU increased them to 241 g/m²·24 h and 1.56 × 10⁻¹³ g·mm/m²·24 h·kPa, respectively. Contact angle and surface energy values went from 71° and 34 mJ/m² for pure PLA to below 53° and around 58 mJ/m² for the composite structures, respectively. Drug release tests, conducted for 8 h, indicated a nearly 2-fold decrease in the amount of drug released from the film with particles within this period, from around 45% for bare particles and PLA film to 25% for the combined structure, indicating the potential of this system for sustained release of 5-FU. Full article

(This article belongs to the Special Issue Development and Characterization of Advanced Polymer Nanocomposites)

► Show Figures

Graphical abstract

15 pages, 7178 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Octagonal Starfish-Inspired Roller Imprinting Control for Multi-Space and Multi-Axial Microstructure Replication

by Yung-Jin Weng, Yi-Xuan Zhong, Jin-Chen Guo and Zi-Jia Wang

Processes 2025, 13(7), 1966; https://doi.org/10.3390/pr13071966 - 21 Jun 2025

Viewed by 2469

Abstract

This study proposes a novel octagonal starfish-inspired roller imprinting control for multi-space and multi-axial microstructure replication, featuring a roller printing system with a controllable mold structure for multi-space and multi-axis applications. First, a microstructure was made and a micro mold was replicated to [...] Read more.

This study proposes a novel octagonal starfish-inspired roller imprinting control for multi-space and multi-axial microstructure replication, featuring a roller printing system with a controllable mold structure for multi-space and multi-axis applications. First, a microstructure was made and a micro mold was replicated to develop and simulate a negative Poisson ratio structure as a special structure to control the polymer microstructure mold. Meanwhile, a spatial axial roller imprinting system was designed as a roller imprinting replication system for the replication and roller imprinting of microstructures to research and conduct a roller imprinting testing experiment. The experiment results showed that the multi-space and multi-axial roll imprinting processing system with a controllable mold in this research had high replication formability. The results proved that the high replication formability of the microstructure obtained through white light scanning after subsequent roller imprinting was up to 98.75%. The diameter of the microstructure reached 99.025%, and the development of this innovative system and method of new technology could obtain the expected replication formability of the microstructure. Meanwhile, good achievements were obtained through optical preliminary validation. The results of this research could provide a reference about continuous microstructure component roll forming processing for academic and technological development. Full article

(This article belongs to the Special Issue Numerical Simulation and Heat Transfer in Material Processing and Casting Engineering)

► Show Figures

Figure 1

33 pages, 1913 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Sulfate Radical-Based Oxidation Processes for Emerging Contaminants: Advances and Perspectives on Degradation of Hormones

by Camila S. S. Tolêdo, Daniele M. Bila and Juacyara C. Campos

Processes 2025, 13(7), 1949; https://doi.org/10.3390/pr13071949 - 20 Jun 2025

Viewed by 583

Abstract

The increasing presence of emerging contaminants in aquatic environments, particularly endocrine disruptors (EDs), has raised significant environmental and public health concerns due to their toxicity, persistence, and ability to interfere with the endocrine systems of both aquatic organisms and humans. Among these compounds, [...] Read more.

The increasing presence of emerging contaminants in aquatic environments, particularly endocrine disruptors (EDs), has raised significant environmental and public health concerns due to their toxicity, persistence, and ability to interfere with the endocrine systems of both aquatic organisms and humans. Among these compounds, the steroid hormones 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) stand out, as they are frequently detected in wastewater, even after conventional treatment processes, which often exhibit limited removal efficiency. In this context, advanced oxidation processes (AOPs), especially those based on the generation of sulfate radicals (SO₄•⁻), have emerged as promising alternatives due to their high redox potential, extended half-life, and broad effectiveness across various pH levels. This work reviews recent advances in AOPs for the degradation of E2 and EE2, focusing on sulfate radical-based processes. The main degradation mechanisms, operational parameters, removal efficiency, challenges for large-scale application, and gaps in the current literature are discussed. The analysis indicates that despite their high effectiveness, sulfate radical-based processes still require further investigation in real wastewater matrices, the assessment of the toxicity of by-products, and the optimization of operational variables to be established as viable and sustainable technologies for wastewater treatment. Full article

(This article belongs to the Special Issue Advanced Oxidation Processes for Water and Wastewater Treatment: Developments, Challenges, and Opportunities)

► Show Figures

Graphical abstract

13 pages, 4110 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Development of a Hybrid Heat Exchange Air Conditioner with a Ground Heat Exchanger Placed Downstream from the Outdoor Unit Heat Exchanger

by Shumpei Funatani, Yusaku Tsukamoto and Koji Toriyama

Processes 2025, 13(6), 1925; https://doi.org/10.3390/pr13061925 - 18 Jun 2025

Viewed by 1192

Abstract

This study presents an innovative hybrid geothermal air conditioning system that combines conventional air-based heat exchange with ground heat exchange technology. The system features a ground heat exchanger placed downstream from the outdoor unit heat exchanger, requiring minimal modifications to conventional air conditioners [...] Read more.

This study presents an innovative hybrid geothermal air conditioning system that combines conventional air-based heat exchange with ground heat exchange technology. The system features a ground heat exchanger placed downstream from the outdoor unit heat exchanger, requiring minimal modifications to conventional air conditioners through the addition of bypass flow paths and a four-way valve. This design ensures that the ground heat exchanger consistently operates after the outdoor unit heat exchanger in both cooling and heating modes. The researchers evaluated the proposed system’s performance through both computational simulation (1D-CAE) and experimental testing. Simulation results demonstrated significant efficiency improvements, with the hybrid system achieving a coefficient of performance (COP) of 4.51 compared to just 1.24 for conventional air conditioners under extreme temperature conditions (38 °C). The experimental validation with a shallow-buried (20 cm) ground heat exchanger confirmed an approximately 20% COP improvement across various ambient temperatures. The main advantages of this hybrid system over conventional geothermal systems include reduced installation costs due to shorter borehole lengths, separate air conditioning units and underground piping, and compatibility with existing control systems. The design addresses skilled labor shortages while enabling large-scale demonstration operations with minimal initial investment. Future work will focus on optimizing the burial depth and conducting long-term durability testing to advance practical implementation. Full article

(This article belongs to the Special Issue Energy Storage Systems and Thermal Management)

► Show Figures

Figure 1

14 pages, 4310 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Different Gelling Agents on the Properties of Wine Jellies Prepared from Aromatic Grape Varieties

by Radek Sotolář, Petr Bača, Vladimír Mašán, Petr Vanýsek, Patrik Burg, Tomáš Binar and Oldřiška Sotolářová

Processes 2025, 13(6), 1893; https://doi.org/10.3390/pr13061893 - 15 Jun 2025

Viewed by 482

Abstract

Wine jelly is regarded as a delicacy in many countries and is commonly utilized in grande cuisine. Recently, its popularity has increased among consumers due to its dietary properties and the presence of health-promoting compounds such as antioxidants. Its natural origin and the [...] Read more.

Wine jelly is regarded as a delicacy in many countries and is commonly utilized in grande cuisine. Recently, its popularity has increased among consumers due to its dietary properties and the presence of health-promoting compounds such as antioxidants. Its natural origin and the ability to reflect local traditions and consumer preferences further enhance its appeal. This study aimed to compare the compositional and sensory characteristics of wine jellies prepared using three different gelling agents and four aromatic grape varieties, with the goal of preserving varietal aroma in the final products. White wines from Pálava and Moravian Muscat and red wines from Agni and Rosa were used. The selected gelling agents were agar, vegan gelatin, and traditional gelatin. Basic analytical parameters were assessed in both the wines and the resulting jellies. Sensory evaluation was conducted by trained panelists, assessing consistency, appearance (clarity), taste, and bouquet. Confectionery-grade jelly from red wines demonstrated the best consistency, while gelatin jellies from white wines showed superior clarity. Due to a preference for sweeter flavors, jellies from red wines were favored across all variants. The strongest varietal bouquet was observed in Moravian Muscat samples, irrespective of the gelling agent used. The optimal choice of gelling agent depends on the target quality attributes. Gelatin is preferred for firmness and clarity, while vegan gelatin is ideal for preserving aroma and achieving a balanced sensory profile. Full article

(This article belongs to the Special Issue Advances in Production, Processing and Analysis of Must, Wine and Derivatives)

► Show Figures

Figure 1

32 pages, 7243 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Artificial Intelligence and Extraction of Bioactive Compounds: The Case of Rosemary and Pressurized Liquid Extraction

by Martha Mantiniotou, Vassilis Athanasiadis, Konstantinos G. Liakos, Eleni Bozinou and Stavros I. Lalas

Processes 2025, 13(6), 1879; https://doi.org/10.3390/pr13061879 - 13 Jun 2025

Cited by 1 | Viewed by 508

Abstract

Rosemary (Rosmarinus officinalis or Salvia rosmarinus) is an aromatic herb that possesses numerous health-promoting and antioxidant properties. Pressurized Liquid Extraction (PLE) is an efficient, environmentally friendly technique for obtaining valuable compounds from natural sources. The optimal PLE conditions were established as [...] Read more.

Rosemary (Rosmarinus officinalis or Salvia rosmarinus) is an aromatic herb that possesses numerous health-promoting and antioxidant properties. Pressurized Liquid Extraction (PLE) is an efficient, environmentally friendly technique for obtaining valuable compounds from natural sources. The optimal PLE conditions were established as 25% v/v ethanol at 160 °C for 25 min, and a liquid-to-solid ratio of 10 mL/g. The optimal extract exhibited high polyphenol and antioxidant content through various assays. The recovered bioactive compounds possess potential applications in the food, pharmaceutical, and cosmetics sectors, in addition to serving as feed additives. This research compares two distinct optimization models: one statistical, derived from experimental data, and the other based on artificial intelligence (AI). The objective was to evaluate if AI could replicate experimental models and ultimately supplant the laborious experimental process, yielding the same results more rapidly and adaptably. To further enhance data interpretation and predictive capabilities, six machine learning models were implemented on the original dataset. Due to the limited sample size, synthetic data were generated using Random Forest (RF)-based resampling and Gaussian noise addition. The augmented dataset significantly improved the model performance. Among the models tested, the RF algorithm achieved the highest accuracy. Full article

(This article belongs to the Special Issue Application of Artificial Intelligence in Industrial Process Modelling and Optimization)

► Show Figures

Figure 1

21 pages, 1805 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Quality, Nutritional Composition, and Antioxidant Potential of Muffins Enriched with Flax Cake

by Dorota Gumul, Marek Kruczek, Katarzyna Szary-Sworst, Renata Sabat and Anna Wywrocka-Gurgul

Processes 2025, 13(6), 1875; https://doi.org/10.3390/pr13061875 - 13 Jun 2025

Viewed by 503

Abstract

The aim of this study was to investigate the im pact of incorporating flaxseed cake into wheat muffins on the levels of selected nutritional and bioactive compounds, specifically total polyphenols, phenolic acids, flavonols, and flavonoids. The influence of different levels of this additive [...] Read more.

