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Sustain. Chem., Volume 6, Issue 2 (June 2025) – 7 articles

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This review explores the role of physical pretreatment methods in improving the enzymatic conversion of lignocellulosic biomass into fermentable sugars. Key techniques, such as mechanical comminution, irradiation (ultrasound, microwave, gamma rays, and electron beam), extrusion, and pulsed electric field, are critically analyzed in regards to their mechanisms, energy efficiency, and scalability. Particular emphasis is placed on the structural modifications induced by each method and their impact on hydrolysis performance. By comparing the advantages, limitations, and industrial applicability of each approach, this study provides strategic insights supporting the optimization of pretreatment selection based on biomass characteristics and processing objectives. View this paper
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41 pages, 7178 KiB  
Review
A Review of the Molecular Aggregation of Small-Molecule Anion Sensors for Environmental Contaminates in Aqueous Media
by Mallory E. Thomas and Alistair J. Lees
Sustain. Chem. 2025, 6(2), 17; https://doi.org/10.3390/suschem6020017 - 14 Jun 2025
Viewed by 1334
Abstract
A primary challenge in the further development of anion sensors in real water samples of environmental concern is the need for highly water-soluble compounds that are able to detect low concentrations of analytes. Small-molecule sensors can mitigate solubility constraints and highly aromatic or [...] Read more.
A primary challenge in the further development of anion sensors in real water samples of environmental concern is the need for highly water-soluble compounds that are able to detect low concentrations of analytes. Small-molecule sensors can mitigate solubility constraints and highly aromatic or conjugated systems may provide a new way to recognize target analytes with high sensitivity and/or selectivity. Organic aggregates that have the ability to form large frameworks can exhibit aggregated-induced emissions to detect target analytes, and their coagulation can provide enhanced detection via colorimetric or fluorescent measurements. This review aims to draw attention to the emerging area of small-molecule organic chemosensors that utilize aggregation to detect environmentally detrimental anions in an aqueous solution. A number of mechanisms of interaction for anion recognition are recognized and discussed here, including electrostatic interactions, covalent bond formation, hydrophobic interactions, and even complexation. Full article
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36 pages, 1130 KiB  
Review
The Need for Change: A Roadmap for the Sustainable Transformation of the Chemical Industry
by Klaus Günter Steinhäuser and Markus Große Ophoff
Sustain. Chem. 2025, 6(2), 16; https://doi.org/10.3390/suschem6020016 - 10 Jun 2025
Viewed by 848
Abstract
The chemical industry faces major challenges worldwide. Since 1950, production has increased 50-fold and is projected to continue growing, particularly in Asia. It is one of the most energy- and resource-intensive industries, contributing significantly to greenhouse gas emissions and the depletion of finite [...] Read more.
The chemical industry faces major challenges worldwide. Since 1950, production has increased 50-fold and is projected to continue growing, particularly in Asia. It is one of the most energy- and resource-intensive industries, contributing significantly to greenhouse gas emissions and the depletion of finite resources. This development exceeds planetary boundaries and calls for a sustainable transformation of the industry. The key transformation areas are as follows: (1) Non-Fossil Energy Supply: The industry must transition away from fossil fuels. Renewable electricity can replace natural gas, while green hydrogen can be used for high-temperature processes. (2) Circularity: Chemical production remains largely linear, with most products ending up as waste. Sustainable product design and improved recycling processes are crucial. (3) Non-Fossil Feedstock: To achieve greenhouse gas neutrality, oil, gas, and coal must be replaced by recycling plastics, renewable biomaterials, or CO2-based processes. (4) Sustainable Chemical Production: Energy and resource savings can be achieved through advancements like catalysis, biotechnology, microreactors, and new separation techniques. (5) Sustainable Chemical Products: Chemicals should be designed to be “Safe and Sustainable by Design” (SSbD), meaning they should not have hazardous properties unless essential to their function. (6) Sufficiency: Beyond efficiency and circularity, reducing overall material flows is essential to stay within planetary boundaries. This shift requires political, economic, and societal efforts. Achieving greenhouse gas neutrality in Europe by 2050 demands swift and decisive action from industry, governments, and society. The speed of transformation is currently too slow to reach this goal. Science can drive innovation, but international agreements are necessary to establish a binding framework for action. Full article
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20 pages, 921 KiB  
Article
Teaching the Nature of Science Through Biodiesel Synthesis from Waste Cooking Oil: A Literature Review with Experimental Insights
by Juan Peña-Martínez, Jessica Beltrán-Martínez, Ana Cano-Ortiz and Noelia Rosales-Conrado
Sustain. Chem. 2025, 6(2), 15; https://doi.org/10.3390/suschem6020015 - 19 May 2025
Viewed by 544
Abstract
This work reviews the use of biodiesel synthesis experiments in science education, emphasising their potential for explicit nature of science (NOS) teaching. Through a literature review and experimental insights, it highlights how transesterification of waste cooking oil (WCO) with a basic catalyst can [...] Read more.
