Sustainable Chemistry

Wheat straw is an abundant agricultural residue with high potential for carbohydrate-based bioconversion, yet its efficient utilization is limited by lignocellulosic recalcitrance. This study systematically investigated Organosolv extraction of wheat straw (Triticum aestivum) with the goal of achieving near-complete enzymatic hydrolysis at minimized process severity and energy demand. Process severity was evaluated using the P-Factor concept. In preliminary screening, acid catalysts and liquor ratios were assessed. Strong acids clearly outperformed weak acids: at comparable severity, 5% (w/w, DM) H₂SO₄ or p-toluenesulfonic acid (PTSA) yielded glucose yields of 83 ± 2.4% and 81 ± 6.2%, respectively, whereas weak acids (phosphoric, lactic, acetic) and a catalyst-free control resulted in only ~20–41% glucose yield. Liquor ratio strongly affected extraction performance; a ratio of 1:19 provided the highest glucose yield (85 ± 1.4%) and robust mixing compared to 1:12–1:15 (67–68%). Two novel pretreatment strategies applied prior to Organosolv extraction, namely Hot-Water Pretreatment (HWP) and Water Pretreatment (WP), significantly increased hydrolysability compared to untreated straw (58 ± 3%), reaching 79 ± 2% for HWP and 86 ± 5% for WP. DoE-based experiments (135–170 °C; P-Factor 3.0–4.0) showed that increasing temperature from 135 to 150 °C markedly improved hydrolysability (e.g., WP: 74 ± 3% to 96 ± 3%), while further increasing to 170 °C provided no additional benefit. Response-surface modeling predicted a maximum hydrolysability of approximately 88% for HWP but complete hydrolysis for WP within 152–170 °C, indicating a broad operational window. Overall, combining simple Water-based Pretreatment with severity-optimized Organosolv extraction enables energy-efficient, near-complete hydrolysis at lower operating temperatures, reducing both energy demand and pressure requirements, and thereby offering advantages in process cost and scalability. Full article

The adsorption and activation of CO₂ on Cu_xSc_y nanoclusters with x + y equal to 4 were analyzed using DFT and PDOS and TDOS signatures. The geometries of Cu₃Sc, Cu₂Sc₂, and CuSc₃ were optimized in the gas phase, and the minima were verified by frequencies in ORCA using M06-2X/def2-TZVP. Multiplicities 1, 3, and 5, temperatures between 298 and 400 K, and four CO₂ coordination modes R1 to R4 were evaluated. Naked and complex cluster comparison panels were constructed, and two energy windows, −18 to −10 eV and −8 to 6 eV around the Fermi level, were analyzed, complemented by frontier orbitals and charge maps. Thermodynamics indicated that mode and multiplicity control the adsorption energy, with ANOVA p-values of 0.002 and 0.008, while temperature was not significant (p = 0.682). In Cu₃Sc–C₂v(1), the R1 singlet at 298 K showed E_ads −33.43 kcal·mol⁻¹ with spin contamination, while alternative modes in the singlet were unfavorable. In PDOS and TDOS, the bare cluster exhibits a Cu d band at −11 to −10 eV and a valley around −5 eV. The exergonic complexes show CO₂ signals near the Fermi level, superimposed on Cu and Sc states, with state filling and broadening. Transferable indicators based on CO₂ intensity in the −8 to 6 eV range and metal–adsorbate overlap are proposed as predictors of exergonic adsorption. Full article

This study investigated the effects of adding lignin nanoparticles (LNPs) to glycerol-plasticized chitosan nanocomposite films (pCS-LNP). Specifically, different LNP sizes (mean hydrodynamic diameters of about 70, 125 or 170 nm) and loadings (1, 3 or 5% of CS) were studied. The two largest LNP types aggregated mostly in the upper side of the cast films, while the smallest LNP type was found more uniformly throughout the film cross-section. The results showed a trade-off between film properties. Both UV barrier, visible light opacity and antioxidant properties increased with increasing LNP loading, while smaller LNPs resulted in higher stiffness and tensile strength than larger types. The radical scavenging activity of the films correlated with the migration of lignin-derived substances out of the films. Full article