The aim of this study was to investigate the im pact of incorporating flaxseed cake into wheat muffins on the levels of selected nutritional and bioactive compounds, specifically total polyphenols, phenolic acids, flavonols, and flavonoids. The influence of different levels of this additive on the quality attributes of the final product—such as color, texture, and volume—was also assessed. Furthermore, the health-promoting potential of the enriched muffins was analyzed using two free radical scavenging methods (DPPH and ABTS). The findings demonstrated that incorporating flax cake significantly increased the content of polyphenols and flavonoids (up to threefold) and phenolic acids (up to fortyfold). This highlights the potential of using flax cake to enrich food products and enhance the bioactive compound content of wheat muffins. Higher levels of flax cake addition (20%, 30%, and 40%) resulted in a notable increase in antioxidant activity, thereby enhancing the health-promoting properties of the muffins. Muffins with a 10% addition of flax cake exhibited comparable volume and reduced hardness relative to the control and a pleasant color. Full article

(This article belongs to the Special Issue Food Biochemistry and Health: Recent Developments and Perspectives)

► Show Figures

Graphical abstract

21 pages, 3275 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Biochar as a Catalyst in Persulfate Activation: A Sustainable Approach to Remove Pesticides from Water

by Tajana Simetić, Tijana Marjanović Srebro, Tamara Apostolović, Jasmina Anojčić, Nina Đukanović, Sanja Mutić, Jelena Molnar Jazić and Jelena Beljin

Processes 2025, 13(6), 1856; https://doi.org/10.3390/pr13061856 - 12 Jun 2025

Viewed by 625

Abstract

This study explores biochar-based catalysts made from hardwood (HW) and wheat straw (WS) biomass for activating persulfate (PS) in the removal of lindane and β-endosulfan from water. The effects of pyrolysis temperature, solution pH, and PS concentration were investigated. The results indicated that [...] Read more.

This study explores biochar-based catalysts made from hardwood (HW) and wheat straw (WS) biomass for activating persulfate (PS) in the removal of lindane and β-endosulfan from water. The effects of pyrolysis temperature, solution pH, and PS concentration were investigated. The results indicated that both feedstock and pyrolysis temperature are key factors influencing biochar composition. Biochars pyrolyzed at 700 °C exhibited higher surface areas compared to those pyrolyzed at 400 °C, suggesting more effective interactions with the target pesticides. Changes in pH had a minimal impact on pesticide removal, while increasing the PS concentration from 0.5 to 3 mM accelerated degradation. However, further increases in PS concentration slowed the degradation of both pesticides. Under optimal conditions (pH of 7.0 ± 0.2 and PS concentration of 3 mM), the HW700/PS and WS700/PS systems achieved > 90% removal of pesticides within 4 h. Quenching experiments confirmed that non-radical species (¹O₂), generated through persulfate activation by biochar, were the key factor in lindane degradation in both systems, supporting the catalytic role of biochar rather than mere adsorption. In the HW700/PS system, SO₄^•−, HO^•, and ¹O₂ acted synergistically to enhance the degradation of β-endosulfan, whereas in the WS700/PS system, the degradation was mainly driven by SO₄^•− and ¹O₂. Notably, HW700 biochar maintained its activation efficiency during β-endosulfan degradation even after five cycles. This research offers new insights into the potential of biochar-activated PS as a green, cost-effective, and efficient method for water treatment, addressing pesticide-contaminated surface water and promoting agricultural waste recycling. Full article

(This article belongs to the Special Issue Application of Biochar in Environmental Research)

► Show Figures

Figure 1

19 pages, 3279 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Data-Driven Prediction of Crystal Size Metrics Using LSTM Networks and In Situ Microscopy in Seeded Cooling Crystallization

by Ivan Vrban, Nenad Bolf and Josip Budimir Sacher

Processes 2025, 13(6), 1860; https://doi.org/10.3390/pr13061860 - 12 Jun 2025

Viewed by 559

Abstract

This work presents a data-driven modeling framework for predicting image-derived crystal size metrics in seeded cooling crystallization using Long Short-Term Memory (LSTM) neural networks. The model leverages in situ microscopy data to predict square-weighted D10, D50, D90, and particle counts based solely on [...] Read more.

This work presents a data-driven modeling framework for predicting image-derived crystal size metrics in seeded cooling crystallization using Long Short-Term Memory (LSTM) neural networks. The model leverages in situ microscopy data to predict square-weighted D10, D50, D90, and particle counts based solely on seed loading and temperature profiles, without requiring real-time supersaturation measurements. To enhance predictive power, engineered process descriptors—including temperature derivatives and integrals—were incorporated as dynamic features. Experimental validation was performed using creatine monohydrate crystallization from aqueous solution, with LSTM models trained on a diverse dataset encompassing variable seed loadings and cooling profiles. The feature-engineered LSTM model consistently outperformed its non-engineered counterpart, particularly under nonlinear cooling conditions where crystallization dynamics were the most complex. This approach offers a practical alternative to mechanistic models and spectroscopic process analytical technology (PAT) tools by enabling accurate prediction of chord length distribution (CLD) metrics from routinely collected data. The framework is easily transferable to other crystallization systems and provides a low-complexity, high-accuracy tool for accelerating lab-scale crystallization development. Full article

(This article belongs to the Special Issue Industrial Applications of Modeling Tools)

► Show Figures

Figure 1

16 pages, 3183 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Relationship Between Density and Structure of Lignins Obtained from Different Feedstocks Pretreated with Protic Ionic Liquids

by Francisco Malaret, Pedro Y. S. Nakasu, Pedro Verdía Barbará, Cynthia Hopson and Jason Hallett

Processes 2025, 13(6), 1848; https://doi.org/10.3390/pr13061848 - 11 Jun 2025

Cited by 1 | Viewed by 684

Abstract

Lignin, one of the most abundant biopolymers on Earth, holds significant promise as a feedstock for applications such as resins, biofuels, foams, and carbon fibres. However, despite extensive research, lignin remains largely underutilised, with its primary use limited to combustion for energy. While [...] Read more.

Lignin, one of the most abundant biopolymers on Earth, holds significant promise as a feedstock for applications such as resins, biofuels, foams, and carbon fibres. However, despite extensive research, lignin remains largely underutilised, with its primary use limited to combustion for energy. While lignin’s structural features are well documented, there is a lack of consistent data on its key physical properties such as density. This study addresses that gap by providing experimentally determined values for skeletal and bulk densities of lignins obtained through different extraction methods, including Kraft; soda pulping; and particularly the ionoSolv process, using ionic liquids such as N,N-dimethyl butyl ammonium hydrogen sulphate ([DMBA][HSO₄]). The results reveal correlations between lignin chemical structure and density in ionoSolv-extracted lignins from Eucalyptus Red Grandis, suggesting opportunities to tune the extraction parameters for targeted material properties. The skeletal density of the lignin samples ranged from 1.3370 to 1.4598 g/cm³, while the bulk density varied more widely—from 0.0944 to 0.5302 g/cm³—reflecting significant differences in particle packing and porosity depending on the biomass source and extraction method. These findings contribute valuable data for process design and scale-up, advancing the commercial viability of lignin-based products. Full article

(This article belongs to the Special Issue Ionic Liquid Applications in Sustainable Biomass Processing)

► Show Figures

Figure 1

22 pages, 5474 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

3D Printing of Optimized Titanium Scaffold for Bone Replacement

by Parvathi Nathan, Siaw Meng Chou and Wai Yee Yeong

Processes 2025, 13(6), 1827; https://doi.org/10.3390/pr13061827 - 9 Jun 2025

Viewed by 855

Abstract

Critical-sized bone defects or CSDs result from bone loss due to trauma, tumor removal, congenital defects, or degenerative diseases. Though autologous bone transplantation is the current gold standard in treating CSDs, its limitations include donor-site morbidity, unavailability of donor bone tissues, risk of [...] Read more.

Critical-sized bone defects or CSDs result from bone loss due to trauma, tumor removal, congenital defects, or degenerative diseases. Though autologous bone transplantation is the current gold standard in treating CSDs, its limitations include donor-site morbidity, unavailability of donor bone tissues, risk of infection, and mismatch between the bone geometry and the defect site. Customized scaffolds fabricated using 3D printing and biocompatible materials can provide mechanical integrity and facilitate osseointegration. Ti-6Al-4V (Ti64) is one of the most widely used commercial alloys in orthopedics. To avoid elastic modulus mismatch between bones and Ti64, it is imperative to use porous lattice structures. Ti64 scaffolds with diamond, cubic, and triply periodic minimal surface (TPMS) gyroid lattice architectures were fabricated using selective laser melting (SLM)with pore sizes ranging from 300 to 900 μm using selective laser melting and evaluated for mechanical and biological performance. Increasing pore size led to higher porosity (up to 90.54%) and reduced mechanical properties. Young’s modulus ranged from 13.18 GPa to 1.01 GPa, while yield stress decreased from 478.16 MPa to 14.86 MPa. Diamond and cubic scaffolds with 300–600 μm pores exhibited stiffness within the cortical bone range, while the 900 μm diamond scaffold approached trabecular stiffness. Gyroid scaffolds (600–900 μm) also showed modulus and yield strength within the cortical bone range but were not suitable for trabecular applications due to their higher stiffness. Cytocompatibility was confirmed through leachate analysis and DAPI-stained osteoblast nuclei. The biological evaluation reported maximum cell adherence in lower pore sizes, with gyroid scaffolds showing a statistically significant (p < 0.01) increase in cell proliferation. These findings suggest that 300–600 μm lattice scaffolds offer an optimal balance between mechanical integrity and biological response for load-bearing bone repair. Full article

(This article belongs to the Special Issue Recent Advances in Additive Manufacturing and 3D Printing)

► Show Figures

Figure 1

38 pages, 6125 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advances in Reinforcement Learning for Chemical Process Control

by Venkata Srikar Devarakonda, Wei Sun, Xun Tang and Yuhe Tian

Processes 2025, 13(6), 1791; https://doi.org/10.3390/pr13061791 - 5 Jun 2025

Cited by 1 | Viewed by 2949

Abstract

This paper reviews the recent advancements of reinforcement learning (RL) for chemical process control. RL presents a systematic strategy in which the machine learning agent learns a policy of actions based on interactions with the environment. We first provide a brief overview of [...] Read more.

This paper reviews the recent advancements of reinforcement learning (RL) for chemical process control. RL presents a systematic strategy in which the machine learning agent learns a policy of actions based on interactions with the environment. We first provide a brief overview of RL theoretic basis built on Markov decision processes (MDPs) and then move onto its application to process control. With particular interest in chemical processes, we review state-of-the-art research developments on RL for controller tuning and direct control policy learning. This work highlights the importance of safe RL control to incorporate deterministic or probabilistic safety constraints such as constrained MDPs, control barrier functions, etc. We conclude the review with a discussion on some of the outstanding challenges such as sampling efficiency, generalizability, uncertainty, and observability, as well as the emergent and future directions to address these limitations. Full article

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

► Show Figures

Figure 1

13 pages, 881 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Free Radical Formation in a Pharmaceutical Product Containing Bisoprolol Fumarate Stored Under Different Physical Conditions

by Kacper Sobczak, Barbara Pilawa, Magdalena Zdybel and Ewa Chodurek

Processes 2025, 13(6), 1742; https://doi.org/10.3390/pr13061742 - 1 Jun 2025

Viewed by 525

Abstract

The pharmaceutical product is a powdered tablets containing bisoprolol fumarate that is used in the treatment of circulatory system diseases. They were examined by X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The aim of this work was to determine the influence of the [...] Read more.

