Search Results (2,881)

The recycling of post-industrial multilayer polyethylene terephthalate (mPET) packaging waste remains a major challenge due to the coexistence of incompatible polymeric phases and the deterioration of properties during reprocessing. In this work, different reactive compatibilization strategies were evaluated to improve the processability and performance of recycled multilayer PET scraps generated during industrial packaging manufacturing processes. Several functional compatibilizers were investigated, including poly(ethylene-co-acrylic acid) (EAA), poly(ethylene-alt-maleic anhydride) (EMA), poly(ethylene-co-glycidyl methacrylate) (EGMA), poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMAGMA), and maleic anhydride (MA). The influence of compatibilization on the thermal, mechanical, chemical, surface, and morphological properties of recycled mPET was systematically analyzed. Processing behavior revealed that EMA- and MA-based formulations could not be successfully injection molded. In contrast, EAA-, EGMA-, and EMAGMA-based formulations showed suitable processability and enabled the production of defect-free specimens. Thermogravimetric analysis revealed only minor changes in thermal degradation behavior after compatibilization. In contrast, differential scanning calorimetry revealed changes in the melting behavior of the recycled formulations, while tensile and impact tests demonstrated marked improvements in ductility and toughness for EGMA- and EMAGMA-modified systems. Among them, EMAGMA provided the highest elongation at break and impact resistance. Contact angle measurements showed moderate changes in surface wettability, whereas density and hardness remained largely unaffected. FESEM analysis revealed a more homogeneous phase distribution and reduced dispersed-domain size in the compatibilized formulations, particularly for EGMA, indicating improved interfacial compatibility. These results demonstrate that glycidyl methacrylate-based compatibilizers are effective reactive agents for upgrading post-industrial multilayer PET waste into higher-performance recycled materials for different applications. Full article

Metal additive manufacturing (AM) plays an increasingly important role in sustainable production owing to its material efficiency, design freedom, and compatibility with circular economy (CE) strategies. Yet the high cost and environmental burden of producing virgin metallic powders remain major barriers to large-scale adoption. This review synthesizes current and emerging approaches for recycling metallic powder feedstocks within AM, organizing them into four pathways: reusing, reconditioning, repurposing, and resourcing. Reusing preserves powders within the AM loop through controlled handling and qualification strategies, whereas reconditioning applies mechanical, thermal or chemical treatments to restore powder properties. Repurposing redirects powder to alternative value-added routes, including wire feedstock, metal–polymer composites, extrusion materials, and elemental or oxide recovery. Resourcing generates new powder from end-of-life powder, printing scrap, and waste through mechanical size reduction, atomization-based processes, or solid-state conversion routes. Across these pathways, the review highlights technological advances, process limitations, and cross-cutting challenges related to oxidation, morphology deterioration, contamination, and scalability, and identifies underexplored methodologies with potential for AM-specific recycling. By integrating insights across the field, this work outlines the expanding landscape of metallic powder circularity and demonstrates how diversified recycling strategies can reduce environmental impact, lower material costs, and support a more sustainable AM ecosystem. Full article

Plastic waste presents a persistent environmental burden, yet its constituent polymers represent structurally valuable chemical feedstocks. Mechanical recycling remains limited due to polymer degradation, additive contamination, and material downcycling, underscoring the need for alternative strategies. Chemical upcycling offers pathways to convert post-consumer plastics into higher-value monomers, functional chemicals, and bioactive or pharmaceutical precursors by exploiting inherent structural motifs such as aromatic rings, ester linkages, and heteroatom-containing backbones. Approaches such as catalytic depolymerization, molecular functionalization, microbial and enzymatic transformation, and scaffold repurposing enable the recovery of polymer-derived building blocks with improved functional value. Case studies illustrating the conversion of discarded plastics into advanced materials and biologically relevant small molecules demonstrate the potential of these approaches to stimulate innovation and expand sustainable chemical practices. Collectively, such developments align with green chemistry principles, support emerging circular chemical economies, and contribute to global sustainability priorities reflected in the United Nations Sustainable Development Goals. This review aims to outline the guiding principles of chemical upcycling and highlight the challenges in chemical design, encouraging the modern chemistry community to tap into the hidden potential of waste plastics. Full article

