Search Results (325)

The exponential increase in photovoltaic panel (PV) waste highlights the urgent need to develop efficient and sustainable recycling processes. It is estimated that by 2030, 8 million tons of PV modules will reach their end-of-life stage, posing a significant environmental challenge and requiring the development of green technologies for resource recovery. This study assessed the performance of imidazolium-based ionic liquids (ILs) as “designer solvents” for the selective leaching of copper and silver from disused PV panels. Specifically, four quaternary imidazolium salts were evaluated: [Bmim]HSO₄, [Emim]HSO₄, [Bmim]Cl, and [Emim]Cl. Leaching tests were conducted on silicon wafers containing 0.28% Ag and 0.19% Cu under varying temperatures (25, 50, and 80 °C), IL concentrations (20% and 60% v/v), and hydrogen peroxide (H₂O₂) dosages (0% and 3% v/v) as an oxidizing agent. The results identified [Bmim]HSO₄ as the most effective leaching agent. The system achieved a maximum copper extraction of 96.70% at 60% v/v concentration and 80 °C. For silver, the highest extraction of 45.13% was obtained using [Bmim]HSO₄ at 20% v/v and 80 °C. The addition of H₂O₂ was crucial, demonstrating a clear synergistic effect with the imidazolium-based ILs by promoting oxidative dissolution. These findings confirm that imidazolium-based ionic liquids represent a promising and environmentally friendly alternative for the recovery of high-value metals in the circular economy of photovoltaic recycling. Full article

The sustainable recovery of high-value metals from wastewater has garnered significant attention in light of the circular economy and environmental preservation. Because of its appealing characteristics, membrane separation technology is essential for the sustainable and effective recovery of valuable metals from wastewater, in contrast to conventional methods, which are chemical- or energy-intensive. In this study, a rational design approach was utilized to synthesize a metal–organic framework (MOF) using a deep eutectic solvent (DES) as a mediating medium to control the reaction of framework formation and particle properties. While DESs have been widely used for the physical modification of materials, their role as a chemically modifying medium during MOF synthesis for structural tailoring remains less explored. This synthesized MOF (DM-Zn-PDC@MOF) was further introduced as filler in polysulfone (PSf)-based mixed matrix membranes (MMMs). The performance of DM-Zn-PDC@MOF within the polymer matrix was examined. Several characterization techniques were used to thoroughly analyze the morphological, chemical, and physical characteristics of the MMMs and DM-Zn-PDC@MOF. The addition of the filler material significantly enhanced the membrane characteristics, including pure water flux, hydrophilicity, porosity, surface roughness, pore size, and heavy metal resource recovery in comparison with the pristine membrane. Stable incorporation of the filler within the membrane matrix was indicated by much less filler leaching (<5%) at all concentrations. With DM-Zn-PDC@MOF loading, the pure water flux increasedmore than nine times from 102.8 L/m²h (M-0) to 971.5 L/m²h (M-4). The functionalized membranes showed better flux retention in high-value heavy metal resource recovery using simulated wastewater: 871.8 L/m²h when filtering a Pb(II) ion solution (compared to M-0 with flux 120.6 L/m²h) and 526.8 L/m²h when filtering a Cr(III) ion solution (compared to M-0 with flux 97.1 L/m²h). These values represented approximately 7-fold and 5-fold improvements, respectively. Overall, Pb⁺² > Cr⁺³, but the rejection of Cr(III) ions was also improved, when compared with M-0. The high flux of the membrane makes it easier to process large volumes and concentrate metals in the retentate, turning diluted contaminated streams into a concentrated feedstock for subsequent recovery procedures. Full article