The pharmaceutical product is a powdered tablets containing bisoprolol fumarate that is used in the treatment of circulatory system diseases. They were examined by X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The aim of this work was to determine the influence of the physical conditions of storage on the properties and content of free radicals in this pharmaceutical product. The product was subjected to a temperature of 50 °C, UVA radiation, and UVA radiation and then a temperature of 50 °C. The amplitude, integral intensity, linewidth of EPR lines, and g factor, were analyzed. Free radicals were formed in all tested samples; thus, the product containing bisoprolol fumarate should not be stored at a temperature of 50 °C, and it should be protected from UVA radiation, which is in line with the manufacturer’s requirements. The content of free radicals in the examined product was highest after treatment at a temperature of 50 °C. The lowest free radical content characterized the product after the interaction of both UVA radiation and a temperature of 50 °C. EPR lines were not microwave saturated below a power of 70 mW, which indicates fast spin-lattice relaxation processes in the product. It has been demonstrated that free radical formation in the product containing bisoprolol fumarate depends on the type of physical factor. Full article

(This article belongs to the Special Issue Studies of the Dosage Form and Stability of the Drug by Various Techniques, 2nd Edition)

► Show Figures

Figure 1

19 pages, 11808 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Computational Fluid Dynamics and Population Balance Model Enhances the Smart Manufacturing and Performance Optimization of an Innovative Precipitation Reactor

by Antonello Raponi, Diego Fida, Fabrizio Vicari, Andrea Cipollina and Daniele Marchisio

Processes 2025, 13(6), 1721; https://doi.org/10.3390/pr13061721 - 31 May 2025

Viewed by 1647

Abstract

In this study, we propose the study of an innovative precipitation prototype designed by ResourSEAs, guided by a CFD-PBM (Computational Fluid Dynamics and Population Balance Model) approach, aiming to understand the influence of reactant concentration and nozzle orientation on precipitation processes. The first [...] Read more.

In this study, we propose the study of an innovative precipitation prototype designed by ResourSEAs, guided by a CFD-PBM (Computational Fluid Dynamics and Population Balance Model) approach, aiming to understand the influence of reactant concentration and nozzle orientation on precipitation processes. The first part of the study examines the effect of reactant concentration on supersaturation and the zeroth-order moment (

m_{0}

) within a controlled flow and turbulence fields. Three different concentrations of

{Mg}^{2 +}

(0.1, 0.3, and 0.6 M) and

{OH}^{-}

(0.005, 0.01, and 0.02 M) were tested, resulting in varying supersaturation profiles and

m_{0}

fields. Our results show that, under equal turbulence conditions, increasing the concentration of reactants beyond a certain point actually slows down mixing, which in turn hinders the generation of supersaturation. As a result, supersaturation profiles become nearly identical to those of lower concentrations, despite having consumed more reactants. The second part of this study focuses on the effect of nozzle orientation and positioning along the prototype axis on reactant mixing and particle formation. The simulations reveal that nozzle orientation has a significant impact on the formation of primary particles, especially when positioned in low-velocity regions, leading to slower mixing and greater particle growth. Conversely, high-velocity regions promote faster mixing and more intense aggregation. These findings highlight the interplay between concentration, nozzle orientation, and flow conditions in determining precipitation efficiency, offering insights for optimizing reactor design in industrial applications. Full article

(This article belongs to the Special Issue Industrial Chemistry Reactions (3rd Edition): Kinetics, Mass and Heat Transfer in View of the Industrial Reactors Design)

► Show Figures

Graphical abstract

9 pages, 433 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Conversion of Biomass to Energy-Rich Gas by Catalyzed Pyrolysis in a Sealed Pressure Reactor

by Pavel Straka and Jaroslav Cihlář

Processes 2025, 13(6), 1692; https://doi.org/10.3390/pr13061692 - 28 May 2025

Viewed by 435

Abstract

The purpose of this work is to present a technologically feasible method for processing different types of biomass into energy-rich gas with a methane content higher than 60 vol.% or a hydrogen content higher than 65 vol.%. Selected biomass samples with different compositions [...] Read more.

The purpose of this work is to present a technologically feasible method for processing different types of biomass into energy-rich gas with a methane content higher than 60 vol.% or a hydrogen content higher than 65 vol.%. Selected biomass samples with different compositions were tested. Samples with an operational particle size were pyrolyzed under well-defined conditions in a sealed pressure reactor, and the influence of process parameters on the gas yield and composition was evaluated. Different metal catalysts were used. It was found that, depending on the catalyst used, slow catalyzed pressure pyrolysis at a final temperature of 400 °C yields a methane-rich gas with up to 70 vol.% CH₄ or a hydrogen-rich gas with up to 75 vol.% H₂. In addition, by-products (oil and biochar) were analyzed and their uses described. In conclusion, under energy-saving conditions, pressure-catalyzed pyrolysis of biomass provides energy-rich gas and other usable products. Full article

(This article belongs to the Special Issue Progress on Biomass Processing and Conversion)

► Show Figures

Figure 1

14 pages, 2524 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Effect of the Higher Temperature and UVA Radiation on the Pharmaceutical Preparation Containing Spironolactone—EPR Examination

by Ewa Burek, Barbara Pilawa, Magdalena Zdybel and Ewa Chodurek

Processes 2025, 13(6), 1696; https://doi.org/10.3390/pr13061696 - 28 May 2025

Viewed by 401

Abstract

Electron paramagnetic resonance (EPR) examination of the effect of storage conditions on properties and contents of free radicals formed in the pharmaceutical preparation containing spironolactone, taking into account physical factors such as UVA radiation and the higher temperature, was conducted. The changes in [...] Read more.

Electron paramagnetic resonance (EPR) examination of the effect of storage conditions on properties and contents of free radicals formed in the pharmaceutical preparation containing spironolactone, taking into account physical factors such as UVA radiation and the higher temperature, was conducted. The changes in amplitude (A), integral intensity (I) and EPR linewidth (ΔB_pp) of the EPR spectra and free radical contents were determined. It was obtained that free radicals are formed during storage of this preparation under three different treatments: 50 °C, under UVA radiation, and under UVA radiation and a temperature of 50 °C. During storage, the preparation containing spironolactone should be protected from temperatures 50 °C and from UVA radiation. A higher content of free radicals is formed in the tested preparation exposed to both UVA and a temperature of 50 °C, than in the preparation exposed only to UVA or only to a temperature of 50 °C. Similar integral intensities (I) were obtained for the tested preparation exposed to a temperature of 50 °C or exposed to UVA radiation. Fast spin-lattice relaxation processes occur in all tested pharmaceutical preparation samples containing spironolactone. The usefulness of EPR spectral analysis in the study of free radicals formed in pharmaceutical preparations has been confirmed. Full article

(This article belongs to the Special Issue Studies of the Dosage Form and Stability of the Drug by Various Techniques, 2nd Edition)

► Show Figures

Figure 1

17 pages, 2112 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Photoautotrophic Production of Eicosapentaenoic Acid (EPA) with Nannochloropsis oceanica Under Dynamic Climate Simulations

by Anna-Lena Thurn, Sebastian Gerwald, Thomas Brück and Dirk Weuster-Botz

Processes 2025, 13(6), 1649; https://doi.org/10.3390/pr13061649 - 24 May 2025

Viewed by 832

Abstract

Marine microalgae from the genus Nannochloropsis are promising candidates for the photoautotrophic production of eicosapentaenoic acid (EPA, C20:5), a polyunsaturated fatty acid known for its numerous health benefits. A recent study demonstrated that Microchloropsis salina can accumulate high amounts of EPA when cultivated [...] Read more.

Marine microalgae from the genus Nannochloropsis are promising candidates for the photoautotrophic production of eicosapentaenoic acid (EPA, C20:5), a polyunsaturated fatty acid known for its numerous health benefits. A recent study demonstrated that Microchloropsis salina can accumulate high amounts of EPA when cultivated in flat-plate gas-lift photobioreactors. This study aimed to characterize an alternative strain, Nannochloropsis oceanica, and compare its biomass and EPA productivity to M. salina. Applying simulated dynamic climate conditions of a repeated sunny summer day in Eastern Australia, N. oceanica was cultivated in LED-illuminated flat-plate gas-lift photobioreactors. The results showed significantly higher biomass growth and EPA contents compared to M. salina. An EPA productivity of 33.0 ± 0.6 mg_EPA L⁻¹ d⁻¹ has been achieved in batch processes with N. oceanica. Scaling up the photoautotrophic process to 8 m² thin-layer cascade photobioreactors resulted in doubled concentrations of N. oceanica biomass compared to laboratory-scale batch processes. This improvement was likely due to the reduced fluid layer depth, which enhanced light availability to the microalgal cells. Using urea instead of nitrate as a nitrogen source further improved the EPA production of N. oceanica in thin-layer cascade photobioreactors, achieving CDW concentrations of up to 17.7 g L⁻¹ and thus a high EPA concentration of 843 mg L⁻¹. These findings highlight N. oceanica as an alternative to M. salina for sustainable EPA production, offering potential for further industrial applications. Full article

(This article belongs to the Special Issue Biochemical Processes for Sustainability, 2nd Edition)

► Show Figures

Figure 1

35 pages, 2601 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Isolation, Identification, and Characterization of Probiotic Properties of Lactic Acid Bacterial Strains Isolated from Rose Blossom of Rosa damascena Mill

by Zapryana Denkova, Polina Zapryanova, Yordanka Gaytanska, Bogdan Goranov, Vesela Shopska, Rositsa Denkova-Kostova and Georgi Kostov

Processes 2025, 13(6), 1644; https://doi.org/10.3390/pr13061644 - 23 May 2025

Viewed by 886

Abstract

This study on the isolation, identification, and characterization of the probiotic properties of lactic acid bacterial strains from the rose blossom of Rosa damascena Mill. (R. damascena) is crucial for discovering novel, plant-derived probiotics with potential health benefits and applications in [...] Read more.

This study on the isolation, identification, and characterization of the probiotic properties of lactic acid bacterial strains from the rose blossom of Rosa damascena Mill. (R. damascena) is crucial for discovering novel, plant-derived probiotics with potential health benefits and applications in food, medicine, and cosmetics. Nine lactic acid bacterial (LAB) strains were isolated from rose blossom of R. damascena, and they were identified to the species level by applying physiological and biochemical (API 50 CHL), and molecular genetic (16S rRNA gene sequencing) methods. The isolates were identified as belonging to the Lactobacillus helveticus, Lactobacillus acidophilus, and Lactiplantibacillus plantarum species. Some probiotic properties of the newly isolated and identified LAB strains were examined: their antibacterial activity against pathogens by the agar well diffusion method, and their antibiotic resistance profile by the agar paper disc diffusion method. The LAB strains studied demonstrated significant antibacterial activity against the Escherichia coli, Staphylococcus aureus, Salmonella Abony, Proteus vulgaris, Listeria monocytogenes, and Enterococcus faecalis pathogens and were resistant to most of the antibiotics used in clinical practice, which in turn suggested the possibility of their joint inclusion in therapy, in the composition of probiotic preparations. A batch fermentation process was conducted with Lactiplantibacillus plantarum 5/20, and the kinetic parameters of the batch fermentation process were determined in order to obtain a concentrate with a high viable cell count (10¹³CFU/cm³). The resultant concentrate was freeze-dried, and freeze-dried preparations with a high viable cell count (over 10¹² CFU/g) were obtained. Research on LAB strains isolated from R. damascena could reveal valuable LAB strains with significant probiotic properties. These strains will be suitable for various applications in the composition of starter cultures for functional beverages and foods, as well as probiotic preparations, showcasing the untapped potential of plant-associated microbiota. Full article

(This article belongs to the Special Issue Feature Papers in the "Food Process Engineering" Section)

► Show Figures

Figure 1

27 pages, 1721 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Biologically Active Components of Milk—Production and Properties of Lactoferrin

by Monika Ostrowska, Bartosz Brzozowski, Andrzej Babuchowski and Marek Adamczak

Processes 2025, 13(6), 1620; https://doi.org/10.3390/pr13061620 - 22 May 2025

Viewed by 776

Abstract

The aim of this article was to present the biological activity of milk components, particularly lactoferrin (LF), and techniques for its extraction and purification. Dairy products have long been recognized for their significant contributions to human health and nutrition. Recent studies indicate that [...] Read more.