This study presents the synthesis and ball-milling modification of titanite (CaTiSiO₅) powders to enhance the thermal stability and performance of polypropylene (PP) separators for lithium-ion batteries (LIBs). CaTiSiO₅ was synthesized using a ceramic route, and the experimental design varied the milling cycles and sphere sizes. Characterization techniques, including scanning electron microscopy, X-ray diffraction, Fourier-transform infra-red spectroscopy, surface area analysis, thermal analysis, and electrochemical tests, confirmed the production of high-purity monoclinic CaTiSiO₅. Ball milling effectively reduced the particle and crystallite sizes while increasing the specific surface area, total pore volume, double-layer capacitance, and ionic conductivity, while also reducing the cell resistance. Coating PP separators with the modified CaTiSiO₅ significantly improved their thermal stability and enhanced their electrochemical properties, including the electron transfer rate and Coulombic efficiency. These findings demonstrate the potential of ball-milled CaTiSiO₅ as a valuable material for developing safer and more efficient LIBs. Full article

This paper aims to analyze the biodegradation behavior of a common synthetic fiber, well-known for its environmental recalcitrance: polyamide 6.6. In particular, polyamide 6.6 fabrics finished with chitosan to impart antibacterial properties and the natural red dye carmine were studied. Fabrics of standard polyamide 6.6 served as references. Some specimens were buried in compost-enriched soil for 1, 2 and 3 months and kept in the laboratory; simultaneously, others were placed in an outdoor house garden to simulate landfill conditions. After each sample withdrawal, various characterization techniques were employed to assess the status of the fibers. The first evidence was that, in general, there were no weight changes or significant macroscopic damage within three months, except for white stains as an index of microorganism colonization, which was confirmed by microscopic analyses, where bacteria and fungi could be clearly seen. On the one hand, some effects were revealed during the burial in the house garden that impacted the fabrics’ surface characteristics in terms of interaction with soil derivatives (susceptibility to adsorption of water and soil-derived substances). On the other hand, the samples buried under laboratory conditions showed a weak antibacterial efficacy, leading to the hypothesis that more aggressive degradation may have occurred at the expense of chitosan. Still, three months of burial led to mild surface deterioration, opening possibilities for further research. Full article

In this paper, batch stirred-tank alcoholysis reactions of used and refined sunflower oils were performed with n-octyl, myristyl, cetyl, oleyl, and stearyl alcohols using immobilized lipases Novozym 435 and Lipozyme IM as catalysts. Alcohol conversions ranged from 74% to 94%, with slight differences between used frying sunflower oil and refined sunflower oil. The resulting wax esters were purified via stepwise column chromatography. The different regioselectivity of the biocatalysts led to distinct reaction pathways, and Novozym 435 proved to be the most effective enzyme, providing higher conversions and no detectable by-products. This study demonstrates the valorization of waste frying oils into high-value wax esters through enzymatic alcoholysis, comparing two industrially relevant immobilized lipases and achieving high conversion across multiple long-chain alcohols. The results highlight a sustainable alternative to conventional chemical catalysis and extend biocatalytic applications beyond traditional biodiesel production. By incorporating waste lipids into value-added products, the overall sustainability and circularity of the system are improved, contributing to green and sustainable chemistry. Full article

The development of sustainable biorefining processes is essential for increasing the value of lignocellulosic resources and reducing the environmental footprint of the forest-based industry. Birch wood is one of Latvia’s most abundant renewable feedstocks, yet current catalytic technologies for furfural production—primarily based on sulfuric acid (H₂SO₄)—cause extensive cellulose degradation and generate sulfur-containing residues that hinder further valorization. This study proposes an integrated biorefining approach in which orthophosphoric acid (H₃PO₄) is utilized as an alternative catalyst to selectively convert hemicellulose into furfural and acetic acid while preserving cellulose in birch veneer chips (BVC). The experimental plan was based on a full central composite circumscribed (CCC) response surface methodology (RSM) design, which consists of factorial points, axial (star) points, and centre points. In total, 26 experimental runs were performed, including 24 non-centre points (comprising both factorial and axial points (±α)) and two centre points. The optimized conditions enabled high acetic acid yields (6.29–6.48% o.d.m., corresponding to 98–100% of theoretical), furfural yields of 8.75–10.41% o.d.m. (57–68% of theoretical), and exceptional glucan preservation (38.84–40.92% o.d.m., 94–99% of theoretical). Compared with sulfuric acid pretreatment, the H₃PO₄-based process significantly reduced cellulose degradation and improved the suitability of the resulting lignocellulosic residue for subsequent 5-hydroxymethylfurfural (5-HMF) production and other biorefining routes. The findings demonstrate that orthophosphoric acid catalysis is a promising pathway for integrating furfural extraction with cellulose-retentive pretreatment, thereby enhancing the sustainability, efficiency, and circularity of birch veneer chips’ biomass utilization. Full article

A commercially available attapulgite sample (Red Attapulgite) was acid-pretreated to enhance its catalytic activity. It turned out to efficiently facilitate the dehydration of a range of substituted alcohols. The dehydration of the primary alcohol was conducted at 150–180 °C, which represents energy-saving conditions when taking into account the typical dehydration conditions of primary alcohols with temperatures of >300 °C. The alkene yields obtained in this study were found to be comparable to those when utilizing commercially available montmorillonite as catalysts, thereby underscoring the potential of the acid-pretreated attapulgite as a catalyst for a variety of reactions. In a parallel study, dehydration catalyzed by a range of Brønsted acids was investigated. However, only two of these acids were found to be suitable for the dehydration of primary alcohols. Nevertheless, these acids lacked both dehydration activity and recyclability. Therefore, a recyclability study was conducted in the presence of the acid-pretreated attapulgite sample. It is remarkable that no loss of activity was found over five cycles. We hypothesize that after acid-pretreatment, a synergistic effect of the Brønsted and Lewis acid sites is the cause for the high catalytic activity of the sample. Full article

Natural deep eutectic solvents (NADES) are gaining interest as environmentally friendly alternatives to conventional organic solvents in the functional food sector. Their low volatility, biodegradability, and tunable polarity, combined with high affinity for phenolics, carotenoids, and other phytochemicals, make them particularly relevant for developing antioxidant and anti-inflammatory ingredients at a time of rising diet-related chronic disease burden. This review critically analyses the role of NADES along the functional food chain. We summarize their composition, preparation, and key physicochemical properties, and then examine the NADES-based extraction of antioxidant and anti-inflammatory compounds from plants and food by-products in comparison with traditional solvent systems. The influence of NADES on the stability and biological activity of recovered compounds is discussed, together with their use in the formulation, stabilization, and delivery strategies for functional foods. Emerging data indicate that NADES often enhance extraction yields and may protect labile bioactives, leading to stronger antioxidant and anti-inflammatory responses in vitro compared with ethanol or water extracts when normalized to phenolic content. At the same time, large-scale implementation is limited by challenges related to safety assessment, regulatory acceptance, viscosity, and recovery issues, and incomplete techno-economic data. This review highlights these constraints, identifies key knowledge gaps, and outlines research priorities required to translate NADES-based processes into scalable, safe, and health-promoting functional food applications. Full article

