Sustainable Chemistry

Iodine is an essential element for the synthesis of thyroid hormones. Iodine deficiency leads to a range of health consequences known as iodine deficiency disorders. To assess the iodine nutritional status of a population, urinary iodine (UI) is typically measured. This work introduces a novel and simple analytical method for determining UI using silver triangular nanoplates (AgTNPs) after interfering substances are removed via solid-phase extraction (SPE). The AgTNPs were synthesized and characterized using Transmission Electron Microscopy, UV–vis spectroscopy, and zeta potential measurements. The limit of detection of iodide of the AgTNPs assessed spectrophotometrically was 35.78 µg I⁻/L. However, urine samples interfered with the colorimetric reaction. Thus, an SPE methodology was developed and optimized to eliminate urine interferents that hinder AgTNP performance. A logistic regression analysis was conducted to validate the combined application of SPE and AgTNPs for the qualitative determination of UI. This work demonstrated that the developed SPE methodology eliminates these interferents and extracts iodide from the sample, allowing the accurate determination of UI using AgTNPs. This reliable sample preparation method was then used on actual human urine samples to accurately identify UI deficiency levels. The proposed methodology offers an effective and environmentally friendly approach for monitoring iodine status, without requiring highly complex equipment. Full article

This review sheds some light on the emerging niche of the reuse of spent adsorbents in electrochemical devices. Reuse and repurposing extend the adsorbent’s life cycle, remove the need for long-term storage, and generate additional value, making it a highly eco-friendly process. Main adsorbent-type materials are overviewed, emphasising desired properties for initial adsorption and subsequent conversion to electroactive material step. The effects of the most frequent regeneration procedures are compared to highlight their strengths and shortcomings. The latest efforts of repurposing and reuse in supercapacitors, fuel cells, and batteries are analysed. Reuse in supercapacitors is dominated by materials that, after a regeneration step, lead to materials with high surface area and good pore structure and is mainly based on the conversion of organic adsorbents to some form of conductive carbon adlayer. Additionally, metal/metal-oxide and layered-double hydroxides are also being developed, but predominantly towards fuel cell and battery electrodes with respectable oxygen reduction characteristics and significant capacities, respectively. Repurposed adsorbents are being adopted for peroxide generation as well as direct methanol fuel cells. The work puts forward electrochemical devices as a valuable avenue for spent adsorbents and as a puzzle piece towards a greener and more sustainable future. Full article

With increasing concerns about climate change and the depletion of fossil fuels, hemicellulose sugars from lignocellulosic biomass are gaining attention as sustainable feedstocks for producing biofuels and valuable chemicals. In this study, the extraction of hemicellulose sugars from corncob biomass was performed using hydrothermal pretreatment. Response Surface Methodology (RSM) with the Box–Behnken Design (BBD) was employed to optimize different parameters. The tested parameters included the corncob-to-water ratio (0.5:10, 1.5:10), time (30 to 90 min), and temperature (150 to 170 °C), to achieve the highest sugar yields (xylose, arabinose, and total sugars). The ANOVA results for the full quadratic polynomial model, which evaluates the effects of the three variables on xylose yield, indicate that the model is highly significant and provides a good fit to the data. This was evidenced by the minimal difference (0.003) between the predicted R² and the adjusted R². This study reports one of the highest recoveries of hemicellulosic sugars from corncobs and also evaluates degradation byproducts, offering a more efficient and comprehensive pretreatment approach that employs a lower temperature and a mild acid concentration (1%) compared with earlier research. The highest yields of xylose (103.49 mg/g), arabinose (26.75 mg/g), and total sugars (163.21 mg/g) were obtained at 160 °C and a corncob-to-water ratio of 0.5:10, after 90 min. Degradation products such as HMF and furfural in the hydrolysate were also analyzed by HPLC. The hydrolysate obtained from hydrothermal pretreatment contained oligomers that were converted into monomers through 1% H₂SO₄ hydrolysis. The highest yields after the acidic hydrolysis were 301.93 mg/g xylose, 46.96 mg/g arabinose, and 433.79 mg/g total sugars hydrolysis. Full article

This study investigates the potential of Pinus pinaster subsp. atlantica bark, a forestry by-product from northern Portugal, as a source of phenolic compounds with strong antioxidant properties. Microwave-assisted extraction (MAE) was used to optimize recovery, assessing the effects of solvent composition (water, ethanol, and 50:50 water–ethanol), extraction time (15 or 30 min), and temperature (90, 110, or 130 °C) using a one-variable-at-a-time approach. High-Performance Liquid Chromatography (HPLC) profiling characterized the polyphenol composition. The results showed that solvent choice strongly influenced extract composition and bioactivity, with hydroethanolic and ethanolic extracts exhibiting the highest antioxidant activities in DPPH, ABTS, and ORAC assays. Optimal conditions—50:50 water–ethanol, 130 °C, 15 min—yielded 11.13% (w/w) extract, 3.10 mg GAE/mL total phenolics, and 2.01 mg CE/mL condensed tannins, comparable to commercial extracts such as Pycnogenol^®. MAE proved effective, rapid, and solvent-efficient, enhancing phenolic recovery without degrading extract quality. These findings highlight the potential of P. pinaster bark extracts for biomedical, nutraceutical, and cosmetic applications, supporting the sustainable valorization of forestry residues and aligning with circular economy principles. Full article