Utilization of tetra-n-butylammonium fluoride (TBAF) as a new, hitherto unknown devulcanization aid in the chemical devulcanization of sulfur crosslinked diene rubber has been demonstrated. The influences of crosslink structure (the ratio of mono-, di-, and polysulfidic bonds) and carbon black (CB) loading on the efficiency of acrylonitrile-butadiene-rubber (NBR) devulcanization have been studied. The rubber vulcanizates were treated with TBAF solutions under varying conditions (solution concentration, solvent type, temperature, and reaction time). Changes in crosslink density and other relevant network properties of the rubber vulcanizates were measured. Results showed a significant reduction in crosslink density—up to 50% after chemical treatment. The fluoride-based approach, in which fluoride salt is a source of nucleophilic fluoride anions (F⁻), can cleave the sulfidic crosslinks, demonstrating significant potential for efficient recycling of used rubber vulcanizates by their devulcanization. Full article

Polyethylene terephthalate (PET) is a common plastic widely used in food packaging, especially plastic bottles, and in fibers and textiles. The widespread use of PET and its intentional and unintentional release and disposal over the past few decades have placed significant pressure on the environment, necessitating the development of green, low-cost, and efficient recycling technologies to mitigate this impact. This article reviews recent advances in microwave-assisted catalytic depolymerization of PET. It begins by outlining the fundamental principles of PET materials science and depolymerization mechanisms. The article then reviews the historical evolution of this research and presents a benchmark comparison of different depolymerization methodologies. Finally, through a critical analysis and comparison of state-of-the-art approaches, the article identifies emerging trends and highlights promising directions for future research in the field. A comprehensive comparison of conventional and microwave heating methods is presented, indicating that catalyst-assisted microwave systems can shorten reaction times and achieve high product yields under optimized conditions. Key advantages and limitations are highlighted, and persistent challenges are discussed. Overall, this article surveys the latest progress in the chemical recycling of PET and provides critical insights for future research and further development of microwave-assisted catalytic PET depolymerization technology. Full article

Ion-imprinted polymers (IIPs) are advanced adsorbents featuring selective recognition cavities for targeted metal ion capture, offering a promising route to high-efficiency separation in extractive metallurgy. In the present work, the evolution, design principles, synthesis strategies, separation mechanisms, and practical applicability of IIPs for metal recovery from complex aqueous matrices are overviewed. Key material components, including functional monomers, crosslinkers, template ions, initiators, solvents, and support materials, are discussed in relation to adsorption capacity, selectivity, kinetics, stability, and recyclability. Major preparation routes, such as surface imprinting, bulk polymerization, in situ polymerization, and sol–gel methods, are critically compared to clarify their advantages and limitations. Recent applications for base metals, precious metals, and rare-earth elements demonstrate that IIPs can achieve high specificity and rapid equilibrium under optimized conditions. However, their translation from simulated solutions to real leachates remains constrained by interfering ions, organic contaminants, mass transfer resistance, incomplete template removal, and matrix complexity. Mitigation strategies, including sample pretreatment, improved polymer architecture, and hybrid supports, are therefore emphasized. Additionally, chemometric modelling, machine learning, or artificial intelligence-assisted design may be implemented to advance the prospects of IIPs in industry. Conclusively, IIPs represent a strong separation platform, yet industrial deployment requires robust validation with real feed streams and scalable regeneration protocols during column operation, as well as under chemically aggressive conditions at scale. Full article

