Sustainable Chemistry

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

Twelve marine-derived fungal strains were evaluated for their ability to synthesize silver nanoparticles (AgNPs). Mycogenic AgNPs were preliminarily characterized using different techniques, and their antimicrobial activities were assessed. Penicillium citrinum IBCLP11 and Aspergillus niger IBCLP20 were selected for AgNPs’ synthesis optimization by varying parameters such as AgNO₃ concentration, biomass, agitation, temperature, and pH. AgNP_IBCLP11 and AgNP_IBCLP20 were able to inhibit the growth of Pseudomonas aeruginosa IPT322, Staphylococcus aureus IPT246, and Klebsiella pneumoniae IPT412 at concentrations of 25 μg/mL or higher. Aspergillus niger IPT295 and Aspergillus parasiticus IPT729 were the most sensitive to AgNP_IBCLP20. Further studies are needed to fully elucidate the effects of all parameters influencing mycogenic AgNPs synthesis. However, it is evident that maintaining optimal conditions, such as temperature and pH during agitation, is crucial for preventing undesirable reactions and ensuring nanoparticle stability. Full article

Zeolites are amongst the most extensively explored crystalline microporous materials because of their variable chemical composition, framework geometry, pore dimensions, and tunability. Due to their high surface area, adsorption selectivity, mechanical, biological, chemical, and thermal stability, these molecular sieves are widely used in adsorption, catalysis, ion exchange, and separation technologies. This short review highlights the notable progress achieved in leveraging the properties of zeolite materials for multiple applications, including gas separation and storage, adsorption, catalysis, chemical sensing, and biomedical applications. The aim is to emphasize their capabilities by showcasing important achievements that have driven research in this field toward new and unforeseen areas of material chemistry. Full article

Heavy metal contamination of water sources has emerged as a major global environmental concern, affecting both aquatic ecosystems and human health. Therefore, this study aims to remove hexavalent chromium from an aqueous solution utilizing activated carbon developed from Spathodea campanulata. Chemical treatment with H₃PO₄ followed by thermal activation was employed to enhance the adsorption capability of the precursor material. On the other hand, a full factorial design of 2⁴ including pH (3 and 9), contact time (30 and 60 min), initial chromium concentration (40 and 100 mg/L), and adsorbent dosage of 0.2 and 0.6 g/100 mL was used to optimize the batch-wise adsorption of hexavalent chromium. The characterization results showed that the prepared activated carbon is composed of various functional groups (FTIR), a high specific surface area of 1054 m²/g (BET), morphological cracks (Scanning Electron Microscopy), and a pH point of zero charge of 5.8. The maximum removal efficiency of 96.5% was recorded at optimum working conditions of pH 3, contact time of 60 min, adsorbent dosage of 0.6 g/100 mL, and initial chromium concentration of 40 mg/L. Additionally, kinetics and isotherm studies revealed that the pseudo-second-order model with R² of 0.98 and the Sips model with R² of 0.99 were found to fit the adsorption data better, suggesting homogenous surface and chemisorption. Overall, this research suggests that Spathodea campanulata could be a promising natural source for the development of adsorbents with potential applications in remediating chromium-saturated wastewater at an industrial scale. Full article

Lithium-ion batteries that use lithium iron phosphate (LiFePO₄) as the cathode material and carbon (graphite or MCMB) as the anode have gained significant attention due to their cost-effectiveness, low environmental impact, and strong safety profile. These advantages make them suitable for a wide range of applications including electric vehicles, stationary energy storage, and backup power systems. However, their adoption is hindered by a critical challenge: capacity degradation at elevated temperatures. This review systematically summarizes the corresponding modification strategies including surface modification of the anode and cathode as well as modification of the electrolyte, separator, binder, and collector. We further discuss the control of the charge state, early warning prevention, control of thermal runaway, and the rational application of ML and DFT to enhance the LFP/C high temperature cycling stability. Finally, in light of the current research challenges, promising research directions are presented, aiming at enhancing their performance and stability in such harsh thermal environments. Full article

This study addresses the environmental challenge of surfactant removal from wastewater, focusing on the increased surfactant use during the COVID-19 pandemic. Polymeric waste, specifically polyurethane (PU) and polyamide (PA), was repurposed for surfactant adsorption to mitigate these environmental impacts. Methods included preparing surfactant solutions of sodium linear alkylbenzene sulfonate (LAS) and dodecyl pyridinium chloride (DPC) and the mechanical processing of polymeric residues. PU and PA were characterized by FTIR-ATR and by the pH at the point of zero charge, which yielded pH = 8.0 for both polymers. The adsorption efficiency was optimized using a central composite face-centered design, varying pH, temperature, and time. The results indicated that PU and PA effectively adsorbed anionic and cationic surfactants, with specific conditions enhancing performance. From the optimized experimental conditions, four assays were carried out to evaluate the adsorption isotherms and kinetics. Among the fitted models, the SIPS model was the most representative, indicating a heterogeneous surface. Regarding LAS, the maximum adsorption capacity values were ~90 and 15 mg g⁻¹, respectively, for PU and PA. Considering the DPC surfactant, lower values were obtained (~36 mg g⁻¹ for PU and 16 mg g⁻¹ for PA). The results are satisfactory because the adsorbents used in this study were second-generation waste and were used without treatment or complex modifications. The study concluded that using polymeric waste for surfactant removal offers a sustainable solution, transforming waste management while addressing environmental contamination. This approach provides a method for reducing surfactant levels in wastewater and adds value to otherwise discarded materials, promoting a circular economy and sustainable waste reuse. Full article