The aim of this article was to present the biological activity of milk components, particularly lactoferrin (LF), and techniques for its extraction and purification. Dairy products have long been recognized for their significant contributions to human health and nutrition. Recent studies indicate that dairy consumption offers various health benefits, particularly concerning bone health, metabolic wellness, and cardiovascular health. LF, abundantly present in milk, exhibits a range of health-promoting properties that are increasingly recognized for their significance in nutrition and disease prevention. The production of LF can be approached through two main avenues: extraction from milk and recombinant expression systems. Both methods present unique advantages and challenges that influence the efficiency of LF production on an industrial scale. Moreover, advances in purification and drying techniques are crucial to enhance the overall efficiency of LF production. Recent studies have focused on methods such as monolithic ion-exchange chromatography and membrane technologies to improve yield and reduce costs of LF extraction. These innovations not only facilitate the extraction but also preserve the structural integrity and the functional properties of LF. The article presents the discussion of the applications of the LF in the dairy industry, indicating its growing importance as a functional ingredient in health products. Full article

(This article belongs to the Special Issue Improvement and Innovation in Engineering and Bioprocesses in Dairy Technology)

► Show Figures

Figure 1

28 pages, 1699 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Downstream Processes in a Microalgae Biorefinery: Cascaded Enzymatic Hydrolysis and Pulsed Electric Field as Green Solution

by Gianpiero Pataro, Elham Eslami, Francesco Pignataro and Alessandra Procentese

Processes 2025, 13(6), 1629; https://doi.org/10.3390/pr13061629 - 22 May 2025

Viewed by 1054

Abstract

Microalgae are a promising source of valuable compounds, including proteins, pigments, lipids, vitamins, and ingredients for cosmetics and animal feed. Despite their potential, downstream processing remains a major bottleneck in microalgae biorefineries, particularly in achieving high extraction efficiency with low energy and chemical [...] Read more.

Microalgae are a promising source of valuable compounds, including proteins, pigments, lipids, vitamins, and ingredients for cosmetics and animal feed. Despite their potential, downstream processing remains a major bottleneck in microalgae biorefineries, particularly in achieving high extraction efficiency with low energy and chemical input. While several extraction methods exist, few balance efficiency with selectivity and sustainability. Recently, mild and selective techniques such as Pulsed Electric Field (PEF) and Enzymatic Hydrolysis (EH) have gained attention, both individually and in combination. This review provides the first comprehensive comparative analysis of PEF and EH, emphasizing their mechanisms of action, specific cellular targets, and potential for integration into a cascaded, wet-route biorefinery process. Studies involving PEF, EH, and their sequential application (PEF-EH and EH-PEF) are analyzed, focusing on microalgae species, operational conditions, and extraction yields. The advantages and challenges of each method, including compound selectivity, environmental impact, and economic feasibility, are critically evaluated. The goal is to gain insight into whether the synergistic use of PEF and EH can enhance the recovery of intracellular compounds while improving the overall sustainability and efficiency of microalgae-based bioprocessing. Full article

(This article belongs to the Special Issue Process Intensification towards Sustainable Biorefineries)

► Show Figures

Figure 1

33 pages, 1600 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Utilisation of Different Types of Glass Waste as Pozzolanic Additive or Aggregate in Construction Materials

by Karolina Bekerė and Jurgita Malaiškienė

Processes 2025, 13(5), 1613; https://doi.org/10.3390/pr13051613 - 21 May 2025

Viewed by 918

Abstract

Unprocessed glass waste is commonly disposed of in landfills, posing a significant environmental threat worldwide due to its non-biodegradable nature and long decomposition period. The volume of this waste continues to increase annually, driven by increasing consumption of electronic and household devices, as [...] Read more.

Unprocessed glass waste is commonly disposed of in landfills, posing a significant environmental threat worldwide due to its non-biodegradable nature and long decomposition period. The volume of this waste continues to increase annually, driven by increasing consumption of electronic and household devices, as well as the growing popularity and end-of-life disposal of solar panels and other glass products. Therefore, to promote the development of the circular economy and the principles of sustainability, it is necessary to address the problem of reusing this waste. This review article examines the chemical and physical properties of various types of glass waste, including window glass, bottles, solar panels, and glass recovered from discarded electronic and household appliances. It was determined that the most promising and applicable reuse, which does not require high energy consumption, could be in the manufacture of concrete, which is the most developed construction material worldwide. Glass waste can be incorporated into concrete in three different particle sizes according to their function: (a) cement-sized particles, used as a partial binder replacement; (b) sand-sized particles, replacing fine aggregate; and (c) coarse aggregate-sized particles, substituting natural coarse aggregate either partially or fully. The article analyses the impact of glass waste on the properties of concrete or binder, presents controversial results, and provides recommendations for future research. In addition, the advantages and challenges of incorporating glass waste in ceramics and asphalt concrete are highlighted. Full article

(This article belongs to the Special Issue Green Chemistry: From Wastes to Value-Added Products (2nd Edition))

► Show Figures

Figure 1

19 pages, 1349 KiB

Open AccessFeature PaperEditor’s ChoiceReview

N-Nitrosamines in Meat Products: Formation, Detection and Regulatory Challenges

by Tomislav Rot, Dragan Kovačević, Kristina Habschied and Krešimir Mastanjević

Processes 2025, 13(5), 1555; https://doi.org/10.3390/pr13051555 - 17 May 2025

Cited by 1 | Viewed by 1917

Abstract

Nitrosamines (NAs) are a class of chemical compounds predominantly formed during the processing, curing, and storage of meat products through the reaction of nitrites with amines. Decades of toxicological and epidemiological evidence have unequivocally established several NAs as potent human carcinogens, with strong [...] Read more.

Nitrosamines (NAs) are a class of chemical compounds predominantly formed during the processing, curing, and storage of meat products through the reaction of nitrites with amines. Decades of toxicological and epidemiological evidence have unequivocally established several NAs as potent human carcinogens, with strong associations with gastrointestinal, pancreatic, and liver cancers. This review critically examines the pathways of NA formation in meat, the influence of processing conditions, and the factors contributing to their variability in food products. It also outlines state-of-the-art analytical techniques for their detection and summarizes recent scientific efforts to reduce their formation. Despite scientific consensus on the health hazards posed by dietary exposure to NAs, regulatory control remains fragmented and insufficient. Therefore, this review highlights the pressing need for coordinated international action and the development of a harmonized regulatory framework to mitigate public health risks. Full article

(This article belongs to the Special Issue Food Biochemistry and Health: Recent Developments and Perspectives)

9 pages, 1603 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electron Emission as a Tool for Detecting Fracture and Surface Durability of Tensile-Loaded Epoxy Polymers Modified with SiO₂ Nanoparticles

by Agnes Elizabeth Cerpa, Yuri Dekhtyar and Sanda Kronberga

Processes 2025, 13(5), 1546; https://doi.org/10.3390/pr13051546 - 17 May 2025

Viewed by 401

Abstract

Epoxy polymers modified with nanoparticles are increasingly employed due to their enhanced performance in aggressive environments, characterized by mechanical stress, radiation exposure, and extreme temperatures. The mechanical failure of these polymers is attributed to the fracturing of atomic and molecular bonds, that subsequently [...] Read more.

Epoxy polymers modified with nanoparticles are increasingly employed due to their enhanced performance in aggressive environments, characterized by mechanical stress, radiation exposure, and extreme temperatures. The mechanical failure of these polymers is attributed to the fracturing of atomic and molecular bonds, that subsequently excites electrons having the capability to be emitted from the nanolayer of the material. The present study demonstrates that the relationship between mechanical loading and electron emission over time serves as an indicator of surface loading and durability. By utilizing the Kinetic Nature of Solid Material Strength (KSMS) theory alongside near-threshold electron emission measurements, the article presents the behavior of epoxy polymers modified with SiO₂ nanoparticles under tensile loading. The results indicate that as mechanical load is applied, photoelectron emission (PE) pulses emerge. Notably, the pulse spectrum highest frequency (fmax) correlates with the time of atomic fluctuations (τ), defined by τ = 1/fmax. Furthermore, ultraviolet (UV) irradiation of the nanoparticles prior to mixing with the polymer is shown to influence the parameter of KSMS responsible for local stress concentration. This suggests that PE is connected with the homogeneity of the composite too. The achieved results demonstrate that PE contactless measurements can be used to detect mechanical destruction of the epoxy polymer composite surface nanolayer, as well as to assess its durability and corresponding activation energy. The results presented in the article may contribute to the development of more reliable epoxy polymer composites and durability measurements of their mechanically loaded surface layer or nanofilms. Full article

(This article belongs to the Special Issue Composite Materials Processing, Modeling and Simulation)

► Show Figures

Figure 1

19 pages, 4266 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Accurate and Efficient Process Modeling and Inverse Optimization for Trench Metal Oxide Semiconductor Field Effect Transistors: A Machine Learning Proxy Approach

by Mingqiang Geng, Jianming Guo, Yuting Sun, Dawei Gao and Dong Ni

Processes 2025, 13(5), 1544; https://doi.org/10.3390/pr13051544 - 16 May 2025

Viewed by 869

Abstract

This study proposes a novel framework integrating long short-term memory (LSTM) networks with Bayesian optimization (BO) to address process–device co-optimization challenges in trench-gate metal–oxide–semiconductor field-effect transistor (MOSFET) manufacturing. Conventional TCAD simulations, while accurate, suffer from computational inefficiency in high-dimensional parameter spaces. To overcome [...] Read more.