Semiconductor manufacturing is a resource and energy-intensive industry with a substantial environmental footprint. To address the footprint, we present a methodology for quantifying the environmental impact of semiconductor unit processes using the Environmental Footprint 3.1 Life Cycle Impact Assessment (LCIA) framework, focusing on identifying improvement opportunities in process steps with less sensitivity to defects. We apply this methodology to backside wet cleaning by proposing an alternative single-wafer process that adopts ozonated chemistries. The assessment used primary data from imec’s 300 mm pilot line. Results show that the proposed process reduces the total environmental footprint by 55% compared to the baseline Spin Cleaning with Repetitive use of Ozonated water and Diluted HF process. Key reductions include 67% less electricity for cleaning, 59% less HF use, and a 31% reduction in ultrapure water consumption. When scaled to a facility producing N28 Logic wafers at 50,000 wafer starts per month, with 46 backside clean steps per processed wafer, the process achieves annual savings of approximately 4 million kWh of electricity and 28 million liters (28,000 m³) of tap water per year. A sensitivity analysis revealed that replacing fossil-based electricity with hydroelectric power further reduces total environmental impacts by up to 63%, emphasizing the benefit of combining process innovation with renewable energy sourcing. Full article

Accurate prediction of the Langelier Saturation Index (LSI), an indicator of water’s scaling and corrosive potential, is vital for water treatment and infrastructure maintenance. In this study, five machine learning models (Ridge Regression, Support Vector Machine, Random Forest, Deep Neural Network, and XGBoost) were applied to predict the LSI from physicochemical characteristics of groundwater in the Morava River basin (Serbia). Rigorous data preprocessing (outlier removal, missing data handling, z-score normalization) and feature selection were performed to ensure robust model training. Models were optimized via 10-fold cross-validation on a 70/30 train–test split. All models achieved high predictive accuracy, with ensemble methods outperforming others. XGBoost yielded the best performance (R² = 0.98; RMSE = 0.06), followed closely by Random Forest (R² = 0.95). The linear Ridge model showed the lowest (yet still strong) performance (R² = 0.90) and larger errors at extreme LSI values. Feature importance analysis consistently identified pH as the most influential predictor of the LSI, followed by alkalinity and calcium. Partial dependence plots confirmed that the models captured established nonlinear LSI behavior. The LSI rises steeply with increasing pH and moderately with mineral content. Overall, this comparative study demonstrates that modern machine learning models can predict the LSI accurately, providing interpretable insights through feature importance and dependence plots. These results underscore the potential of data-driven approaches to complement traditional water stability indices for proactive water quality management. Full article

A sustainable circular pathway was developed for poly(ethylene terephthalate) (PET) nanocomposites through a catalyst-driven polymerization and depolymerization process. In this study, calcium dodecylbenzene sulfonate with n-butyl alcohol modified ZnAl layered double hydroxides (LDHs) were utilized as bifunctional catalysts to synthesize highly exfoliated PET/LDH nanocomposites via in situ polycondensation of bis(2-hydroxyethyl) terephthalate (BHET). The organic modification of LDHs expanded interlayer spacing, improved interfacial compatibility, and promoted uniform dispersion, leading to enhanced mechanical, thermal, and barrier properties. In the second stage, the pristine LDH catalyst efficiently depolymerized the prepared PET/LDH nanocomposites back into BHET through glycolysis, completing a closed-loop BHET-to-BHET cycle. This integrated strategy demonstrates the reversible catalytic functionality of LDHs in both polymerization and depolymerization, reducing metal contamination and energy demand. The proposed approach represents a sustainable route for designing recyclable high-performance PET nanocomposites aligned with the principles of green chemistry and circular material systems. Full article

This work used activated carbon material obtained by chemical activation of abundantly available agricultural sunflower waste residues to remove metol (4-(methylamino) phenol sulfate, MTL) from aqueous solutions. The adsorbent structure was characterized using SEM-EDS and FT-IR spectroscopy. A modified screen-printed carbon electrode (SPCE) with gold nanoparticles synthesized using the Laser Ablation Synthesis in Solution (LASIS) method was used to detect MTL. The successful LASIS formation of gold nanoparticles was confirmed by the specific dark burgundy–red color. TEM measurements showed uniform pseudo-spherical particles with an average diameter of 7.9 ± 0.2 nm. The modified electrode showed improved electrochemical activity, which was confirmed by comparing it with an unmodified electrode using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode was subsequently used to optimize the MTL detection conditions. UV–Vis spectroscopy was used to optimize the adsorption conditions, with the optimal values for pH and contact time found to be 8 and 120 min, respectively. The electrochemical detection of MTL was performed using differential pulse voltammetry, and the linear calibration range was established for concentrations ranging from 0.73–49.35 µM. The obtained limits of detection (LOD) and quantification (LOQ) were 0.06 µM and 0.2 µM, respectively. The efficiency of MTL removal was 100% after a contact time of 1 min and remained at 100% after 120 min. Full article

Biogenic nanoparticles have recently emerged as promising bacterial growth inhibitors, requiring low concentrations and not producing harmful byproducts. However, knowledge gaps remain regarding how different extraction techniques affect nanoparticle synthesis, thereby influencing their replicability and scalability across various applications. To address these knowledge gaps, this study compared six extracts derived from Moringa oleifera biomass for the synthesis of iron oxide nanoparticles. Multivariate statistical analyses correlated extraction methods with biomolecule content (polyphenols, flavonoids, carbohydrates, proteins), iron percentage, and E. coli growth inhibition. All extracts showed varying concentrations of biomolecules, and different extraction methods were preferable for specific components. Flavonoids were best extracted by salting-out, while infusion methods were better for obtaining carbohydrates. Higher percentages of iron (22.77%) were linked to the presence of polyphenols and flavonoids. Nanoparticles prepared using salting-out and infusion extraction from leaf biomass displayed the highest efficiency in inhibiting E. coli growth, up to a dilution factor of 4. The outcomes of this research study provide an in-depth understanding of the role of specific biomolecules in biogenic nanoparticle synthesis, confirming that both synthesis yield and application effectiveness depend on the extract preparation method. Full article

Water-based drilling fluids (WBDFs) are widely used due to their economic and environmental advantages; however, shale hydration remains a major limitation. This study evaluates Fe₂O₃, CuO, ZnO, and MgO nanocrystalline metal oxides synthesized via co-precipitation as inorganic shale inhibitors for WBDFs. Comprehensive characterization confirmed phase-pure nanocrystalline oxides (17–38 nm) with high thermal stability. Performance tests revealed that MgO-based WBDF exhibited the lowest plastic viscosity (17 cP), the highest pH (≈10.0), and the strongest shale inhibition (6.1% swelling), while Fe₂O₃ provided superior filtration control (6.0 mL). CuO showed balanced rheology, whereas ZnO displayed comparatively weaker inhibition. Compared with commercial inhibitors (Amine NF and Glycol), MgO- and Fe₂O₃-based systems achieved comparable or improved performance with enhanced thermal and environmental robustness. These results demonstrate the potential of nanocrystalline metal oxides as sustainable additives for improving WBDF performance under high-pressure, high-temperature (HPHT) conditions. Full article

This study investigates amorphous anodized porous TiO₂ (a-TiO₂) as a substrate for iridium-based oxygen evolution catalysts. The substrates were prepared via anodization of Ti foil in a glycerol-based solution for 15 min @ 60 V. Nickel was subsequently electrodeposited to act both as a conductive and sacrificial layer for the galvanic deposition of iridium from an Ir(IV) chloro-complex solution. Electrochemical anodization resulted in a uniform IrO_x layer on the a-TiO₂ substrate, featuring Ir aggregates ~250 nm in size and an Ir:Ni atomic ratio of ca. 7, as determined by EDS analysis. The quantity of Ni determined by ICP-MS bulk analysis indicated that Ni resided also within the porous matrix. Varying the Ni deposition charge density (q_Ni) revealed that an intermediate loading (1463 mC cm⁻²) provided the best balance between Ir accessibility during the galvanic replacement step and electronic continuity. The optimized IrO_x/Ir-Ni/a-TiO₂ electrode achieved excellent OER performance (η = 344 mV @ 10 mA cm⁻²; 1.68 mA μg_Ir⁻¹ @ η = 300 mV) at an ultra-low Ir loading of 2.15 μg_Ir cm⁻² and demonstrated good short-term stability, with only a 20 mV potential increase over 4 h of continuous operation at 5.5 mA cm⁻². Overall, this strategy offers a scalable pathway for producing efficient OER electrodes with minimal noble metal loading. Full article

In whey valorization, membrane separation stands out as a highly effective technique for purifying and isolating the various components of whey. The efficiency of whey ultrafiltration and diafiltration (UF/DF) largely depends on the balance between membrane selectivity, hydrodynamic conditions, and solute interactions at the membrane interface. In this study, sweet whey was fractioned using 10, 30 and 50 kDa polyether sulfone (PES) membranes under identical transmembrane pressure (TMP = 2.5 bar) with ultrafiltration and a subsequent 4-step constant volume diafiltration stages. The resulting compositional and dielectric changes were evaluated to identify optimal separation conditions and assess the applicability of dielectric parameter measurement as a rapid, non-destructive monitoring technique. Results showed that, regardless of the applied molecular weight cut-off (MWCO), using three DF cycles can wash out almost all the removable lactose from the retentates, and the dielectric assessment of both permeate and retentate fractions showed a strong, linear relationship between the change in dielectric behavior and the composition of each fraction. Analysis of the dielectric spectra confirmed that the ratio of the dielectric constant to the loss factor (ε′/ε″) exhibited a strong linear correlation (R² > 0.98, r > 0.99) with lactose concentration in the permeate fractions of all three MWCO membranes, as well as a similarly strong correlation (R² > 0.975, r > 0.98) with the total chemical oxygen demand (TCOD) measured in the retentate fractions. Full article

The old spectral displacement method can be suitably revitalized for a didactic experimental approach to fundamental concepts of supramolecular chemistry and to the study of complex equilibria in general. In particular, the case of the β-cyclodextrin/phenolphthalein/adamantane ternary system has been taken into account as a viable and impressive example due to the remarkable color changes that can be observed when performing the experiments. A new method for data regression analysis is proposed, with a smart trick able to overcome the mathematical difficulties arising whenever multiple equilibria must be considered. Hence, some aspects of the reliability of fitting procedures are discussed. Full article

Mercury (Hg²⁺) contamination in water systems poses a severe environmental and health hazard due to its high toxicity and bioaccumulation potential. In this study, a novel adsorbent was developed by sequentially modifying kaolin via acid–base treatment, titanium dioxide (TiO₂) incorporation, and 3-aminopropyltriethoxysilane (APTES) grafting. Batch adsorption experiments revealed that the fully modified kaolin (TiO₂-loaded and APTES grafted) exhibited the highest adsorption capacity (25.6 mg/g) compared to the acid–base-treated (5.8 mg/g) and TiO₂-loaded (17.7 mg/g) kaolin. Under optimal conditions (75 mg adsorbent dosage; 70 mg/L Hg²⁺; pH 5), the fully modified kaolin maintained its performance even in the presence of varying ionic strengths, natural organic matter, and competing metal ions. Adsorption kinetics followed a pseudo-second-order model, and the equilibrium data were well fitted by the Langmuir isotherm. Antibacterial activity assay revealed that the TiO₂-loaded kaolin effectively inhibited S. aureus (minimum inhibitory concentration = 2.5 mg/mL) and showed moderate activity against E. coli (BL21) (minimum inhibitory concentration = 5 mg/mL). However, antibacterial activity decreased after amine functionalization, indicating a compromise between enhancing adsorption capacity and preserving antibacterial functionality. This study presents a promising cost-efficient approach for the simultaneous removal of Hg²⁺ ions from water matrices and inhibiting bacterial growth, aligning with SDG 6 (Clean Water and Sanitation). Full article