Heavy metal pollution in water resources, particularly cadmium and lead, poses a significant environmental and public health challenge, requiring the development of sustainable, efficient, and cost-effective water treatment methods. Therefore, this study investigates the biosorption capabilities of natural (SN) and surfactant-modified (SM) guava seed biosorbents to remove Cd and Pb from aqueous solutions. Guava seeds, an agricultural waste material, were treated with hexadecyltrimethylammonium bromide (HDTMA-Br) to enhance their adsorption efficiency. The biosorbents were characterized by FTIR, SEM-EDS, and zeta potential analysis to explain the surface modifications and their influence on the adsorption mechanisms. Batch experiments were performed to evaluate the effects of pH, contact time, temperature, biosorbent dosage, and concentration on Cd and Pb removal efficiencies. Adsorption isotherm and kinetic data were analyzed using mathematical models to obtain the basic parameters of the systems under study. The results showed that SM exhibited superior adsorption capacities of 328 mg/g for Cd and 594 mg/g for Pb at 25 °C, significantly outperforming SN. The study analyzed the thermodynamic parameters of adsorption systems, revealing endothermic and exothermic properties for SN and SM. Functional groups like hydroxyl and carbonyl were crucial for metal ion binding. HDTMA-Br introduced active sites and enhanced surface charge interactions. Regeneration tests showed reusability, maintaining over 85% efficiency after four cycles. Guava seeds could be cost-effective and sustainable biosorbents for heavy metal removal. Full article

The incorporation of Ag nanoparticles onto BiVO₄ (a known H₂O oxidising photocatalyst) through magnetron sputtering to form a composite was studied. ICP-OES results showed that the loading of Ag on BiVO₄ was below 1% in all cases. UV-Vis DRS and CO₂-TPD analyses demonstrated that upon incorporation of Ag onto BiVO₄, an increase in the extent of visible light absorption and CO₂ adsorption was seen. TEM imaging showed the presence of Ag particles on the surface of larger BiVO₄ particles, while XRD analysis provided evidence for some doping of Ag into BiVO₄ lattices. The effect of the composite formation on the activity of the materials in the artificial photosynthesis reaction was significant. BiVO₄ alone produces negligible amounts of gaseous products. However, the Ag-sputtered composites produce both CO and CH₄, with a higher loading of Ag leading to higher levels of product formation. This reactivity is ascribed to the generation of a heterojunction in the composite material. It is suggested that the generation of holes in BiVO₄ following photon absorption is used to provide protons (from H₂O oxidation), and the decay of an SPR response on the Ag NPs provides hot electrons, which together with the protons reduce CO₂ to produce CH₄, CO, and adsorbed hydrocarbonaceous species. Full article

The perovskite oxides CaMnO_3-δ, Ca_0.5Sr_0.5MnO_3-δ, and SrMnO_3-δ were synthesized in air using a solid-state method, and their structural, electrical, and electrocatalytic properties were studied in relation to their oxygen evolution reaction (OER) performance. Iodometric titration showed δ values of 0.05, 0.05, and 0.0, respectively, indicating that Mn is predominantly in the 4+ oxidation state across all materials, consistent with prior reports. Detailed characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), iodometric titration, and variable-temperature conductivity measurements. Four-point probe DC measurements revealed that CaMnO_3-δ (δ = 0.05) has a semiconductive behavior over a temperature range from 25 °C to 300 °C, with its highest conductivity attributed to polaron activity. Cyclic voltammetry (CV) in 0.1 M KOH was employed to assess OER catalytic performance, which correlated with room-temperature conductivity. CaMnO_3-δ exhibited superior catalytic activity, followed by Ca_0.5Sr_0.5MnO_3-δ and SrMnO_3-δ, demonstrating that increased conductivity enhances OER performance. The conductivity trend, CaMnO_3-δ > Ca_0.5Sr_0.5MnO_3-δ > SrMnO_3-δ, aligns with OER activity, underscoring a direct link between electronic transport properties and catalytic efficiency within this series. Full article

This review explores both the positive and negative impacts of chemistry on society, focusing on the intersection between pharmaceutical, natural, and synthetic chemicals. On the one hand, drugs developed through medicinal chemistry have saved lives, improved people’s quality of life, and increased longevity. However, they also pose risks, including fatalities and environmental damage. Pharmaceutical chemistry has revolutionized medical practice by enabling the treatment and cure of fatal or debilitating diseases, significantly contributing to the rise in global life expectancy through the research and development of new bioactive substances. This article also highlights the harmful effects of toxic synthetic substances, which negatively impact human health and the environment, affecting plants, animals, air, water, soil, and food. Full article

The titanium dioxide (TiO₂) photocatalyst is an important semiconducting material that exhibits environmental purification functions when exposed to light. Elemental doping of TiO₂ is considered an important strategy to improve its photocatalytic activity. Herein, we have achieved the low-temperature, atmospheric-pressure synthesis of anatase TiO₂ particles with doping of 3d metals (Fe, Co, Ni and Cu) based on the liquid phase deposition technique. All products prepared by adding 3d metals were found to consist of TiO₂ crystals in the anatase phase with a fine protruding structure of about 40 nm on the surface, as was the case without the addition of metal ions. Iron and copper were observed to be incorporated at higher concentrations than cobalt and nickel, with an elemental addition of up to 4 at% and 1 at%, respectively, when 10 mM iron and copper nitrate were applied. Such doping efficiency could be explained by the difference in ionic radius and chemical stability. A narrowing of the optical band gap with doping elements was also observed, and it was found that optical sensitivity could be imparted down to the visible-light region of 2.4 eV (Fe: 4 at% addition). Furthermore, the 3d metal-doped TiO₂ demonstrated in this study was shown to exhibit photocatalytic methane degradation activity. The amount of methane degradation per unit area of the microparticles was twice as great when iron and copper were added, compared to the undoped counterpart. It has been demonstrated that the strategy of doping TiO₂ with 3d metal ions by low-temperature synthesis methods is effective in enhancing carrier dynamics and introducing surface active sites, thus increasing methane degradation activity. Full article

The well-being of the Earth and its inhabitants is compromised by the energy and climate crisis that has arisen from the prolonged and uncontrolled utilization of fossil fuels, which has caused a tremendous increase in anthropogenic CO₂ and a consistent depletion of natural energy resources [...] Full article

Brewer’s spent grains (BSG) are a by-product of the beer industry and can be used to produce biofuels. In this case, the objective of this study was to obtain reducing sugars from this biomass by subcritical water hydrolysis in a semi-continuous mode after steam explosion. Temperatures of 120–180 °C, reaction times of 1–5 min, and pressures of 15–25 MPa were used for the steam explosion without CO₂. Moistures of 10–50% (w/v), temperatures of 120–180 °C, reaction times of 1–5 min, and pressures of 15–25 MPa were used for the steam explosion with CO₂. Subcritical water hydrolysis of solid-exploded material was developed at 210 °C, 15 MPa, a solid/feed ratio of 16 g/g, and a flow rate of 20 mL/min. The characterization of BSG, reducing sugar yields, kinetic profiles, the composition of monosaccharides and furanic moieties, and the characterization of remaining solid by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were performed. For steam explosion with CO₂, the significant variables were the temperature and moisture, and the optimized conditions were moisture of 50% (w/v), 120 °C, pretreatment for 1 min, and 15 MPa, with a reducing sugars yield of 18.41 ± 1.02 g/100 g BSG. For steam explosion without CO₂, the significant variables were the time and temperature, and the optimized conditions were 120 °C, pretreatment for 1 min, and 15 MPa, with a reducing sugars yield of 17.05 ± 0.48 g/100 g BSG. The process was successful because the steam explosion ruptured the lignocellulosic matrix, and the subsequent process of subcritical water hydrolysis could dissociate the polymers into low-chain saccharides. Full article

Biochar, produced through the pyrolysis of biomass and green waste, offers significant potential as a soil amendment to enhance soil health and sustainability in agriculture. However, the current Measurement, Reporting, and Verification (MRV) systems for biochar predominantly focus on carbon credits/offsets, neglecting crucial aspects related to its usability and suitability as a soil amendment on agricultural fields. Through an examination of recent findings, this perspective explores the integration of geochemical tracers, functional group (hydroxyl, carboxyl, phenolic, lactonic, etc.) analysis, and nutrient dynamics into MRV procedures/systems to create a more comprehensive framework. By examining the applicability of these indicators, this paper identifies key gaps and proposes a more robust MRV approach. Such a system would not only facilitate better assessment of biochar’s agronomic benefits but also guide its optimal use in various soil types and agricultural practices. Full article

In this study, several professional cleaning products were analyzed for their impact on local air and sewage contamination. The products were first analyzed for their content of potentially harmful ingredients, their biodegradability, and the potential for the mobilization of hazardous substances from the floorings that were cleaned. The contribution of the cleaning products to sewage pollution with environmentally hazardous substances was studied at full scale. All commercially available cleaning products studied were declared to be environmentally friendly (labeled with the EU Ecolabel). However, despite being labeled as “green” products, between 16 and 24 volatile harmful ingredients were identified. An optimized experimental product, produced completely from natural raw materials, also contained several harmful substances originating from the herbal raw materials themselves. During the field study, we identified a range of trace substances in the sewage. Eight of these substances (e.g., p-cymene, butanone, eucalyptol) significantly originated from the cleaning products. Several others may have originated from the cleaning products, but other sources were also possible. The flooring materials that were cleaned contained several harmful substances themselves. The release of some substances (e.g., toluene) into the sewage significantly increased during the cleaning process. Full article