This study proposes a novel framework integrating long short-term memory (LSTM) networks with Bayesian optimization (BO) to address process–device co-optimization challenges in trench-gate metal–oxide–semiconductor field-effect transistor (MOSFET) manufacturing. Conventional TCAD simulations, while accurate, suffer from computational inefficiency in high-dimensional parameter spaces. To overcome this, an LSTM-based TCAD proxy model is developed, leveraging hierarchical temporal dependencies to predict electrical parameters (e.g., breakdown voltage, threshold voltage) with deviations below 3.5% compared to physical simulations. The model, validated on both N-type and P-type 20 V trench MOS devices, outperforms conventional RNN and GRU architectures, reducing average relative errors by 1.78% through its gated memory mechanism. A BO-driven inverse optimization methodology is further introduced to navigate trade-offs between conflicting objectives (e.g., minimizing on-resistance while maximizing breakdown voltage), achieving recipe predictions with a maximum deviation of 8.3% from experimental data. Validation via TCAD-simulated extrapolation tests and SEM metrology confirms the framework’s robustness under extended operating ranges (e.g., 0–40 V drain voltage) and dimensional tolerances within industrial specifications. The proposed approach establishes a scalable, data-driven paradigm for semiconductor manufacturing, effectively bridging TCAD simulations with production realities while minimizing empirical trial-and-error iterations. Full article

(This article belongs to the Special Issue Machine Learning Optimization of Chemical Processes)

► Show Figures

Figure 1

23 pages, 6860 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Energy and Exergy Analysis of Modified Heat Pump for Simultaneous Production of Cooling and Water Desalination Using Diverse Refrigerants

by A. Pacheco-Reyes, J. C. Jimenez-Garcia, J. Delgado-Gonzaga and W. Rivera

Processes 2025, 13(5), 1510; https://doi.org/10.3390/pr13051510 - 14 May 2025

Viewed by 527

Abstract

More efficient energy conversion systems operating with clean energy sources or utilizing waste heat are crucial to minimizing the negative environmental impact associated with conventional systems. This study presents the energy and exergy analysis of a modified heat pump capable of producing cooling [...] Read more.

More efficient energy conversion systems operating with clean energy sources or utilizing waste heat are crucial to minimizing the negative environmental impact associated with conventional systems. This study presents the energy and exergy analysis of a modified heat pump capable of producing cooling and desalinated water using heat dissipated in the condenser. Six refrigerants were analyzed in the theoretical evaluation of the proposed system. These were selected based on their use in vapor compression systems and their thermodynamic properties. A parametric study considering operating temperatures and relative humidities determined that refrigerant R-123 achieved the greatest benefits in terms of the EER, the GOR, and

η_{E x e r g y}

. In contrast, the highest benefits in water desalination were obtained with refrigerant R-410a. For operating conditions of T_E = 0 °C, T_C = 34 °C, and T_CA = 14 °C, the system using refrigerant R-123 achieved an EER, GOR,

η_{E x e r g y}

, D_W, and I_T of 0.82, 2.51, 0.35, 3.46 L/h, and 0.55 kW, respectively. Additionally, the dehumidifier and the evaporator were the components contributing the highest irreversibilities, accounting for approximately 24% and 19.3%, respectively. Full article

(This article belongs to the Special Issue Thermal Engineering: Energy Conversion, Numerical Simulation, and Advanced Control)

► Show Figures

Figure 1

15 pages, 3161 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Characterisation of Cork Volatile Organic Compounds Using TD-GC-MS: Effects of Origin, Washing Process, and Thermal Processing of Cork Stoppers

by Patricia Jové, Raquel de Nadal, Maria Verdum and Núria Fiol

Processes 2025, 13(5), 1505; https://doi.org/10.3390/pr13051505 - 14 May 2025

Viewed by 450

Abstract

This study presents a green and solvent-free methodology based on thermal desorption coupled to gas chromatography-mass spectrometry (TD-GC-MS) to characterise cork’s volatile aromatic (VOC) profile. Samples from three geographical origins—Catalonia, Extremadura, and Sardinia—were analysed at different extraction temperatures. Cork stoppers from Sardinia were [...] Read more.

This study presents a green and solvent-free methodology based on thermal desorption coupled to gas chromatography-mass spectrometry (TD-GC-MS) to characterise cork’s volatile aromatic (VOC) profile. Samples from three geographical origins—Catalonia, Extremadura, and Sardinia—were analysed at different extraction temperatures. Cork stoppers from Sardinia were also analysed after two washing procedures (immersion and spray) and thermal treatment. The results showed that temperature and geographical origin significantly influenced the quantity and intensity of extracted VOCs, with higher extraction temperatures yielding a more comprehensive volatile profile. Vanillin was the most abundant compound in all samples. A multivariate analysis showed that cork from Extremadura was associated with carboxylic acids, Catalonia with furan derivatives and sugar-related compounds, and Sardinia with phenolic compounds linked to lignin degradation. Immersion-washed stoppers retained more lignin-derived and phenolic compounds, while spray-washed samples were characterised by a higher alkane content. Thermal treatment notably altered the VOC profile, increasing ketones such as acetophenone and 2-nonadecanone and reducing alkanes and fatty acids. These findings highlight the influence of the geographical origin and manufacturing process on the aromatic composition of cork, with potential applications in industries seeking natural active compounds. Full article

(This article belongs to the Special Issue Applications of Chromatographic Separation Techniques in Food and Chemistry—Second Edition)

► Show Figures

Figure 1

14 pages, 2644 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mining Biosynthetic Gene Clusters of Bacillus subtilis MGE 2012 Using Whole Genome Sequencing

by Jiyoun Kim, Hafiza Hira Bashir, Joon Hwang and Gi-Seong Moon

Processes 2025, 13(5), 1503; https://doi.org/10.3390/pr13051503 - 14 May 2025

Viewed by 765

Abstract

This study aims to elucidate the genomic characteristics of Bacillus subtilis MGE 2012, a strain isolated from Korean traditional fermented food, meju, which contributes to its high enzyme activity and potential applications. The whole genome sequence of B. subtilis MGE 2012 was assembled [...] Read more.

This study aims to elucidate the genomic characteristics of Bacillus subtilis MGE 2012, a strain isolated from Korean traditional fermented food, meju, which contributes to its high enzyme activity and potential applications. The whole genome sequence of B. subtilis MGE 2012 was assembled using MEGAHIT, annotated using RAST and BLASTKOALA v3.1. Phylogenetic analysis placed MGE 2012 within the Bacillus clade, showing high similarity to B. subtilis NCIB 3610 and B. subtilis ATCC 6051. AntiSMASH analysis identified 14 biosynthetic gene clusters (BGCs) capable of producing various secondary metabolites, including subtilosin, bacillibactin, fengycin, bacilysin, plipastatin, and surfactin. This study provides an overview of the whole genome and secondary metabolite profile of B. subtilis MGE 2012, emphasizing its potential applications in biotechnology. While the primary focus of this study was to explore the genomic characteristics and secondary metabolite profile, future research could delve deeper into genome mining for enzyme activities and their applications. Full article

(This article belongs to the Special Issue Computational Biology Approaches to Genome and Protein Analyzes)

► Show Figures

Figure 1

13 pages, 3003 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Extraction-Based Pretreatment of End-of-Life Plastics from Waste Electrical and Electronic Equipment for Brominated Flame Retardant Removal and Subsequent Valorization via Pyrolysis

by Maria-Anna Charitopoulou, Maria Papadimitriou, Lambrini Papadopoulou and Dimitriοs S. Achilias

Processes 2025, 13(5), 1458; https://doi.org/10.3390/pr13051458 - 9 May 2025

Viewed by 590

Abstract

Due to the increasing volumes of plastic waste generated from electric and electronic devices, research has focused on the investigation of recycling methods for their safe handling. Pyrolysis converts plastics from waste electric and electronic equipment (WEEE) into valuable products (pyrolysis oil). Nevertheless, [...] Read more.

Due to the increasing volumes of plastic waste generated from electric and electronic devices, research has focused on the investigation of recycling methods for their safe handling. Pyrolysis converts plastics from waste electric and electronic equipment (WEEE) into valuable products (pyrolysis oil). Nevertheless, the frequent presence of flame retardants, mainly brominated flame retardants (BFR), hinders pyrolysis’s wide application, since hazardous compounds may be produced, limiting the use of pyrolysis oils. Taking the aforementioned into account, this work focuses on the recycling, via pyrolysis, of various plastic samples gathered from WEEE, to explore the valuable products that are formed. Specifically, 14 plastic samples were collected, including parts of computer peripheral equipment, remote controls, telephones and other household appliances. Considering the difficulties when BFRs are present, the study went one step further, applying XRF analysis to identify their possible presence, and then Soxhlet extraction as an environmentally friendly method for the debromination of the samples. Based on the XRF results, it was found that 23% of the samples contained bromine. After each Soxhlet extraction, bromine was reduced, achieving a complete removal in the case of a remote control sample and when butanol was the solvent. Thermal pyrolysis led to the formation of valuable products, including the monomer styrene and other secondary useful compounds, such as alpha-methylstyrene. The FTIR results, in combination with the pyrolysis products, enabled the identification of the polymers present in the samples. Most of them were ABS or HIPS, while only three samples were PC. Full article

(This article belongs to the Special Issue Municipal Solid Waste for Energy Production and Resource Recovery)

► Show Figures

Graphical abstract

24 pages, 863 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Operational Temperature Optimization in Hydrogen Turbine Blades via Time-Fractional Conformable Sensitivity Analysis

by Josué Neftalí Gutiérrez-Corona, Oscar Oswaldo Sánchez-Sánchez, Marco Antonio Polo-Labarrios and Guillermo Fernandez-Anaya

Processes 2025, 13(5), 1430; https://doi.org/10.3390/pr13051430 - 7 May 2025

Viewed by 1017

Abstract

This study focuses on optimizing the thermal performance of hydrogen turbine blades through a sensitivity analysis using generalized fractional calculus. The approach is designed to capture the transient temperature dynamics and optimize thermal profiles by analyzing the influence of a fractional-order parameter on [...] Read more.

This study focuses on optimizing the thermal performance of hydrogen turbine blades through a sensitivity analysis using generalized fractional calculus. The approach is designed to capture the transient temperature dynamics and optimize thermal profiles by analyzing the influence of a fractional-order parameter on the system’s behavior. The model was implemented in Python, using Monte Carlo simulations to evaluate the impact of the parameter on the temperature evolution in different thermal regimes. Three distinct regions were identified: the Quasi-Uniform Region (where fractional effects are negligible), the Sub-Classical Region (characterized by delayed thermal behavior), and the Super-Classical Region (exhibiting enhanced heat accumulation). Regression analyses reveal quadratic and cubic dependencies of blade temperature on the fractional-order parameter, confirming the robustness of the model with R² values greater than 0.96. The study highlights the potential of using fractional calculus to optimize the thermal response of turbine blades, helping to identify the most suitable parameters for faster stabilization and efficient heat management in hydrogen turbines. Furthermore, it was found that by adjusting the fractional-order parameter, the system can be optimized to reach equilibrium more rapidly while achieving higher temperatures. Importantly, the equilibrium is not altered but rather accelerated based on the chosen parameter, ensuring a more efficient thermal stabilization process. Full article

(This article belongs to the Special Issue Modeling and Optimization for Multi-scale Integration)

► Show Figures

Figure 1

10 pages, 2158 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Assessment of Performance of Short Cuboid Packed-Bed Devices Based on Simulations and Experiments

by Guoqiang Chen and Raja Ghosh

Processes 2025, 13(5), 1400; https://doi.org/10.3390/pr13051400 - 4 May 2025

Viewed by 337

Abstract

Cuboid packed-bed devices developed for chromatographic separation typically have shorter bed heights and larger cross-sectional areas than their equivalent cylindrical columns. These devices can be operated at low back pressures and give comparable or even better resolution than their equivalent columns. However, the [...] Read more.