Per- and polyfluoroalkyl substances (PFASs) constitute a chemically diverse family of persistent contaminants, the regulation of which is tightening rapidly in Europe and the United States. Granular activated carbon, selective ion exchange, and pressure-driven membranes remove many long-chain PFASs, but their performance is less robust for short-chain and ultrashort species, and all generate concentrated secondary waste streams. Hydrophobic deep eutectic solvents (DESs), including natural deep eutectic solvents (NADESs), have emerged as tunable liquid extractants able to concentrate PFASs into small solvent volumes that can be regenerated or coupled to destruction. This perspective differs from existing DES-PFAS reviews by converting qualitative solvent-selection arguments into a decision framework with explicit acceptance gates: broad PFAS affinity, a component-resolved non-migration specification for treated water, viscosity and mass-transfer limits, regenerability targets, and techno-economic/life-cycle benchmarking against incumbent processes. We refine the bifunctional DES design hypothesis by separating validated regimes from unresolved cases, identifying the reliability limits of COSMO-RS, molecular dynamics, and machine-learning screening, and defining tiered reporting requirements for early-stage studies. The central message is that PFAS-extracting DES should no longer be evaluated only by single-compound removal percentages; they must be judged as integrated, closed-loop treatment materials with solvent losses, regeneration stability, destruction compatibility, cost, and environmental impacts that are quantified from the outset. Full article

The growing demand for vanadium and the environmental threat associated with spent catalyst masses have sparked widespread scientific interest in the recovery of V₂O₅ from deactivated vanadium-based catalysts, including those used in sulphuric(VI) acid production. This review places vanadium(V) recovery in the broader context of resource efficiency and the circular economy. The main deactivation mechanisms are analysed, including poisoning, sintering, and structural changes affecting catalytic activity and vanadium availability. Hydrometallurgical approaches to vanadium recovery are discussed, with a particular focus on leaching agents, vanadium speciation in aqueous media, and subsequent separation techniques such as adsorption, solvent extraction, and vanadium(V) precipitation. Key process parameters influencing recovery efficiency, including temperature, pH, and caustic composition, are discussed to provide a comparative assessment of existing methods. The analysis highlights the advantages and limitations of current recovery methods and identifies gaps related to selectivity, process integration, and environmental impact. Overall, the study demonstrates that effective V₂O₅ recovery requires a thorough understanding of catalyst deactivation and solution chemistry. It also outlines models for developing more sustainable and economically viable recycling strategies. Full article

Mining activities generate large volumes of waste that pose both environmental liabilities and potential secondary resource value. A significant fraction of these materials still contains recoverable copper, making leaching a promising strategy for reprocessing and valorization, given the natural decline in ore grade. This study presents a PRISMA-based systematic review of recent literature on leaching technologies applied to mining waste, with emphasis on technical performance, environmental implications, and economic feasibility. The reviewed residues include tailings, slags, copper smelter dusts, sludges, waste rock, leaching residues, and other secondary mining and metallurgical wastes. The main leaching routes identified were acidic, biological, alkaline, and hybrid systems, including conventional H₂SO₄ leaching, pressure oxidative leaching, chloride-based systems, glycine- and ammonia-based alkaline media, organic acids, deep eutectic solvents, and biologically mediated processes. Reported Cu recoveries ranged from low values in refractory systems to near-complete extraction under optimized conditions. Overall, copper recovery was controlled primarily by the mineralogical occurrence of Cu rather than by leaching category alone. In contrast, the highest recoveries were generally associated with intensified conditions capable of overcoming sulfide- and silicate-related constraints. Environmental and circular economy benefits were frequently claimed but less often demonstrated through direct evidence, while economic assessment remained limited. Future research should better integrate mineralogical interpretation, environmental verification, and economic feasibility. Full article

Oil sands tailings from tailings solvent recovery units (TSRU) contain elevated sulfide minerals and can generate acid mine drainage (AMD) upon atmospheric exposure. This study investigated how prior weathering influences acidity and solute release under controlled laboratory conditions. A six-month column leaching experiment was conducted using TSRU tailings with distinct exposure histories: weathered and semi-weathered tailings from a previous greenhouse-scale reclamation capping experiment, along with weakly weathered tailings stored in sealed barrels. Columns were subjected to repeated wet–dry cycles, analyzing the geochemistry of the leachate and solid-phase changes using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). All treatments produced highly acidic leachates (pH < 2), indicating that TSRU tailings retain the capacity to generate acidity regardless of prior exposure. However, the dominant geochemical mechanisms differed by weathering history. Weakly weathered tailings generated progressive increases in acidity and solute release, consistent with active sulfide oxidation. Semi-weathered tailings had more stable responses, suggesting partial sulfide depletion and secondary phase formation. Weathered tailings produced leachates showing evidence of rapid flushing with limited new solute generation. After leaching, residual pyrite remained in all materials, with shifts in surface sulfur speciation providing evidence of progressive surface sulfur oxidation, transformation, and the redistribution of sulfate phases. These results demonstrate the mechanisms involved in AMD generation in TSRU tailings, highlighting the importance of the weathering history and the need for field-scale validation. Full article