This study integrates conventional sediment geochemistry with explainable machine learning to investigate the provenance of surface sediments from Wular Lake, Kashmir Valley, NW Himalaya. Twenty-two samples were analysed for 49 geochemical variables (10 major oxides, 25 trace elements and 14 rare earth elements), complemented by XRD mineralogy, which reveals an assemblage dominated by quartz, muscovite/illite, chlorite and feldspar. The Chemical Index of Alteration (CIA = 68.5–75.1, mean 72.1), corroborated by CIW, PIA and the A–CN–K trend, indicates moderate weathering under a cold temperate climate, and the Index of Compositional Variability (ICV > 1), together with uniformly low Zr/Sc ratios (3.4–6.0), which preclude significant zircon addition through recycling, records compositionally immature, first-cycle detrital input. Conventional discrimination ratios and the Herron system classify the sediments as geochemically equivalent to shale, and elevated Fe₂O₃/K₂O (2.6–4.0), Al₂O₃/TiO₂ (12.6–16.0), Cr/Th and Co/Th ratios record a substantial mafic imprint. Chondrite-normalised REE patterns show pronounced LREE enrichment ((La/Yb)_N = 8.0–19.4), moderate negative Eu anomalies (Eu/Eu* = 0.56–0.73) and negligible Ce anomalies (Ce/Ce* = 0.98–1.03), with Eu/Eu* discriminating felsic crystalline from mafic volcanic contributions. A three-stage pipeline (principal component analysis (PCA) → random forest → SHapley Additive exPlanations (SHAP)) achieved a median leave-one-out cross-validation (LOO-CV) accuracy of 95.5% (n = 22; Wilson 95% CI 78%–99%), and unsupervised k-means clustering reproduced the same three geochemically distinct provenance end-members: siliceous-mature, detrital-mafic and carbonate-bearing, without reference to the assigned labels (Adjusted Rand Index = 1.0). Because the training labels derive from the same geochemical dataset, the classification quantifies the internal consistency of the provenance model, but does not provide independent validation. SHAP analysis reveals that trace elements (Cr, Co, Sc, Ni, Zn) carry greater discriminating power than do conventional major-oxide ratios, demonstrating that explainable machine learning robustly supplements and extends traditional provenance approaches. Full article

Growing demand for more sustainable packaging has increased interest in bio-based adhesives as alternatives to conventional fossil-derived systems. Among renewable raw materials, lignin is particularly attractive because of its aromatic structure, phenolic functionality, and availability as a side stream of pulp, paper, and biorefinery processes. This review critically examines the potential of lignin-based adhesives for packaging applications. Selected polysaccharide-, protein-, vegetable-oil-, and tannin-based systems are briefly discussed as comparative references, while the main focus is placed on the properties of kraft lignin, lignosulfonates, organosolv lignin, and soda lignin. Their structural differences, adhesive behaviour, and suitability for chemical modification through hydroxymethylation, phenolation, demethylation, depolymerization, oxidation, and epoxidation are evaluated. Because most lignin-adhesive research concerns wood bonding, the transferability of these findings to paper, paperboard, labels, coatings, films, and hot-melt packaging adhesives is critically assessed. Direct evidence for packaging applications remains limited, although existing studies demonstrate promising opportunities for paper bonding, pressure-sensitive systems, and paperboard hot-melt adhesives. Key challenges include lignin heterogeneity, processing complexity, moisture resistance, colour, food-contact safety, scalability, and compatibility with recycling. Full article

Municipal wastewater is a major pathway for the continuous release of microplastics into aquatic environments, making the development of efficient and reusable capture materials essential for advanced water treatment. In this study, a multifunctional ZIF-67/g-C₃N₄/CS nanocomposite was designed by integrating cobalt-based zeolitic imidazolate framework ZIF-67 with graphitic carbon nitride (g-C₃N₄) and a chitosan (CS) biopolymer matrix. The novelty of this material lies in combining the high porosity and tunable surface chemistry of ZIF-67, the π-rich layered structure of g-C₃N₄, and the hydrophilic, amino-rich chitosan framework into a single adsorptive platform for simultaneous removal of chemically different microplastics. The nanocomposite achieved high removal efficiencies for polystyrene (PS), polypropylene (PP), and polyethylene (PE) microplastics with particle sizes of 20–25 μm, reaching 97.4%, 92.1%, and 90.3%, respectively, at pH 7.6 within 25 min. The higher affinity toward PS is attributed to additional π–π interactions between the aromatic PS chains and the conjugated domains of g-C₃N₄/ZIF-67, whereas PP and PE removal is mainly governed by hydrophobic adhesion, surface trapping, and interfacial interactions with the chitosan-supported porous framework. The equilibrium data were well described by both Langmuir and Freundlich models, with maximum adsorption capacities of 97.69, 94.86, and 93.67 mg g⁻¹ for PS, PP, and PE, respectively. The nanocomposite retained high recyclability, maintaining 95–97 ± 3.1% removal after five adsorption–desorption cycles. These findings demonstrate that ZIF-67/g-C₃N₄/CS is a durable and high-performance adsorbent for microplastic remediation, with strong potential for application in municipal wastewater treatment, constructed wetlands, and advanced water-polishing systems. Full article