Cuboid packed-bed devices developed for chromatographic separation typically have shorter bed heights and larger cross-sectional areas than their equivalent cylindrical columns. These devices can be operated at low back pressures and give comparable or even better resolution than their equivalent columns. However, the bed height of a cuboid packed-bed device could potentially affect its separation performance. To examine this, three devices having 5, 10 and 19.5 mm bed heights were fabricated and packed with the same resin media. A mathematical model was first developed to predict the effect of bed height on the performance of these cuboid devices. This prediction was performed based on the residence time heterogeneity (RTH) in these devices, which increased slightly as the bed height was decreased. However, this was not likely to affect the separation efficiency very significantly. The relative performances of these three cuboid devices were then compared based on the resolution obtained during ion-exchange chromatography of multi-protein mixtures. As predicted by the mathematical model, the loss in resolution due to the decrease in bed height was relatively small (0.83 to 0.73 in binary protein separation). Also, this loss could easily be compensated for by slightly lowering the flow rate or by extending the elution gradient. The results discussed in this paper demonstrate that with cuboid packed-bed devices, the dimensions could be altered in a reasonably flexible manner without adversely affecting separation performance. Such flexibility is advantageous from the point of view of process design and optimization, which is critically important for developing large-scale processes for the purification of biologics. Full article

(This article belongs to the Special Issue New Frontiers in Chromatographic Separation Technology)

► Show Figures

Figure 1

17 pages, 2914 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigation of the Possibilities for the Recycling of Mixed Heterogeneous Lead Refinery Waste

by Jasmina Dedić, Jelena Đokić, Gordana Milentijević, Irma Dervišević and Maja Petrović

Processes 2025, 13(5), 1380; https://doi.org/10.3390/pr13051380 - 30 Apr 2025

Viewed by 374

Abstract

The historical industrial waste deposit Gater was used to dispose of different metallurgy wastes from lead and zinc production. The metallurgical waste deposit was situated in the open space, between the tailing waste deposit Žitkovac and river Ibar flow. Large amounts of lead-containing [...] Read more.

The historical industrial waste deposit Gater was used to dispose of different metallurgy wastes from lead and zinc production. The metallurgical waste deposit was situated in the open space, between the tailing waste deposit Žitkovac and river Ibar flow. Large amounts of lead-containing wastes are produced in the non-ferrous metallurgical industry, such as lead ash and lead slag generated in Pb smelting, lead anode slime, and lead sludge produced in the raw lead refining process. In addition to the lead concentration, numerous valuable components are found in the lead refinery waste from the group of Critical Raw Materials, such as antimony, arsenic, bismuth, copper, nickel, magnesium, scandium, as well as Rare-Earth Elements. Samples with eight characteristic points were taken to obtain relevant data indicating a possible recycling method. The chemical composition analysis was conducted using ICP; the scanning was completed using SEM-EDS. The mineralogical composition was determined by using XRD. The chemical analysis showed a wide range of valuable metal concentrations, from Ag (in the range from 14.2 to 214.6, with an average 86.25 mg/kg) to heavy metals such as Cu (in the range from 282.7 to 28,298, with an average 10,683.7 mg/kg or 1.0683% that corresponds to some active mines), Ni and Zn (in the range from 1.259 to 69,853.4, with an average 14,304.81 mg/kg), Sc (in the range from 2.4 to 75.3, with an average 33.61 mg/kg), Pb (in the range from 862.6 to 154,027.5, with an average 45,046 mg/kg), Sb (in the range from 51.7 to 18,514.7, with an average 2267.8 mg/kg), Ca (in the range from 167.5 to 63,963, with an average 19,880 mg/kg), Mg (in the range from 668.3 to 76,824.5, with an average 31,670 mg/kg), and As (in the range from 62.9 to 24,328.1, with an average 5829.53 mg/kg). The mineralogy analysis shows that all metals are in the form of oxides, but in the case of As and Fe, SEM-EDS shows some portion of elemental lead, pyrite, and silica-magnesium-calcium oxides as slag and tailing waste residues. The proposed recovery process should start with leaching, and further investigation should decide on the type of leaching procedure and agents, considering the waste’s heterogeneous nature and acidity and toxicity. Full article

(This article belongs to the Special Issue Municipal Solid Waste for Energy Production and Resource Recovery)

► Show Figures

Figure 1

26 pages, 4188 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Valorization of Residual Biomass from Sargassum filipendula for the Extraction of Phlorotannins and Pigments Using Eutectic Solvents

by Pedro Afonso Vasconcelos Paes Mello, Cristiane Nunes da Silva and Bernardo Dias Ribeiro

Processes 2025, 13(5), 1345; https://doi.org/10.3390/pr13051345 - 28 Apr 2025

Viewed by 742

Abstract

Sargassum filipendula is a marine macroalgae, also known as brown algae. These species contain significant amounts of polysaccharides, such as alginates, and phenolic compounds, including phlorotannins, with excellent biological properties. This study evaluated the extraction of bioactive compounds from the residual biomass of [...] Read more.

Sargassum filipendula is a marine macroalgae, also known as brown algae. These species contain significant amounts of polysaccharides, such as alginates, and phenolic compounds, including phlorotannins, with excellent biological properties. This study evaluated the extraction of bioactive compounds from the residual biomass of Sargassum filipendula using deep eutectic solvents based on alkanol amines combined with polyols. The residual biomass presented a content of 7.36% protein, 1.11% lipids, 20.51% ash, 14.88% moisture, 50.25% total fibers, and 5.89% alginate. Preliminary screening identified N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1) and N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1) as the most efficient solvents for the extraction of bioactive compounds. The optimization process showed that the temperature and solid–liquid ratio significantly influenced (p < 0.05) the extraction of total phenolic compounds, phlorotannins, and the content of photosynthetic pigments. Intermediate temperatures (74.4 °C for N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1) and 68.4 °C for N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1), and a lower solid-to-liquid ratio (0.03) were optimal conditions to extract the low-pigment phlorotannins selectively. In contrast, higher temperatures (120 °C) maximized the extraction of phlorotannins and photosynthetic pigments. N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30) extracted 110.64 mg PGE/g phlorotannins and 78.15 mg GAE/g phenolics, while N, N-(dimethylamino)-ethanol:1,3-propanediol (1.83:1) produced 21.57 mg PGE/g and 72.89 mg GAE/g, respectively. The extraction of photosynthetic pigments reached a maximum yield at 120 °C, using N, N-(dimethylamino)-ethanol: benzyl alcohol (1.30:1), with a content of 21.61 µg/g of chlorophylls and 38.11 µg/g of pheophytins, while N, N-(dimethylamino)-ethanol: 1,3-propanediol (1.83:1) provided content of 17.76 µg/g and 36.32 µg/g, respectively. The extracts exhibited antioxidant activity with 0.69 mg TE/mL in scavenging DPPH radicals, 24.42 mg TE/mL in scavenging ABTS radicals, and 2.26 mg TE/mL of iron-reducing antioxidant power. These results demonstrate the potential of DESs for the sustainable recovery of bioactive compounds from Sargassum filipendula residual biomass. Full article

(This article belongs to the Special Issue Green Separation and Purification Processes)

► Show Figures

Figure 1

22 pages, 6261 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Development of a New Bi₁₂ZnO₂₀/AgI Heterosystem for the Degradation of Dye-Contaminated Water by Photocatalysis Under Solar Irradiation: Synthesis, Characterization and Kinetics

by Serine Madji, Mohamed Belmedani, Elhadj Mekatel, Sarra Zouaoui and Seif El Islam Lebouachera

Processes 2025, 13(5), 1342; https://doi.org/10.3390/pr13051342 - 27 Apr 2025

Cited by 1 | Viewed by 828

Abstract

This study explores the efficiency of heterogeneous photocatalysis in wastewater treatment, which is recognized for inducing significant rates of degradation and mineralization of various contaminants, including dyes. The study focuses on the development of an innovative composite via a combination of the sillenite [...] Read more.

This study explores the efficiency of heterogeneous photocatalysis in wastewater treatment, which is recognized for inducing significant rates of degradation and mineralization of various contaminants, including dyes. The study focuses on the development of an innovative composite via a combination of the sillenite type semiconductor Bi₁₂ZnO₂₀ and the halide-type semiconductor AgI. Both semiconductors were synthesized via co-precipitation, and their phases were identified using X-ray diffraction and characterized by scanning electron microscopy, Raman spectroscopy, Brunauer–Emmett–Teller analysis for specific surface area, UV–Visible diffuse reflectance spectroscopy, and the point of zero charge. The evaluation of the photocatalytic activity of the Bi₁₂ZnO₂₀/AgI heterosystem was carried out by monitoring the degradation process of Basic Blue 41 (BB41) under solar irradiation conditions. The results of this study revealed that the Bi₁₂ZnO₂₀/AgI heterosystem achieved the efficient degradation of BB41, with a removal rate of 98% after 150 min of treatment. The mineralization study showed that the TOC value decreased from 19.89 mg L⁻¹ to 6.87 mg L⁻¹, indicating that a significant portion of BB41 was mineralized. Via kinetic research, it was established that the degradation process followed a pseudo-first-order mechanism. Furthermore, recycling tests showed that the synthesized heterostructures maintained good structural stability and acceptable reusability over several cycles. These findings highlight the potential of heterogeneous photocatalysis as a promising approach to addressing environmental challenges associated with azo dyes. Full article

(This article belongs to the Special Issue Advanced Oxidation Processes for Water and Wastewater Treatment: Developments, Challenges, and Opportunities)

► Show Figures

Figure 1

14 pages, 1900 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Preparation of Experimental Resin-Based Dental Composites Using Different Mixing Methods for the Filler and Matrix

by Maja Zalega, Michał Krasowski, Olga Dawicka, Aleksandra Jasińska, Aleksandra Żabecka, Patrycja Kałuża and Kinga Bociong

Processes 2025, 13(5), 1332; https://doi.org/10.3390/pr13051332 - 27 Apr 2025

Viewed by 1181

Abstract

Resin-based composites are common and widely used materials in dentistry in direct and indirect applications. Their mechanical properties depend on the composition and homogeneity of the resulting structure. This study aims to optimize the mixing process to obtain the most homogeneous mixture possible, [...] Read more.

Resin-based composites are common and widely used materials in dentistry in direct and indirect applications. Their mechanical properties depend on the composition and homogeneity of the resulting structure. This study aims to optimize the mixing process to obtain the most homogeneous mixture possible, which will allow for the better mechanical properties of the composite. A mixture of bis-GMA/UDMA/HEMA/TEGDMA monomers forming a polymer matrix was filled with silanized silica (45 wt%) using different mixing methods. This study analyzed five manufacturing methods—hand mixing (agate mortar), mixing in a centrifugal Hauschild SpeedMixer, and the hybrid method—combined with the abovementioned methods. The effect of the mixing method on the Vickers hardness (HV), flexural strength (FS), compressive strength (CS), and diametral tensile strength (DTS) of the produced composites was investigated, and the stresses generated during composite polymerization were determined. Mechanically prepared composites have the highest flexural strength and hardness. The lowest shrinkage stress was achieved by the composite, which was prepared partially manually. The results showed that the mixing method affects the morphology of the filler and, hence, the strength properties of the resulting material. Full article

(This article belongs to the Special Issue Sustainable Innovation in the Production of Green Materials for Advanced Technologies)

► Show Figures

Figure 1

15 pages, 904 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Sustainable Valorization of Plant Residues Through Enzymatic Hydrolysis for the Extraction of Bioactive Compounds: Applications as Functional Ingredients in Cosmetics

by Bruna M. Saorin Puton, Carolina E. Demaman Oro, Julia Lisboa Bernardi, Diana Exenberger Finkler, Luciana D. Venquiaruto, Rogério Marcos Dallago and Marcus V. Tres

Processes 2025, 13(5), 1314; https://doi.org/10.3390/pr13051314 - 25 Apr 2025

Cited by 3 | Viewed by 1037

Abstract

The growing demand for sustainable and environmentally friendly cosmetic products has driven innovations using plant residues as raw materials for high-value-added applications. This study focuses on the enzymatic hydrolysis of plant residues to extract bioactive compounds, with the potential for application as functional [...] Read more.