Magnetic nanomaterials (MNMs), particularly magnetically recoverable systems with efficient regeneration capability, have emerged as highly efficient nanoadsorbents for water purification owing to their high surface area, tunable surface chemistry, and facile magnetic separation. This review critically analyzes recent advances (2022–2025) in the multi-cycle use of MNMs, with particular emphasis on regeneration strategies. The major syn-thesis approaches and adsorption mechanisms are discussed in relation to their influence on long-term stability. Recent studies demonstrate that many MNMs retain 85–90% of their removal efficiency over 3–6 cycles, although performance degradation due to aggregation, leaching, and surface passivation remains a key challenge. Regeneration techniques, including chemical, solvent-based, and thermal methods, are evaluated in terms of efficiency and feasibility. Moreover, bibliometric analysis reveals the increasing research focus on recyclable nanomaterial design. Overall, this review elucidates the structure–performance–stability relationships governing multi-cycle operation, with a particular focus on reusable and magnetically separable systems and provides insights into the economic feasibility of regenerable MNMs along with future perspectives for sustainable and scalable water treatment applications. Full article

Removing altered varnishes and retouching from oil paintings is a delicate and irreversible procedure in the conservation of cultural heritage. Surfactant-free gelled o/w emulsions containing dibasic esters (DBE) provide a green, safe, and environmentally friendly alternative to traditional solvent methods. The use of Xanthan gum and polyacrylate as thickening agents successfully restricted solvent diffusion, thereby minimizing the risk of interaction with water-sensitive substrates. Spectroscopic and microscopic analyses (FTIR and SEM) were employed to evaluate the cleaning efficacy and to assess the morphological integrity of the paint surface post-treatment, detecting potential inhomogeneities, erosion, or pigment loss. Determination of surface conductivity has allowed us to verify the degree of removal of any residues that could have undesirable long-term effects. Fatty acid leaching was quantified by gas chromatography-mass spectrometry (GC/MS): the use of free DBE resulted in a loss of up to 60% of the lipid component, while for surfactant-free gelled o/w emulsions with DBE, this figure was significantly reduced, with no observable surface damage. The tests were performed at both neutral pH and pH 8.5. The pH change was consistent with expected values: alkaline and ionizing conditions enhanced the emulsifying and removal effect, as well as the interaction with the painting medium. These results suggest that surfactant-free gelled o/w emulsions represent a promising alternative to conventional solvent-based systems, offering effective varnish removal while minimizing risks to both artifacts and restorers. Full article

Limonitic laterites typically contain low Ni and Co contents and significant impurities, making the development of technical and economically feasible processes challenging. To address this challenge, this study investigates and evaluates an integrated hydrometallurgical process comprising sulfation roasting, water leaching, and solvent extraction (SX) for the selective recovery of Ni and Co from limonite-type laterite. Response Surface Methodology coupled with a Central Composite Design (RSM-CCD) was employed as a statistical experimental design tool to efficiently optimize the sulfation roasting conditions. Under the optimal sulfation roasting conditions (temperature 703 °C), selective leaching efficiencies of 87.2% for Ni and 96.6% for Co were achieved, with only 3.8% Fe co-leaching. A multi-stage SX scheme was subsequently applied to purify the pregnant leach solution (PLS) of water leaching. In the first SX step, D2EHPA at pH 2.8 selectively removed more than 95% of the impurities, including Mn, Zn, Al, Ca, and Fe. In the second SX step, Cyanex 272 at pH 5.8 enabled the extraction of more than 99.9% of Co and 86.0% of Mg into the organic phase, and Ni remained in the raffinate. Subsequent stripping with H₂SO₄ enabled the recovery of 99.9% of both Co and Mg from the loaded organic phase. Finally, selective carbonate precipitation is proposed as a potential downstream recovery method for Ni after enrichment. This approach is considered relatively less energy-intensive than sulfate crystallization. The process developed in this study was benchmarked against similar processes reported in the literature, and a conceptual flowsheet for the selective extraction and separation of Ni and Co from limonitic laterite was proposed. Findings demonstrated the feasibility of the integrated sulfation roasting-water leaching, solvent extraction process for treating impurity-rich laterite leach solutions. Full article