This work reviews the use of biodiesel synthesis experiments in science education, emphasising their potential for explicit nature of science (NOS) teaching. Through a literature review and experimental insights, it highlights how transesterification of waste cooking oil (WCO) with a basic catalyst can serve as an educational tool. While biodiesel reaction conditions are well-documented, this study presents them in a pedagogical context. Simple viscosity and density measurements illustrate empirical analysis, while a design of experiments (DoE) approach using a Hadamard matrix introduces systematic optimisation and scientific reasoning. By integrating biodiesel synthesis with explicit NOS instruction, this work provides educators with a framework to foster critical thinking and a deeper understanding of scientific inquiry. Additionally, this approach aligns with green chemistry principles and resource efficiency, reinforcing the broader relevance of sustainable chemistry. Full article
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14 pages, 1519 KiB  
Article
Antiviral Activity of Rambutan Peel Polyphenols Obtained Using Green Extraction Technology and Solvents
by Christian Hernández-Hernández, Luis E. Estrada-Gil, Sonia A. Lozano-Sepúlveda, Ana M. Rivas-Estilla, Mayela Govea-Salas, Jesús Morlett-Chávez, Cristóbal N. Aguilar and Juan A. Ascacio-Valdés
Sustain. Chem. 2025, 6(2), 14; https://doi.org/10.3390/suschem6020014 - 29 Apr 2025
Viewed by 667
Abstract
Rambutan peel is a great source of bioactive compounds, the same that, over the years, has been extracted using conventional technologies which have been proven to be harmful to the environment and potentially toxic to human beings. This study aimed to extract the [...] Read more.
Rambutan peel is a great source of bioactive compounds, the same that, over the years, has been extracted using conventional technologies which have been proven to be harmful to the environment and potentially toxic to human beings. This study aimed to extract the same compounds using a hybridization of ultrasound/microwave extraction. The results were promising, as a total of 378.48 ± 9.19 mg/g of polyphenols were recovered from this procedure, and the most important molecules (geraniin, corilagin, and ellagic acid) were identified, giving this much more relevance. Furthermore, treatment with rambutan peel extract recovered with green technologies significantly reduced cell viability in HCV-infected liver cells. Notably, higher concentrations (4000 and 5000 ppm) led to more pronounced cell death in huh7 cells. The treatment also led to a significant reduction in viral protein and RNA expression in HCV-infected cells. These findings suggest that rambutan peel extract obtained from the combination of ultrasound and microwave extraction, particularly the ellagitannins present, have potential antiviral properties. Further research is needed to explore its mechanism of action and its potential as a therapeutic agent for Hepatitis C. Full article
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36 pages, 971 KiB  
Review
Physical Pretreatments of Lignocellulosic Biomass for Fermentable Sugar Production
by Damázio Borba Sant’Ana Júnior, Maikon Kelbert, Pedro Henrique Hermes de Araújo and Cristiano José de Andrade
Sustain. Chem. 2025, 6(2), 13; https://doi.org/10.3390/suschem6020013 - 14 Apr 2025
Viewed by 1412
Abstract
Physical pretreatments play a crucial role in reducing the recalcitrance of lignocellulosic biomass, facilitating its conversion into fermentable sugars for bioenergy and chemical applications. This study critically reviews physical pretreatment approaches, including mechanical comminution, irradiation (ultrasound, microwave, gamma rays, and electron beam), extrusion, [...] Read more.
Physical pretreatments play a crucial role in reducing the recalcitrance of lignocellulosic biomass, facilitating its conversion into fermentable sugars for bioenergy and chemical applications. This study critically reviews physical pretreatment approaches, including mechanical comminution, irradiation (ultrasound, microwave, gamma rays, and electron beam), extrusion, and pulsed electric field. The discussion covers the mechanisms of action, operational parameters, energy efficiency, scalability challenges, and associated costs. Methods such as ultrasound and microwave induce structural changes that enhance enzymatic accessibility, while extrusion combines thermal and mechanical forces to optimize hydrolysis. Mechanical comminution is most effective during short periods and when combined with other techniques to overcome limitations such as high energy consumption. Innovative approaches, such as pulsed electric fields, show significant potential but face challenges in large-scale implementation. This study provides technical and strategic insights into developing more effective physical pretreatments aligned with economic feasibility and industrial sustainability. Full article
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16 pages, 1536 KiB  
Article
Assessment of Co-Pyrolysis of Polypropylene with Triacylglycerol-Based Waste Biomass to Obtain Sustainable Hydrocarbons
by Isaac de Carvalho Guimarães, Mirele Santana de Sá, Tarcísio Martins and Alberto Wisniewski, Jr.
Sustain. Chem. 2025, 6(2), 12; https://doi.org/10.3390/suschem6020012 - 8 Apr 2025
Viewed by 954
Abstract
Sustainable hydrocarbons are one of the main methods of decreasing the use of fossil fuels and derivatives, contributing to the mitigation of environmental impacts and greenhouse gas emissions. Circular economic concepts focus on reusing waste by converting it into new products, which are [...] Read more.
Sustainable hydrocarbons are one of the main methods of decreasing the use of fossil fuels and derivatives, contributing to the mitigation of environmental impacts and greenhouse gas emissions. Circular economic concepts focus on reusing waste by converting it into new products, which are then input again into industrial production lines, thus decreasing the necessity of fossils. Polypropylene-based plastic waste can be depolymerized into smaller chemical chains, producing a liquid phase rich in hydrocarbons. In the same way, triacylglycerol-based waste biomasses can also be converted into renewable hydrocarbons. Our research studied the co-processing of polypropylene (PP) and cottonseed oil dreg (BASOs) waste from the biodiesel industry using a micropyrolysis system at 550 °C, previously validated to predict the scale-up of the process. PP showed the production of alkanes and alkenes, while BASOs also produced carboxylic acids in addition to the PP products. The main impacts were observed in the conversion yields, reaching the highest values of pyrolytic liquid (64%), gas (14%), and solid product (13%) compared to the co-processing mixture of BASO:PP (1:2). Also, in this mixture, the production of carboxylic acids decreased to the lowest value (~10%), improving the conversion to sustainable hydrocarbons. Full article
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13 pages, 1477 KiB  
Article
Cultivation of Chlorella sp. in a Closed System Using Mining Wastewater and Simulated Flue Gas: Biomass Production and CO2 Fixation Potential
by Thiago J. T. Cruz, Guilherme Q. Calixto, Fabiana R. de A. Câmara, Dárlio I. A. Teixeira, Renata M. Braga and Sibele B. C. Pergher
Sustain. Chem. 2025, 6(2), 11; https://doi.org/10.3390/suschem6020011 - 31 Mar 2025
Viewed by 558
Abstract
Chlorella sp. was cultivated in a closed system using PET bottles (5 L) and with the continuous injection of air and commercial gas (98% CO2) and in simulated conditions (15% CO2, 73% N2, and 12% O2 [...] Read more.
Chlorella sp. was cultivated in a closed system using PET bottles (5 L) and with the continuous injection of air and commercial gas (98% CO2) and in simulated conditions (15% CO2, 73% N2, and 12% O2). The culture medium was prepared using well water and mining wastewater, the cultivation period occurred in a 10-day cycle, and the cell growth curves were evaluated through cell counting using a Neubauer chamber. The cultivation was carried out under the following conditions: temperature at 22 °C to 25 °C; aeration rate with commercial and simulated CO2 gas at 0.01 vvm; and synthetic air containing 0.042% CO2. The dry biomass productivity was 0.81 g·L−1·day−1 and the maximum CO2 fixation rate was 0.90 g·L−1·day−1 when the microalgae were cultivated with a continuous flow of simulated waste gas and a culture medium composed of wastewater. The percentages of macromolecules obtained in the biomass cultivated in wastewater reached 20.95%, 26.48%, and 9.3% for lipids, proteins, and carbohydrates, respectively. Full article
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