The growing demand for sustainable and environmentally friendly cosmetic products has driven innovations using plant residues as raw materials for high-value-added applications. This study focuses on the enzymatic hydrolysis of plant residues to extract bioactive compounds, with the potential for application as functional ingredients in cosmetics. Enzymatic processes are highlighted for their ability to optimize extraction, preserving the bioactivity of the compounds while significantly reducing the environmental footprint compared to conventional resource-intensive methods. This work emphasizes scientific articles that incorporate the principles of the circular economy, promoting the reuse of solid waste and mitigating the need to extract new natural resources. The valorization of waste through advanced biotechnological technologies addresses critical environmental challenges and offers innovative solutions that transform agro-industrial by-products into high-value inputs for the cosmetic industry. The results presented reinforce this approach’s feasibility and positive impact, promoting economic and environmental benefits. This study highlights the transformative role of enzymatic hydrolysis in the transition toward a more sustainable, efficient cosmetics industry integrated with global decarbonization goals. Full article

(This article belongs to the Special Issue Advances in Waste Treatment, Bioremediation and Decarbonization Research)

► Show Figures

Figure 1

19 pages, 707 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Nonlinear Back-Calculation Anti-Windup Based on Operator Theory

by Yuuki Morohoshi and Mingcong Deng

Processes 2025, 13(5), 1266; https://doi.org/10.3390/pr13051266 - 22 Apr 2025

Viewed by 464

Abstract

Real-world plants have various nonlinear characteristics such as friction and hysteresis, so nonlinear control is essential for precise control. In addition, actuators of plants have input constraints, which cause the integrator of the controller to windup. So far, anti-windup methods have mainly been [...] Read more.

Real-world plants have various nonlinear characteristics such as friction and hysteresis, so nonlinear control is essential for precise control. In addition, actuators of plants have input constraints, which cause the integrator of the controller to windup. So far, anti-windup methods have mainly been for linear controllers, and research on nonlinear controllers has not been sufficient. This paper proposes a back-calculation anti-windup method for nonlinear controllers. By analyzing and extending the back-calculation anti-windup for a Proportional–Integral controller using operator theory, it can be applied to nonlinear controllers. The proposed method is applied to integral sliding mode control and right coprime factorization. In the simulation, we compared the proposed method with and without its application, as well as with conditional integration, and confirmed the effectiveness of the proposed method. In the future, it is necessary to extend the method to be applicable to more complex systems. This study has the potential to contribute to the practical application of nonlinear control. Full article

(This article belongs to the Special Issue Advances in the Control of Complex Dynamic Systems)

► Show Figures

Figure 1

24 pages, 4367 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of the Influence of Different Plasticizing Systems in a Single-Screw Extruder on the Extrusion-Cooking Process and on Selected Physical Properties of Snack Pellets Enriched with Selected Oilseed Pomace

by Jakub Soja, Maciej Combrzyński, Tomasz Oniszczuk, Marek Gancarz and Renata Różyło

Processes 2025, 13(4), 1247; https://doi.org/10.3390/pr13041247 - 20 Apr 2025

Viewed by 417

Abstract

By-products generated in the agri-food industry are frequently regarded as waste, despite their significant potential for reutilization as valuable raw materials with both nutritional and functional properties. Nigella and flaxseed pomace, as rich sources of bioactive compounds, have the capacity to enhance the [...] Read more.

By-products generated in the agri-food industry are frequently regarded as waste, despite their significant potential for reutilization as valuable raw materials with both nutritional and functional properties. Nigella and flaxseed pomace, as rich sources of bioactive compounds, have the capacity to enhance the nutritional profile and functional characteristics of extruded products while simultaneously contributing to the reduction in food waste. Uniquely, the present study analyzed the effect of extrusion-cooking process conditions on the efficiency, energy consumption, and selected physical properties of extrudates enriched with nigella and flaxseed pomace. The samples were made using a single-screw extruder-cooker. Two plasticizing (L/D 16 and 20) systems were compared. The highest efficiency, 23.16 kg/h, was reached using 20% nigella pomace with the L/D 16 system. During the whole process, the specific mechanical energy ranged from 0.006 to 0.105 kWh/kg. New information was obtained on the interaction between pomace content and the physical properties of the extrudates. The results showed that the use of 10% nigella pomace maximized the WAI 4.90 and WSI 11.73% for pellets with 30% of nigella seed pomace in the L/D 20 and influenced the change in bulk density, indicating a double innovation: an improvement in extrudate quality and the efficient use of by-products. Full article

(This article belongs to the Special Issue Feature Papers in the "Food Process Engineering" Section)

► Show Figures

Figure 1

32 pages, 72179 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impact of Substrate Type on the Properties of Cast Biodegradable Starch-Based Films

by Tomasz Tadeusz Murawski, Zuzanna Żołek-Tryznowska and Jerzy Szałapak

Processes 2025, 13(4), 1197; https://doi.org/10.3390/pr13041197 - 15 Apr 2025

Cited by 1 | Viewed by 508

Abstract

Biodegradable films are a viable alternative to conventional plastics, thereby contributing to environmental pollution reduction. This study investigates the impact of substrate type on the properties of starch-based films produced using a plasticizer-assisted casting method. Four different substrates, namely, glass, copper, copper-free laminate, [...] Read more.

Biodegradable films are a viable alternative to conventional plastics, thereby contributing to environmental pollution reduction. This study investigates the impact of substrate type on the properties of starch-based films produced using a plasticizer-assisted casting method. Four different substrates, namely, glass, copper, copper-free laminate, and Teflon^®, were evaluated, addressing a research gap in which previous studies primarily focused on film composition. The films were analyzed for color, tensile strength, surface free energy, and surface morphology using optical and electron microscopy. The results demonstrated a substrate-dependent impact on surface properties, particularly optical transparency, surface roughness, and adhesion. The films cast on glass and laminate exhibited higher transparency and lower roughness, while copper substrate induced micro-striations and strong adhesion. Teflon^® substrates replicated surface imperfections, which may be advantageous for optical applications, but caused film delamination. Tensile strength did not show statistically significant differences across substrates, although reduced elongation was observed for the films cast on Teflon^®. Water vapor permeability was also not significantly affected, indicating a dominant role of bulk material properties. It averaged 25 kg per day per square meter, which means high vapor permeability. Surface free energy analysis revealed marked variations between top and bottom layers, with values ranging from 35 to 70 mJ·m⁻² depending on the substrate. These findings confirm that the type of casting substrate plays a critical role in determining the surface and optical properties of starch-based films, even at the laboratory scale. This study provides new insights into substrate–film interactions and establishes a foundation for optimizing biodegradable film fabrication for industrial and application-specific needs. Full article

(This article belongs to the Special Issue Development and Characterization of Advanced Polymer Nanocomposites)

► Show Figures

Figure 1

34 pages, 4220 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Effects of Light Quality Adjustment in Microalgal Cultivation: Flashing Light and Wavelength Shifts in Photobioreactor Design

by Arima Marchese, Serena Lima, Alessandro Cosenza, Francesco Giambalvo and Francesca Scargiali

Processes 2025, 13(4), 1159; https://doi.org/10.3390/pr13041159 - 11 Apr 2025

Cited by 1 | Viewed by 1581

Abstract

The distribution of light within a microalgal culture and the choice of the best wavelengths are considered the most critical aspects in the scale-up of microalgal culture. Several studies have investigated these features, resulting in a substantial body of literature that analyzes the [...] Read more.

The distribution of light within a microalgal culture and the choice of the best wavelengths are considered the most critical aspects in the scale-up of microalgal culture. Several studies have investigated these features, resulting in a substantial body of literature that analyzes the effects in terms of an increase in biomass production or shift in its composition. This work addresses two types of light quality adjustments: the application of flashing light and shifts in light wavelength. The effects on microalgal culture are examined. Later, the application of these light features to photobioreactor design is described. Specifically, three kinds of photobioreactors are examined: (1) reactors designed to minimize light gradients, (2) reactors where the geometry produces a flashing light effect on the cells and (3) reactors that use filters to obtain a shift in the sunlight wavelength. The results showed that both the effect of flashing lights and wavelength shift strongly depends on various parameters such as the alga taken into consideration, the light intensity, the agitation type, growth medium, light intensity and temperature and, regarding the flashing light also, the frequency and the duty cycle. Despite all these specific differences, this work aims to resume and provide specific instruments for choosing operational parameters in microalgal cultivation and in photobioreactor design to achieve targeted outcomes, such as an increase in biomass production or in high-value compound accumulation. Full article

(This article belongs to the Special Issue Bioreactor Design and Optimization Process)

► Show Figures

Figure 1

15 pages, 2715 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Influence of Effluent Quality Parameters on Daphnia spp. Overgrowth in an Urban Wastewater Treatment Plant: A Multiyear Case Study Analysis

by Pedro Esperanço, Rômulo Egito, Verónica Oliveira, António Luís Amaral and Carla Rodrigues

Processes 2025, 13(4), 1164; https://doi.org/10.3390/pr13041164 - 11 Apr 2025

Viewed by 813

Abstract

Wastewater treatment plants (WWTPs) play a crucial role in treating sewage, which undergoes multiple treatment stages to ensure a safe treated effluent. However, any interference during these stages can compromise the final effluent quality. Such is the case of the overgrowth of the [...] Read more.

Wastewater treatment plants (WWTPs) play a crucial role in treating sewage, which undergoes multiple treatment stages to ensure a safe treated effluent. However, any interference during these stages can compromise the final effluent quality. Such is the case of the overgrowth of the microcrustacean Daphnia spp., known to inhabit WWTPs, but with its presence in the decantation stage negatively impacting effluent clarification and further disinfection. This study aimed to evaluate how the effluent quality parameters influence the occurrence of Daphnia spp. in the secondary decanter of a WWTP. Wastewater monitoring data collected from 2017 to 2022 were analyzed. Firstly, as the COVID-19 pandemic occurred during the studied period, it was assessed whether the quality and load of the raw wastewater changed. Subsequently, an analysis was carried out using multivariate statistical methods for all the steps of WWTP. Comparing the periods before and during the pandemic, the raw wastewater volume decreased by 19.58%, and the BOD, COD, and TSS decreased by 37.78%, 16.86%, and 35.75%, respectively. These were the parameters affected the most. The statistical analysis revealed correlations between the presence of Daphnia spp. and specific effluent quality parameters, including raw wastewater BOD values below 500 mg L⁻¹, treated effluent BOD values below 13 mg L⁻¹, and pH levels exceeding 7.3. Additionally, BOD and pH were highlighted as critical parameters influencing their presence or absence. Full article

(This article belongs to the Special Issue Advanced Water Monitoring and Treatment Technologies)

► Show Figures

Figure 1

28 pages, 6411 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Numerical Study of Aerodynamic Drag Reduction and Heat Transfer Enhancement Using an Inclined Partition for Electronic Component Cooling

by Youssef Admi, Abdelilah Makaoui, Mohammed Amine Moussaoui and Ahmed Mezrhab

Processes 2025, 13(4), 1137; https://doi.org/10.3390/pr13041137 - 10 Apr 2025

Viewed by 483

Abstract

This study presents a numerical investigation of fluid flow around a heated rectangular cylinder controlled by an inclined partition, aiming to suppress vortex shedding, reduce aerodynamic drag, and enhance thermal exchange. The double multiple relaxation time lattice Boltzmann method (DMRT-LBM) is employed to [...] Read more.