Platinum group metals (PGMs), platinum (Pt), palladium (Pd) and rhodium (Rh), are critical for automotive emission control, chemical manufacturing and emerging energy technologies, yet their supply is limited and geographically concentrated. Their designation as critical raw materials (CRMs) in the EU has intensified recycling efforts, especially from spent automotive catalysts. Conventional pyrometallurgical and acid-based hydrometallurgical routes achieve high recovery efficiencies but rely on aggressive reagents and energy-intensive processing. Deep eutectic solvents (DESs) have emerged as greener leaching media capable of dissolving PGMs under milder and tunable conditions. This review outlines the conventional hydrometallurgical framework, summarizes DES fundamentals relevant to metals dissolution, and critically assesses recent advances in DES-based leaching of PGMs from spent catalysts. The influence of solvent composition, oxidants and complexing ligands on PGMs speciation and recovery is discussed, together with emerging reporting guidelines and research priorities. Overall, DES-based leaching offers a promising and potentially safer route for autocatalyst recycling but the technology remains at an early stage of development, requiring further mechanistic insight and sustainability evaluation. Full article

Arsenic pollution is a prevalent challenge worldwide due to extensive use dating back thousands of years, and the pentavalent species arsenate (As(V)) is of particular interest because it predominates in oxygenated groundwater. Metal–organic frameworks (MOFs), characterized by their high surface area and tunable surface chemistry, have emerged as promising adsorbents for its rapid and efficient removal. This study systematically evaluated the adsorption performance, physicochemical properties, and regeneration behavior of monometallic Fe-BTC MOF and bimetallic Fe/Cu-BTC for As(V) removal under application-relevant conditions. Fe-BTC exhibited the highest adsorption capacity of As(V) (117.5 mg g⁻¹), whereas Fe/Cu-BTC showed a lower capacity (74.6 mg g⁻¹). Adsorption in tap water decreased slightly for both materials (19–23%), indicating mild competition from coexisting ions. The adsorption behavior followed the Freundlich model, indicating competitive occupation of high-energy sites on Fe-BTC. In contrast, the surface heterogeneity of Fe/Cu-BTC remained unchanged, highlighting its robust characteristics. Adsorption was strongly pH-dependent, reaching a maximum at neutral pH, and regeneration experiments identified ethanol as the most effective desorption agent for Fe-BTC, enabling reuse. Metal-leaching analysis confirmed superior Fe-BTC MOF stability and minimal leaching, whereas Fe/Cu-BTC instability demonstrated risk of secondary Cu contamination. Overall, these findings establish that Fe-BTC and Fe/Cu-BTC MOF are effective for As(V) adsorption, but Fe-BTC outperforms Fe/Cu-BTC as a practical adsorbent. Significantly, Fe-BTC performance is strongly influenced by water matrix composition and regeneration solvent, highlighting considerations for real-world applications. Full article

The strong adhesion between cathode materials and aluminium (Al) foil substrates presents a significant challenge in the recycling of spent lithium-ion batteries (LiBs). Conventionally, high temperatures and high concentrations of costly organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) are used to enhance ultrasonication-based delamination. In this study, a novel, eco-efficient approach was demonstrated for delaminating cathode materials from Al foil using a low-concentration organic citric-acid-assisted low-power ultrasonic treatment coupled with a gentle, low-power-per-volume mechanical mixing system at room temperature. The separation mechanism was attributed to the structure disruption, possibly swelling, of the polyvinylidene fluoride (PVDF) binder using low-concentration citric acid and the cavitation effects induced by ultrasound. Key parameters influencing the delamination efficiency included the solvent type, temperature, ultrasonic power, and treatment duration. Under optimised conditions, citric acid was used as the sonication reagent, with a process temperature of 20 °C, 60 W ultrasonic power, and 80 min of ultrasonication; a delamination efficiency of approximately 92% was achieved. The recovered cathode materials exhibited low agglomeration, favouring subsequent leaching processes. This work proposes an environmentally friendly and effective method for cathode and Al foil recovery from spent LiBs, integrating manual dismantling, ultrasonic treatment, and material separation. Full article