This review highlights recent advances in the use of nutshell-derived materials, including peanut, walnut, and other lignocellulosic shell wastes, as reinforcers in polymer composites. The focus is placed on evaluating how the incorporation of nutshell fillers influences the mechanical and thermal properties of various polymer matrices. Key findings across multiple studies show that nutshell reinforcement can significantly enhance tensile strength, modulus, thermal stability, and biodegradability, depending on filler concentration, particle size, and surface treatment. The review also discusses the sustainability and economic benefits of using agricultural waste as a functional additive, offering insights into the design of low-cost, eco-friendly polymer composites for packaging, construction, and environmental applications. Full article

Facing energy and environmental issues is recognized globally as one of the major challenges for sustainable development, to which sustainable chemistry can make significant contributions. Strontium ferrate-based materials belong to a little-known class of perovskite-type compounds in which iron is primarily stabilized in the unusual 4+ oxidation state, although some Fe³⁺ is often present, depending on the synthesis and processing conditions and the type and amount of dopant. When doped with cerium at the Sr site, the SrFeO_3−δ cubic structure is stabilized, more oxygen vacancies form and the Fe⁴⁺/Fe³⁺ redox couple plays a key role in its functional properties. Alone or combined with other materials, Ce-doped strontium ferrates can be successfully applied to wastewater treatment. Specific doping at the Fe site enhances their electronic conductivity for use as electrodes in solid oxide fuel cells and electrolyzers. Their oxygen storage capacity and oxygen mobility are also exploited in chemical looping reactions. The main limitations of these materials are SrCO₃ formation, especially at the surface; their low surface area and porosity; and cation leaching at acidic pH values. However, these limitations can be partially addressed through careful selection of synthesis, processing and testing conditions. This review highlights the high versatility and efficiency of cerium-doped strontium ferrates for energy and environmental applications, both at low and high temperatures. The main literature on these compounds is reviewed to highlight the impact of their key properties and synthesis and processing parameters on their applicability as sustainable thermocatalysts, electrocatalysts, oxygen carriers and sensors. Full article

Natural dyes and pigments are gaining importance as a sustainable alternative to synthetic dyes. Sourced from renewable materials, they are known for their biodegradable and non-toxic properties, offering a diverse range of color profiles and applications across industries such as textiles, cosmetics, food, and pharmaceuticals. This manuscript discusses various aspects of natural dyes and pigments (derived from plants and microbes), including anthocyanins, flavonoids, carotenoids, lactones, and chlorophyll. Furthermore, it highlights the polyphenolic nature of these compounds, which is responsible for their antioxidant activity and contributes to their anticancer, antibacterial, antifungal, antiprotozoal, and immunomodulatory effects. However, natural dyes are often categorized as pigments rather than dyes due to their limited solubility, a consequence of their molecular characteristics. Consequently, this manuscript provides a detailed discussion of key structural challenges associated with natural dyes and pigments, including thermal decomposition, photodegradation, photoisomerization, cross-reactivity, and pH sensitivity. Due to these limitations, natural dyes are currently used in relatively limited applications, primarily in the food industry, and, to lesser extent, in textiles and coatings. Nevertheless, with ongoing research and technological innovations, natural dyes present a viable alternative to synthetic dyes, promoting a more sustainable and environmentally conscious future. Full article

2,5-bis(hydroxymethy)lfuran (BHMF), a renewable compound with extensive industrial applications, can be obtained by selective hydrogenation of the C=O group of 5-hydroxymethylfurfural (HMF), a platform molecule derived from lignocellulosic biomass. In this work, we perform kinetic modeling of the selective liquid-phase hydrogenation of HMF to BHMF over a Cu/SiO₂ catalyst prepared by precipitation–deposition (PD) at a constant pH. Physicochemical characterization, using different techniques, confirms that the Cu/SiO₂–PD catalyst is formed by copper metallic nanoparticles of 3–5 nm in size highly dispersed on the SiO₂ surface. Before the kinetic study, the Cu/SiO₂-PD catalyst was evaluated in three solvents: tetrahydrofuran (THF), 2-propanol (2-POH), and water. The pattern of catalytic activity and BHMF yield for the different solvents was THF > 2-POH > H₂O. In addition, selectivity to BHF was the highest in THF. Thus, THF was chosen for further kinetic study. Several experiments were carried out by varying the initial HMF concentration (C⁰_HMF) between 0.02 and 0.26 M and the hydrogen pressure (P_H2) between 200 and 1500 kPa. In all experiments, BHMF selectivity was 97–99%. By pseudo-homogeneous modeling, an apparent reaction order with respect to HFM close to 1 was estimated for a C⁰_HMF between 0.02 M and 0.065 M, while when higher than 0.065 M, the apparent reaction order changed to 0. The apparent reaction order with respect to H₂ was nearly 0 when C⁰_HMF = 0.13 M, while for C⁰_HMF = 0.04 M, it was close to 1. The reaction orders estimated suggest that HMF is strongly absorbed on the catalyst surface, and thus total active site coverage is reached when the C⁰_HMF is higher than 0.065 M. Several Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were proposed, tested against experimental data, and statistically compared. The best fitting of the experimental data was obtained with an LHHW model that considered non-competitive H₂ and HMF chemisorption and strong chemisorption of reactant and product molecules on copper metallic active sites. This model predicts both the catalytic performance of Cu/SiO₂-PD and its deactivation during liquid-phase HMF hydrogenation. Full article

Dry Turkish oak (Quercus cerris) sawdust, untreated and treated with three activators, (H₃PO₄, NaOH and H₂O₂) was pyrolyzed under limited-oxygen conditions to obtain biochar samples. The electrochemical properties of these samples were tested and compared to the properties of several commercial carbon blacks. The electrochemical characterization was performed via cyclic voltammetry, analyzing the response toward two commonly used redox probes, [Fe(CN)₆]^3−/−4− and [Ru(NH₃)₆]^2+/3+. The influence of the scan rate on this response was investigated, and the resulting data were used to obtain the values of the heterogenous charge transfer constant, k₀. Higher k₀ values were observed for carbon blacks than for investigated biochar samples. The detection of 4-nitrophenol and heavy metal ions was used to assess the applicability of biochars for electroanalytical purposes. The response of untreated biochar was comparable with the response of Vulcan carbon black, which showed the best response of all analyzed carbon blacks. Full article

Biomorphic mineralization was employed to synthesize novel Mn–Ce and Mn–Co–Ce oxide fibers using commercial cotton as a biotemplate, aiming to assess their catalytic performance in diesel soot combustion and CO oxidation. Two synthesis protocols—one with and one without citric acid—were investigated. The inclusion of citric acid led to fibers with more uniform morphology, attributed to improved precursor distribution, although synthesis yields decreased for Co-containing systems. In soot combustion tests, Mn–Ce catalysts synthesized with citric acid outperformed their monometallic counterparts. While cobalt incorporation enhanced the mechanical robustness of the fibers, it did not significantly boost catalytic activity. Selected formulations were also evaluated for CO oxidation, with Mn–Co–Ce fibers achieving T₅₀ values in the 240–290 °C range, comparable to Co–Ce nanofibers reported in the literature. These results demonstrate that biomorphic fibers produced through a simple and sustainable route can offer competitive performance in soot and CO oxidation applications. Full article

The thermal modification of wood has emerged as a sustainable and effective method for enhancing the physical, chemical, and mechanical properties of wood without the use of harmful chemicals. This review summarizes the current state-of-the-art in thermal wood modification, focusing on the mechanisms of wood degradation during treatment and the resulting changes in the properties of the material. The benefits of thermal modification of wood include improved dimensional stability, increased resistance to biological decay, and improved durability, while potential risks such as reduced mechanical strength, color change, and higher costs of wood under certain conditions are also discussed. The review highlights recent advances in process optimization and evaluates the trade-offs between improved performance and possible structural drawbacks. Finally, future perspectives are outlined for sustainable applications of thermally modified wood in various industries. Emerging trends and future research directions in the field are identified, aiming to improve the performance and sustainability of thermally modified wood products in construction, furniture, and other industries. Full article

Volcanic ashes (VA) ejected by the Tajogaite Volcano were studied to determine their potential as pozzolanic materials for construction applications. A representative number of VA samples (15 in total) were collected from different geolocations and altitudes during and immediately after the volcanic eruption, in order to assess their reactivity as a function of position and environmental exposure. Various analytical techniques—XRD, FTIR, and SEM/EDX—were used to determine the initial microstructural composition of the VA samples. Additionally, saturated lime testing and the Frattini test were performed to evaluate their pozzolanic reactivity for use in historical mortars. The microstructural analyses revealed that the dominant mineral phases are aluminosilicates. The reactivity tests confirmed a good pozzolanic response, with the formation of C-A-S-H gels identified as the main hydration products at the studied curing times. Full article

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

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

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

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

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

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

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