Managing polymer waste, primarily polyolefins—low- and high-density polyethylene and polypropylene—is a critical challenge in the transition to a low-carbon, circular economy. Traditional approaches (landfilling and incineration) are inconsistent with sustainable development principles and increasingly stringent extended producer responsibility regulations, while chemical recycling, particularly catalytic pyrolysis, is considered a key technology for returning hydrocarbon feedstocks to the production cycle. This mini-review systematizes and analyzes current advances in the catalytic pyrolysis of polyethylene and polypropylene. An algorithm for selecting a recycling route for polyolefin-containing waste based on its composition, degree of degradation, and the presence of hazardous additives is proposed. Existing and planned industrial projects in the field of chemical recycling of polyolefins are assessed, and challenges and prospects for technology commercialization are outlined. It is demonstrated that catalytic pyrolysis has the potential to become a key element of a circular economy for plastics, ensuring decarbonization and resource conservation with further optimization of catalysts and process flowsheets. Full article

The world’s food industry faces significant obstacles today as it strives to meet the nutritional needs of its rapidly expanding global population while also managing an immense amount of food processing waste (FPW) generated throughout the entire food supply chain. The widespread use of traditional disposal techniques for food waste (landfilling and incineration) regularly faces challenges related to environmental sustainability and economic efficiency. This manuscript reviews the necessary transition from a linear “take-make-dispose” approach to food production to a more circular model that recycles food waste into high-value intermediate chemicals and renewable energy through the development of biorefineries. The manuscript explores the biochemical composition of food waste, with carbohydrates, lipids, proteins, and bioactive materials, making it a suitable feedstock for different multi-stage biorefinery operations. In addition, this review will evaluate a variety of existing conversion technologies for food processing waste, such as biological methods (e.g., anaerobic digestion and fermentation) and thermochemical methods (e.g., pyrolysis, gasification, and hydrothermal liquefaction), to create various platform chemicals, including organic acids, bio-alcohols and volatile fatty acids (VFAs), as well as the production of sustainable biofuels and biopolymers. The review also elucidates the three most determinative constraints on large-scale industrial implementation of food waste valorisation: feedstock variability, techno-economic feasibility, and the need for comprehensive life cycle assessments (LCAs). The alignment of food waste management strategies with the UN SDGs (in particular, SDG 12 ‘Responsible Consumption and Production’ and SDG 13 ‘Climate Action’) reflects the opportunity for food waste to serve as a foundation for a carbon-neutral, sustainable future. This review provides a strategic roadmap for academics, practitioners, and policymakers to tap into the full potential of food waste through a sustainable circular economy model. Full article

Polyester–cotton (PES/CO) blends represent one of the most widely used textile classifications globally, yet their fibre-to-fibre recycling remains technically challenging due to the chemical dissimilarity of the two fibres. Existing reviews typically address textile recycling in broad terms, leaving a gap in critically evaluating the specific separation chemistries, recovered-fraction quality, and industrial maturity of PES/CO recycling routes. This review addresses that gap by providing a focused and comparative assessment of technologies designed for PES/CO fractionation. The paper analyses both polyester-removal and cellulose-removal routes, covering depolymerisation (hydrolysis, glycolysis, methanolysis, aminolysis), dissolving systems (NMMO, ionic liquids, DES, cold alkaline), and enzymatic or acid-based degradation. Each route is evaluated using technical criteria including fraction purity, cellulose degree of polymerisation, polyester monomer recovery, fibre quality, chemical consumption and energy requirement, solvent recovery, reaction conditions, and scalability. The review finds that chemical depolymerisation of PES and selective dissolution of cellulose currently show the strongest potential for high-quality fibre-to-fibre recycling, particularly when solvent recovery systems are integrated. However, significant barriers remain, including incomplete fraction purity, degradation of cellulose DP, limited recovery of high-quality polyester intermediates, high chemical consumption, and insufficient industrial-scale demonstrations. Overall, this review provides a differentiated and critical synthesis of PES/CO recycling technologies, clarifying their readiness levels and outlining the key scientific and industrial challenges that must be addressed to enable circularity in blended textile waste streams. Full article

Ascorbate (AsA), or vitamin C, is a central redox metabolite that functions as an antioxidant, enzyme cofactor, and electron donor. Its cellular function depends not only on biosynthesis or dietary uptake, but also on rapid recycling from its oxidized forms, monodehydroascorbate (MDHA) and dehydroascorbate (DHA). This requirement is especially evident in high-demand systems such as plant chloroplasts, which face continuous photosynthetic reactive oxygen species (ROS) production under illumination, and human neutrophils, which accumulate millimolar ascorbate to withstand NADPH oxidase-driven oxidative bursts in pathogen defense. Here, we revisit ascorbate recycling from a sulfur-centered perspective. Historical studies of plant, animal, and solution-chemistry pathways show that many DHA-reducing systems converge on sulfur chemistry, including glutathione (GSH), cysteine-dependent enzymes, H₂S, and modified thiols. We propose that ascorbate recycling is organized as a multilayered system in which nonenzymatic reactions are accelerated by enzymes, localized within cellular or extracellular compartments, and integrated with broader NAD(P)H-, glutathione-, sulfur-, and diet-dependent redox networks. Within this framework, the AsA/DHA couple can be viewed as a molecular redox capacitor that buffers transient oxidative pressure. Reactive sulfur species (RSS), including persulfides and polysulfides, represent chemically plausible but experimentally unresolved contributors to DHA reduction. Full article

This paper explores the technical, economic, and environmental viability of producing secondary wrought aluminium alloys from post-consumer scrap. The technical review relates to the industrial-level use of laser-induced breakdown spectroscopy (LIBS) in automated scrap sorting under realistic operating conditions. First, process scrap was used to determine the accuracy of LIBS in sorting and separating wrought aluminium alloys, and then the method was applied to post-consumer scrap streams. The melted products were then analyzed, and their chemical compositions were confirmed using optical emission spectroscopy (OES) to meet the established alloy specifications. The economic analysis compares traditional recycling routes of cast alloys with a second route in which recyclers provide already sorted secondary wrought alloys, with a focus on cost and market feasibility. Simultaneously, an environmental analysis using life cycle analysis (LCA) measures the effects of sorting and manufacturing procedures. The results show that LIBS can effectively sort secondary wrought aluminium under controlled input conditions. The process reaches a break-even point in about five years when a 50% price premium for secondary wrought alloys over mixed scrap is assumed. The method is environmentally beneficial, with the global warming potential per kilogram of aluminium reduced by over 95% compared to the global average. The findings highlight the significant potential of combining advanced sorting technologies, new business models, and sustainability-oriented practices to support the implementation of circular material flows in aluminium recycling. Full article

Background/Objectives: Phenotypic drug tolerance, distinct from genetic resistance, allows Mycobacterium tuberculosis (Mtb) to survive prolonged antibiotic exposure and contributes to treatment failure and relapse. The trehalose recycling pathway, mediated by the LpqY-SugABC transporter, has been implicated as a metabolic “escape” mechanism that sustains Mtb viability under antibiotic and nutrient-limiting stress, making it an attractive target for adjunctive, tolerance-breaking therapeutics. Methods and Results: Here, we conducted a high-throughput phenotypic screen of 50,000 compounds from chemically diverse libraries, using a carbon source-restricted assay that forces Mtb to rely on trehalose uptake for growth, to identify small-molecule inhibitors of this pathway. This approach yielded 23 confirmed hits in Mtb, spanning several chemical scaffolds, including thioureas, propanamides, benzamides, and carboxamides. Using an isogenic set of Mtb wild-type, LpqY-SugABC transposon knockout, and complemented strains, we confirmed that the genetic loss of transporter loss reproduces accelerated killing by isoniazid, rifampicin, and bedaquiline, but not moxifloxacin, and that loss of trehalose recycling sensitizes mycobacteria to oxidative stress. Using orthogonal functional assays, fluorescent trehalose probe (FITC-tre) uptake inhibition and H₂O₂ hypersensitization, thiourea-containing compounds emerged as the candidates most consistent with transporter-specific activity, phenocopying the effects of genetic LpqY-SugABC loss, while biochemical assays against recombinant trehalase (Rv2402) excluded downstream enzymatic inhibition as their mechanism of action. In addition, several hits potentiated rifampicin-mediated killing of intracellular Mtb in THP-1 macrophages, in some cases reducing bacterial burden below levels achieved by monotherapy. Conclusions: These findings indicate that the trehalose recycling pathway is functionally druggable by small molecules identified through unbiased phenotypic screening and nominate thiourea- and propanamide-based scaffolds as priority candidates for further mechanistic characterization, including direct target-engagement studies, and optimization as adjunctive anti-tuberculosis agents targeting drug-tolerant Mtb populations. Full article