Ferronickel slag, as a major solid waste in the stainless-steel industry, poses a serious threat to the environment due to its large-scale production and low utilization rate. In this study, magnesium oxide in the ferronickel slag was leached out and converted into high-purity magnesium sulfate, while the leach residue was utilized for cement clinker production. During the complete utilization of ferronickel slag, the Mg leaching efficiency reached 90.75% and was significantly enhanced by reducing the particle size of the ferronickel slag with H₂SO₄ solution as the sole solvent. High-purity magnesium sulfate with a purity of 99.92% was prepared from the leachate through a multi-step process involving primary crystallization, purification, and secondary crystallization. The leach residue, accounting for 68.20% of the original mass, was primarily composed of 79.4 wt% SiO₂ and less than 6.1 wt% MgO and is used as a key raw material in the production of Portland cement. Sintering temperature significantly influenced the structure and properties of the resulting cement. Both the Portland clinker and cement were successfully produced at sintering temperatures of 1400 °C and 1450 °C when the leach residue was used as a primary raw material, with well-developed cementitious phases of calcium silicate and aluminate formed during calcination. The setting time, soundness, and compressive and flexural strengths of the hardened C1400 and C1450 mortars met the requirements specified in relevant standards. Through this integrated process, the overall utilization rate of the ferronickel slag reached 100%. Based on a preliminary estimate, full utilization of the annual ferronickel slag production in China could substitute at least 19.5 million tons of magnesite and 15.0 million tons of silica and reduce CO₂ emissions by 10.3 million tons. Full article

The ability to precisely control the morphology of polylactide (PLA) microparticles is crucial for their biomedical applications, yet it is a challenge due to the interdependent nature of key parameters such as size, porosity, and surface topology. This study presents a systematic approach to fabricating PLA microparticles with tunable architecture via emulsion-solvent evaporation by investigating the interplay of polymer molecular weight (44–442 kDa), solution concentration (0.5–20% w/v), and porogen type (PEG, alkanes, lithium salts). We achieved precise size control from 5 to 500 μm, dictated by solution viscosity and the polymer’s crystallization tendency, with poly(L-lactide) yielding irregular particles and poly(D,L-lactide) forming perfect spheres. Furthermore, porogen selection was critical for porosity: alkanes enabled tailored pore networks, with longer chains (e.g., decane) producing larger pores via enhanced phase separation, whereas the double-emulsion method with Li₂CO₃ proved superior for macroporosity due to its slow leaching kinetics. This work provides a foundational guideline for the rational design of PLA microparticles with customized properties for targeted applications in drug delivery and tissue engineering. Full article

Conventional hydrometallurgical processes typically employ inorganic acids as leaching agents; however, these processes are frequently associated with significant environmental pollution and suffer from poor metal selectivity. Oxalic acid, as a green alternative leaching agent, demonstrates considerable application potential owing to its mild acidity, strong reducing capability, and superior complexing properties. This paper presents a systematic review of recent advances in the application of oxalic acid in hydrometallurgy, encompassing the coordination chemistry between oxalic acid and metal ions, its role as a selective leaching agent, and strategies for handling multicomponent oxalate-rich solutions. Furthermore, the industrial prospects of oxalic acid-based leaching technologies are discussed. Research indicates that oxalic acid exhibits high selectivity and efficient leaching performance for critical metals—including vanadium, lithium, cobalt, nickel, and gallium—from both primary ores and solid secondary resources. The underlying leaching mechanism primarily involves the formation of stable chelation complexes between oxalate anions and high charge-density metal ions, or valence state modulation via reduction, enabling selective dissolution and separation of target metals. In multicomponent oxalate systems, where metals predominantly exist as anionic complexes, established enrichment and purification approaches include anion exchange extraction, as well as precipitation techniques based on valence adjustment and double salt crystallization. To advance the industrial implementation of oxalic acid leaching technologies, further in-depth investigation is required into the recycling mechanisms of oxalic acid and the fundamental reaction pathways governing leaching and metal recovery processes. Full article