This study presents a numerical investigation of fluid flow around a heated rectangular cylinder controlled by an inclined partition, aiming to suppress vortex shedding, reduce aerodynamic drag, and enhance thermal exchange. The double multiple relaxation time lattice Boltzmann method (DMRT-LBM) is employed to investigate the influence of Reynolds number variations and partition positions on the aerodynamic and thermal characteristics of the system. The results reveal the presence of three distinct thermal regimes depending on the Reynolds number. Increasing the Reynolds number intensifies thermal vortex shedding, thereby improving heat exchange efficiency. Moreover, a higher Reynolds number leads to a greater reduction in the drag coefficient, reaching

125.41 %

for

R e = 250

. Additionally, improvements in thermal performance were quantified, with Nusselt number enhancements of

29.47 %

for

R e = 100

,

55.55 %

for

R e = 150, 74.78 %

for

R e = 200

, and

82.87 %

for

R e = 250

. The influence of partition positioning g on the aerodynamic performance was also examined at

R e = 150

, revealing that increasing the spacing g generally leads to a rise in the drag coefficient, thereby reducing the percentage of drag reduction. However, the optimal configuration was identified at

g = 2 d

, where the maximum drag coefficient reduction reached

130.97 %

. In contrast, the impact of g on the thermal performance was examined for

R e = 100, 150,

and

200

, revealing a significant heat transfer improvements on the top and bottom faces: reaching up to

99.47 %

on the top face for

R e = 200

at

g = 3 d

. Nevertheless, for all Reynolds numbers and partition placements, a decrease in heat transfer was observed on the front face due to the partition shielding it from the incoming flow. These findings underscore the effectiveness of an inclined partition in enhancing both the thermal and aerodynamic performance of a rectangular component. This approach holds strong potential for various industrial applications, particularly in aeronautics, where similar control surfaces are used to minimize drag, as well as in heat exchangers and electronic cooling systems where optimizing heat dissipation is crucial for performance and energy efficiency. Full article

(This article belongs to the Special Issue Applications of Nanofluids and Nano-PCMs in Heat Transfer)

► Show Figures

Figure 1

17 pages, 2645 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Mathematical Modeling and Dynamic Simulation of a Tower Reactor for Intensified Ethanol Fermentation with Immobilized Yeasts and Simultaneous Gas Removal

by Dile Stremel, Valéria Pulitano and Samuel Oliveira

Processes 2025, 13(4), 1122; https://doi.org/10.3390/pr13041122 - 8 Apr 2025

Viewed by 596

Abstract

A mathematical model was developed for the dynamic and static simulation of a continuous ethanol production process in a tower bioreactor packed with yeast cells immobilized in citrus pectin gel. To avoid accumulation of CO₂ gas during the bioprocess, a vertical fixed [...] Read more.

A mathematical model was developed for the dynamic and static simulation of a continuous ethanol production process in a tower bioreactor packed with yeast cells immobilized in citrus pectin gel. To avoid accumulation of CO₂ gas during the bioprocess, a vertical fixed bed bioreactor with a working volume of 0.245 L, divided into four stages and equipped with external gas–liquid separators was used. The performance of the bioreactor was evaluated through continuous fermentations using feed medium (sugarcane juice) with substrate concentrations of 161.4 and 312.5 g/L, temperature of 30 °C, pH 4.0 and hydraulic residence times of 5 and 6 h. The developed mathematical model takes into account mass flow by convection and dispersion axial, external and internal mass transfer to/within particle, Contois kinetics for cell growth with inhibition terms, cell death, and substrate consumption for cell maintenance. The partial differential equations regarding cell, substrate and product mass balances in the solid and fluid phase were solved by numerical methods. The calculated profiles of state variables in the fluid phase agreed satisfactorily with the experimental data. The diffusional resistances within particles concerning the substrate consumption rate were not significant, resulting in calculated values of the effectiveness factor close to one. Full article

(This article belongs to the Special Issue Process Intensification in Chemical Reaction Engineering (2nd Edition))

► Show Figures

Figure 1

25 pages, 6699 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Optimization of ORC-Based Micro-CHP Systems: An Experimental and Control-Oriented Study

by Márcio Santos, Jorge André, Ricardo Mendes and José B. Ribeiro

Processes 2025, 13(4), 1104; https://doi.org/10.3390/pr13041104 - 7 Apr 2025

Cited by 1 | Viewed by 932

Abstract

This study presents an experimental and numerical investigation into the performance and control optimization of an Organic Rankine Cycle (ORC)-based micro-combined heat and power (micro-CHP) system. A steady-state, off-design, charge-sensitive model is developed to design a control strategy for an ORC micro-CHP combi-boiler, [...] Read more.

This study presents an experimental and numerical investigation into the performance and control optimization of an Organic Rankine Cycle (ORC)-based micro-combined heat and power (micro-CHP) system. A steady-state, off-design, charge-sensitive model is developed to design a control strategy for an ORC micro-CHP combi-boiler, aiming to efficiently meet real-time domestic hot water demands (up to 40 °C and 35 kW) while generating up to 2 kW of electricity. The system utilizes a natural gas burner to evaporate the working fluid (R245fa), with combustion heat power, volumetric pump speed, and expander speed as control variables. Experimental and numerical evaluations generate steady-state control maps to identify optimal operating regions. A PID-based dynamic control strategy is then developed to stabilize operation during start-ups and user demand variations. The results confirm that the strategy delivers hot water within 1.5 min in simple boiler mode and 3 min in cogeneration mode while improving electricity generation stability and outperforming manual control. The findings demonstrate that integrating steady-state modeling with optimized control enhances the performance, responsiveness, and efficiency of ORC-based micro-CHP systems, making them a viable alternative for residential energy solutions. Full article

(This article belongs to the Special Issue Modeling, Simulation and Control of Industrial Processes)

► Show Figures

Figure 1

21 pages, 7166 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Surrogate Modeling of Hydrogen-Enriched Combustion Using Autoencoder-Based Dimensionality Reduction

by Lanfei Zhang, Xu Chu, Siyu Ding, Mingshuo Zhou, Chenxu Ni and Xingjian Wang

Processes 2025, 13(4), 1093; https://doi.org/10.3390/pr13041093 - 5 Apr 2025

Viewed by 664

Abstract

Deep learning-based surrogate models have received wide attention for efficient and cost-effective predictions of fluid flows and combustion, while their hyperparameter settings often lack generalizable guidelines. This study examines two different types of surrogate models, convolutional autoencoder (CAE)-based reduced order models (ROMs) and [...] Read more.

Deep learning-based surrogate models have received wide attention for efficient and cost-effective predictions of fluid flows and combustion, while their hyperparameter settings often lack generalizable guidelines. This study examines two different types of surrogate models, convolutional autoencoder (CAE)-based reduced order models (ROMs) and fully connected autoencoder (FCAE)-based ROMs, for emulating hydrogen-enriched combustion from a triple-coaxial nozzle jet. The performances of these ROMs are discussed in detail, with an emphasis on key hyperparameters, including the number of network layers in the encoder (l), latent vector dimensionality (dim), and convolutional stride (s). The results indicate that a larger l is essential for capturing features in strongly nonlinear flowfields, whereas a smaller l is more effective for less nonlinear distributions, as additional layers may cause overfitting. Specifically, when employing CAE-based ROMs to predict the spatial distribution for H₂ (

X_{H_{2}}

) with weak nonlinearity, the reconstruction absolute average relative deviation (AARD) from the two-layer model was marginally higher than that of three- and four-layer models, whereas the prediction AARD was approximately 5% lower. A smaller dim yields better performance in weakly nonlinear flowfields but may increase local errors in some cases due to excessive feature compression. A CAE-based ROM with a dim = 10 achieved a notably lower AARD of 4.01% for

X_{H_{2}}

prediction. A smaller s may enhance the spatial resolution yet raise computational costs. Under identical hyperparameters, the CAE-based ROM outperformed the FCAE-based ROM in both cost-effectiveness and accuracy, achieving a 35 times faster training speed and lower absolute average relative deviation in prediction. These findings provide important guidelines for hyperparameter selection in training autoencoder (AE)-based ROMs for hydrogen-enriched combustion and other similar engineering design problems. Full article

(This article belongs to the Special Issue Modeling, Simulation and Control of Industrial Processes)

► Show Figures

Figure 1

21 pages, 10710 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Esterification of Glycerol and Rosin Catalyzed by Irganox 1425: A Kinetic Comparison to the Thermal Process

by Jorge García Montalvo, Natalia Robles-Anda, Felix García-Ochoa, M. Esther Gallardo and Miguel Ladero

Processes 2025, 13(4), 1096; https://doi.org/10.3390/pr13041096 - 5 Apr 2025

Viewed by 739

Abstract

Rosin is a biomass-based chemical raw material employed in multiple industries: paper, polymers, coatings, adhesives, and more, while glycerol production has experienced a notable increment in recent decades due to it being an unavoidable by-product of the biodiesel industry. Rosin polyol esters are [...] Read more.

Rosin is a biomass-based chemical raw material employed in multiple industries: paper, polymers, coatings, adhesives, and more, while glycerol production has experienced a notable increment in recent decades due to it being an unavoidable by-product of the biodiesel industry. Rosin polyol esters are of high interest, and a potential route for the valorization of glycerol. In this work, we compare in detail the esterification routes of rosin triglycerides via classical, industrial thermal processes at 260–280 °C and similar processes catalyzed by Irganox 1425, a high-molecular-weight, multifunctional, phenolic, primary antioxidant produced by BASF and usually in rosin processes. Its chemical name is calcium bis(ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate). To this end, a novel RP-HPLC method provided us with a detailed description of the compositional evolution of the reacting media. These data have been the basis of a non-linear kinetic modeling procedure where we applied non-linear regression and numerical integration algorithms to determine the network of chemical reactions and the kinetic model of the rosin–glycerol esterification process. Furthermore, the comparison of such kinetic models and their parameters allows us to understand the kinetic effect of the addition of the homogeneous catalyst. The effect of Irganox 1425 results in a notable enhancement of the reaction rates, thus allowing for operation at lower temperatures and a reduction in side reactions as decarboxylation. Full article

(This article belongs to the Special Issue Processes in Biofuel Production and Biomass Valorization)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI