Search Results (1,420)

Mine leachate and saline industrial wastewater streams are often treated as liabilities to be remediated or disposed of. These flows often contain substantial water and dissolved mineral resources that can be reclaimed. In this work, a waste-heat-assisted falling-film evaporation reactor was developed and assessed for application as a pre-concentration step before water and mineral recovery processes. Two case studies were considered: synthetic saline wastewater containing 80 g/L Na₂SO₄ and 70 g/L NaCl for salt recovery, and iron-rich mine water containing approximately 4000 mg/L Fe²⁺, 95 mg/L Fe³⁺, and 13,000 mg/L acidity as CaCO₃ for downstream pigment and magnetite recovery. Saline water or mine leachate flows down a bank of vertical conduit pipes as a thin film while air flows through the pipe cores. Heat is transferred to the system from industrial waste gas externally. Psychrometric relationships, heat transfer, energy balances, and techno-economic analysis were used to assess the impact of air temperature, conduit diameter, column height, pipe material, and waste-gas temperature on overall reactor performance. Experiments were carried out to confirm expected psychrometric operation and establish appropriate operating temperatures while confirming the impact of conduit geometry on heat-transfer characteristics. A benchmark case of design evaporation rate equal to 100 L/h was chosen for comparison of all tests. Dry air operation was shown to be technically possible but severely limited by the moisture capacity of air; at 26 °C and 101.3 kPa, approximately 205,000 m³/h of air was required. When using industrial waste heat, the operation changed from psychrometric/mass-transfer-limited to heat-transfer-controlled. Using waste gas entering at 144 °C and exiting at 80 °C reduced airflow requirements to approximately 880 m³/h, allowing a much more compact reactor design with approximately 635 (12 mm diameter) conduit pipes. Relative to the 40 °C air benchmark, electrical power was reduced from approximately 24.7 kW to 2.9 kW, and screening-level reactor cost by ~84%. Findings demonstrated that appropriate waste heat enables the application of evaporation if there is sufficient local heat flux. Smaller conduit diameters, sufficient column height, and greater waste-gas inlet temperatures were all beneficial. Choice of material required trade-offs between heat-transfer coefficient, corrosion, and material cost. Full article

Landfill leachate circuits that operate without discharge, by recirculating aerated leachate onto the waste mass, are widespread in South-East Europe, yet their long-term behaviour is rarely documented with sample-level data. This study reports a six-year (2020–2025) seasonal monitoring campaign at a sanitary landfill in northern Serbia (alluvial aquifer of the Sava River, transboundary Danube basin) and re-examines it with a transparent multivariate protocol. Seventy-two leachate samples (collection well, aeration lagoon, sedimentation lagoon; n = 24 each, 30 parameters), 28 realised surface-water campaigns, and six years of groundwater summaries were evaluated by principal component analysis/factor analysis (PCA/FA, Varimax normalized), hierarchical cluster analysis, PERMANOVA, non-parametric paired tests and, for benchmarking, supervised machine learning. The pooled leachate model (n = 72; 21 variables; KMO = 0.700; Bartlett χ² = 956, p < 0.001) retained four factors by parallel analysis, explaining 61.6% of total variance; after rotation the factors accounted for 27.7%, 14.3%, 10.4%, and 9.3%. Factor 1 grouped organic load with particle-reactive metals (COD, BOD₅, Fe, Ni, Cr, As, Zn), Factor 2 a reduced sulfur–fluoride–BTEX signature, Factor 3 temperature-driven nitritation, and Factor 4 a nitrate–manganese redox contrast. Crucially, paired campaign-by-campaign comparison showed no removal of the dominant pollutants along the circuit. Median COD, BOD₅ and NH₄-N were not lower in the sedimentation lagoon than in the collection well, while pH rose from 8.08 to 8.75 (p < 0.001); only Cu, Pb, NO₃-N, and NO₂-N decreased significantly. The circuit therefore homogenises and concentrates dissolved load rather than removing it. Downstream surface water was significantly enriched in electrical conductivity (+110 µS/cm), total dissolved solids, NH₄-N, and NO₂-N relative to upstream (Wilcoxon, p < 0.05), and groundwater showed episodic conductivity up to 12,760 µS/cm and NH₄-N up to 102 mg/L. Cytotoxicity (MTT) confirmed biological relevance, with MRC-5 viability falling to 37% after 24 h exposure to 50 vol.% groundwater (Pw3) versus 60% in A549 cells. A random-forest classifier separated circuit units far better than PCA-based discrimination (76.4% versus 54.2% cross-validated accuracy) and distinguished the 2020–2021 pandemic period from 2022–2025 with 94.2% accuracy, a period effect also confirmed by PERMANOVA (R² = 7.2%, p < 0.001). The results indicate that closed-loop recirculation without an engineered discharge barrier transfers, rather than eliminates, contaminant load, and that after-care of such systems requires mass-balance monitoring and polishing treatment. Full article

Effective iron removal from highly acidic leachates without neutralizer addition is a long-standing challenge in hydrometallurgy. For Cu-Co-bearing pyrite cinder, we demonstrate that a cyclic leaching process achieves this outcome. Operating entirely without neutralizers, the process consumed 96% of residual acid, enriched Cu and Co 4.76- and 3.88-fold, and removed 48.2% of iron, all while maintaining pH below 1.5 across four closed-loop cycles. Thermodynamic analysis reveals that Fe³⁺-${\mathrm{SO}}_4^{2-}$ complexation suppresses free Fe³⁺ to approximately 10⁻⁸ mol/L, ruling out conventional hydrolytic precipitation and directing precipitation towards schwertmannite-type basic ferric sulfate (Fe₈O₈(OH)₆SO₄). The formation of this sulfate-bearing Fe precipitate is consistent with the thermodynamic analysis, the iron mass balance, and a 176% increase in solid-phase sulfur. This neutralizer-free strategy offers a sustainable paradigm for recovering critical metals from iron-rich secondary resources. Full article

Germanium is a critical rare-dispersed metal with irreplaceable applications in infrared optics, fiber-optic communications, and semiconductor industries, making its efficient recovery from secondary resources of great strategic importance. This study investigates the selective recovery of germanium from complex zinc smelting leachates using a novel hydroxamic acid extractant, BGYW, in synergistic combination with P204. The feed solution contained approximately 360 mg/L Ge, 10,790 mg/L Fe²⁺, and 98,530 mg/L Zn, representing a highly complex matrix. Continuous counter-current extraction was performed in a 30-stage miniature mixer-settler. Under optimized conditions of 10% BGYW + 5% P204 in white oil, an O/A ratio of 1:1, and 8 mol/L NH₄F as strippant, the single-stage germanium extraction efficiency reached 99.4%. Over 16 consecutive cycles, the extraction system maintained stable performance with average germanium extraction above 99%. A 3-stage scrubbing section using 50 g/L H₂SO₄ effectively removed co-extracted Zn, Cu, and Al impurities. Iron co-extraction, a major challenge, was successfully mitigated through a 2–3 stage iron scrubbing step using a chloride-containing scrubbing solution, which reduced the iron concentration in the strip liquor from approximately 600 mg/L to below 4 mg/L, and decreased the Fe/Ge mass ratio from 0.197 to below 0.01. The overall germanium recovery across the entire 30-stage continuous process reached 98.82%, and the dissolution loss of BGYW in the aqueous phase was reduced by over 85% compared to the conventional YW100 extractant. Third-phase formation caused by residual organic flocculants from the leaching step was eliminated through enhanced pre-treatment, while ferric fluoride precipitation in the stripping section was resolved by incorporating the iron scrubbing stage. This study demonstrates that the BGYW-P204 extraction system with the integrated iron scrubbing step offers an efficient, stable, and industrially viable approach for germanium recovery from zinc smelting leachates, providing a practical solution to the long-standing challenge of germanium–iron separation and contributing to the sustainable supply of this critical metal. Full article

The complex composition of landfill leachate, characterized by high concentrations of refractory organic matter, ammonium nitrogen, and heavy metals, requires efficient and sustainable treatment technologies. Recently, sludge-based adsorbents (SBAs) obtained from wastewater treatment plants (WWTPs) sludge have emerged as promising alternatives to the conventional activated carbon materials for landfill leachate. This review critically evaluates the recent literature related to the transformation of sludge waste and municipal solid waste-based adsorbents into high-efficiency SBAs as a circular economy strategy for leachate remediation. The correlation of the physicochemical characteristics of landfill leachate with the properties of SBAs to enhance the removal of specific contaminants is discussed. The treatment strategies for landfill leachate including physicochemical, biological, and integration of those are summarized. By correlating adsorption performance with SBAs’s properties and circular economy principles, this review identifies the key knowledge gaps and provides guidance for the development and large-scale implementation of sustainable leachate treatment technologies. Furthermore, the prospects for the application of SBAs in the closed-loop landfill leachate treatment system are addressed. Full article

The leaching behavior of bisphenol A (BPA) remains a significant environmental concern. Despite EU regulatory restrictions and the World Health Organization (WHO) establishing precautionary values for human exposure to this monomer, BPA is still widely used in polymer-based products, including materials for sewer rehabilitation. Standard leaching assessments typically employ deionized water, although natural waters represent actual field conditions. This study investigates the release of BPA and its substitute, bisphenol F (BPF), from an epoxy resin system and a vinyl ester resin system. Sample discs (0.5 cm in height and 11 cm in diameter) were subjected to dynamic surface leaching tests using groundwater and tap water as leaching media. Eluate replacement intervals followed the standardized Dynamic Surface Leaching Test (DSLT; EN 16637-2), marking the first application of natural waters within this standardized test procedure. The detection limit for the gas chromatography analyses was 0.001 µg/L. Compared with the deionized water prescribed by the standard, natural waters resulted in significantly higher cumulative releases of BPA and BPF, with cumulative BPA release increasing by factors of 5.2–9.2 to a maximum of 0.412 mg/m². These findings indicate that the standardized 64-day DSLT may underestimate environmentally relevant emissions and that permissible cumulative release values, derived from modeling and regulatory thresholds, may not be maintained under environmentally relevant conditions. GC–MS screening and the Umu test showed no evidence of genotoxic effects in the leachates. Exploratory analysis suggested a positive relationship between BPA release and pH (R² = 0.79). Overall, the results demonstrate that the choice of leaching medium strongly influences measured emissions and should therefore be reconsidered in assessment frameworks for polymer-based construction materials to better reflect environmentally relevant conditions. Full article

Municipal solid waste landfill leachate represents one of the most environmentally challenging liquid effluents in modern waste management; however, its high nitrogen and phosphorus content renders it a potentially valuable nutrient source for microalgal phycoremediation. Here, Chlorella sp. and Scenedesmus sp. were cultivated for 15 days in CHU-10 standard medium and 50% (v/v) municipal landfill leachate from Nauta, Peru, and characterized across 33 biochemical variables, 14 physicochemical parameters, and 32 metal ions and trace elements. A sequential competitive multivariate pipeline comprising principal component analysis (PCA), hierarchical cluster analysis (HCA), permutational multivariate analysis of variance (PERMANOVA), and linear discriminant analysis (LDA) was applied to both the biochemical and bioremediation datasets. Leachate supplementation increased peak biomass density by 26.6–28.3% and elevated total protein by 56.9% in Chlorella sp. and 73.4% in Scenedesmus sp., while reducing total lipids by 37–46% and suppressing polyunsaturated fatty acid production. Both species achieved net biological removal efficiencies (NBRE) exceeding 86% for ammonium and ammonia; toxic elements, including Cd (~96%), Al (~92%), As (~90%), and Pb (~90%), were removed at higher NBRE than macro- and micronutrient categories. LDA achieved 100% leave-one-out cross-validation accuracy for species classification from both physicochemical and 32-element NBRE profiles. These findings indicate two complementary valorization directions, contingent on further biomass safety verification: leachate-grown Scenedesmus sp. shows a favorable combination of protein enrichment and nutrient removal for single-cell protein production integrated with bioremediation, while Chlorella sp. in standard medium shows a more favorable fatty acid profile for nutraceutical applications. Because leachate-grown biomass also accumulates inorganic and trace-element constituents from the medium, its suitability for protein or nutraceutical use requires direct heavy-metal characterization of the harvested biomass, independent of the demonstrated removal efficiency from the liquid phase. Full article

Rare earth elements (REEs) are critical for advanced manufacturing and clean energy, yet their separation remains extremely challenging due to the nearly identical ionic radii of adjacent lanthanides. Conventional solvent extraction, ion exchange, and precipitation methods are limited by their high reagent consumption, slow kinetics, poor selectivity, and environmental burdens. Nanofiltration (NF) offers a green and efficient alternative—operating in the aqueous phase with low energy demand and continuous high throughput. This review systematically summarizes NF-based REE separation. We first elucidate the fundamental mechanisms (size exclusion, Donnan exclusion, dielectric exclusion, and complexation enhancement), and discuss how lanthanide hydration chemistry underpins these synergistic effects. Membrane materials, from commercial to biomimetic, are critically surveyed, with an emphasis on strategies to overcome the trade-off between permeability and selectivity. The impacts of operating conditions and solution chemistry are analyzed, and NF applications ranging from single REE systems to real leachates are assessed. A comparative evaluation positions NF against conventional technologies. Key challenges remain: poor adjacent REE selectivity, membrane fouling, performance loss at high salinity, chemical instability, and a gap between model and real feeds. Future directions include designing high-selectivity membranes, integrating machine learning optimization, establishing standardized protocols, and realizing closed-loop process integration. Full article

Polyamide nanofiltration (NF) membranes offer a scalable and energy-efficient pathway for lithium concentration from lake brines and battery leachates, but practical implementation hinges on achieving high selectivity of Li⁺ over Mg²⁺. The active layer of these membranes can be positively or negatively charged, carrying both amine groups that can be protonated and carboxyl groups that can be deprotonated with an ionization state that is set by the feed pH. Here, molecular dynamics simulations are used to elucidate how pH-dependent charged functional groups within the polymeric nanostructure of NF membranes govern Li⁺/Mg²⁺ selectivity, arising from electrostatic charge interactions between ions and functional groups at the molecular scale as well as steric size exclusion within the membrane pore structure. Although single-salt Li⁺ or Mg²⁺ feed solutions exhibit similar ion penetration behavior, mixed Li⁺/Mg²⁺ feeds show markedly enhanced Li⁺/Mg²⁺ selectivity at low concentrations when the membrane is positively charged. This selectivity arises because Mg²⁺ interacts more strongly than Li⁺ with repulsive protonated amine (NH₂⁺) groups, suppressing divalent ion transport, an effect that emerges specifically when the two cations compete for the same ${\mathrm{Cl}}^{-}$ ions in a mixed feed. In contrast, for negatively charged membranes, attractive interactions with deprotonated carboxylate (${\mathrm{COO}}^{-}$) groups strongly hinder the transport of both ions, resulting in poor selectivity. Ion clustering within membrane pores further reduces transport through steric effects. These results provide molecular-level insight into how charged functional groups control mono/divalent ion selectivity when competing ions are present and highlight positively charged membranes as optimal platforms for lithium separation applications. Full article

This study explored the utilization of coal gangue with high iron content to synthesize poly-ferric-alum-sulfate (PAFS) and coal gangue leaching residue-PAFS (CG@PAFS) coagulants, which were subsequently applied to treat landfill leachate and its concentrate. The results demonstrated that the PAFS coagulant exhibited notable removal efficiency for key pollutants, including chemical oxygen demand (COD) and total phosphorus (TP), with removal rates of 23.8% and 77.5%, respectively. Its performance was comparable to polyferric sulfate (PFS) and superior to aluminum polysulfate (PAS). Mechanistic investigations revealed that Fe³⁺ in the PAFS coagulant reacted chemically with phosphate ions, forming insoluble precipitates and facilitating phosphate removal through flocculation. Furthermore, PAFS also exhibited moderate removal efficiency for COD and ammonia nitrogen (NH₃-N) via flocculation processes. From a sustainability perspective, this study advances a circular economy model by simultaneously addressing two pressing environmental challenges: the valorization of coal gangue (a massive industrial solid waste) and the treatment of landfill leachate (a hazardous wastewater). Importantly, the post-treatment sludge, rich in available phosphorus and silicon, demonstrates promising potential for beneficial reuse as a soil conditioner, thereby closing the material loop and reducing reliance on virgin chemical resources. This integrated waste-to-resource approach aligns with multiple Sustainable Development Goals (SDGs), particularly SDG 6 (Clean Water and Sanitation), SDG 11 (Sustainable Cities and Communities), and SDG 12 (Responsible Consumption and Production). Overall, this study provides valuable insights into the resource-efficient utilization of coal gangue and presents an effective, low-carbon, and sustainable approach for landfill leachate management. 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 proposes a process combining alkali-activated potassium feldspar, acid leaching, and sol–gel coupling with supercritical drying to prepare high-performance silica–alumina composite aerogel. The optimal parameters for potassium feldspar alkali-melt activation are a calcination temperature of 350 °C, mass ratio of potassium feldspar to sodium hydroxide of 1:1.2, and calcination time of 120 min, achieving an acid-leaching efficiency of 97.3% for the activated potassium feldspar. The acid leachate, using propylene oxide as a gelling promoter, was processed through aging, solvent exchange, and supercritical drying to yield SiO₂-Al₂O₃ aerogel with typical three-dimensional nanoporous network structure. EDS spectroscopy revealed that the spatial distributions of aluminum and silicon elements were highly coincident and uniformly dispersed. XPS and FTIR further confirmed the formation of Si-O-Al bonds, indicating that aluminum atoms were successfully incorporated into the silico-aluminate tetrahedral network, constructing silicon–aluminum composite framework. The SiO₂-Al₂O₃ aerogel exhibits specific surface area of 660.841 m²/g and a pore volume of 1.321 cm³/g. Its mass loss within the 0–1000 °C range is only 9.55%, far lower than the 28% mass loss of pure aluminum oxide aerogel, indicating that the silicon–aluminum composite structure effectively suppresses high-temperature phase transitions and framework collapse. Full article

Coastal riparian zones are important transitional areas for carbon cycling between terrestrial and aquatic ecosystems. However, the associations among litter-derived dissolved organic matter (DOM), soil DOM composition, and soil organic carbon (SOC) fractions across habitats remain insufficiently understood. This study aimed to clarify SOC fraction distribution in woody and herbaceous habitats and evaluate its associations with litter-derived DOM, soil DOM composition, and soil environmental factors in different seasons from a coastal riparian zone. In this study, woody habitats had higher SOC content in March, whereas herbaceous habitats showed greater SOC content in November. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) were generally higher in different habitats. MAOC accounted for a large proportion of the measured SOC-related pools and showed a consistent positive association with SOC content. Soil DOM consisted of protein-like and humic-like components, with herbaceous habitats showing a stronger protein-like component and woody habitats showing a stronger humic-like component in March. Woody litter showed greater DOC and DON release potential than herbaceous litter leachates, while litter-derived humic-like DOM was closely associated with a soil humic-like component. The labile SOC pool was mainly associated with vegetation type and electrical conductivity, whereas MAOC was positively associated with soil moisture content and total phosphorus. Overall, the distribution of SOC fractions in coastal riparian habitats is shaped by habitat-specific environmental factors, including vegetative carbon inputs, litter leaching and soil physicochemical properties. This finding is critical for developing targeted management strategies to facilitate SOC accumulation in coastal zones. Full article

Microbially induced calcium carbonate precipitation (MICP) is a promising biotechnology for environmental remediation; however, the high cost of conventional chemical-grade calcium sources limits its large-scale scalability. This study evaluated the feasibility of utilizing an aqueous extract of natural attapulgite clay as a sustainable, low-cost calcium source for MICP-mediated arsenic (As) immobilization in both aqueous and soil systems. Among the tested minerals, Baiyin attapulgite (group B) exhibited the highest calcium content (62,808.94 mg kg⁻¹) and minimal toxic metal impurities, providing a favorable chemical matrix for biomineralization. At an optimal solid-to-liquid ratio of 1:10, Lysinibacillus fusiformis LF and Enterococcus LZU-1 successfully induced calcite precipitation driven by the attapulgite extract. In batch aqueous remediation experiments (20 days), the attapulgite extract significantly enhanced As removal efficiency compared to the controls; As removal rates peaked at 66.4% for strain LZU-1 (with LZ1 extract) and 65.8% for strain LF (with group B extract), drastically outperforming the standard CaCl₂ groups (31.2–37.3%) and blank controls (21.8–24.5%). Concurrently, soil incubation experiments (30 days) demonstrated that the combined application of attapulgite and MICP bacteria reduced the highly bioavailable exchangeable As fraction from 0.115 to approximately 0.03 mg kg⁻¹, while effectively driving its transformation into more stable carbonate-bound and organic-bound fractions without causing secondary soil salinization. Morphological and mechanistic analyses revealed that, compared to the well-defined euhedral crystals in the CaCl₂ control, the precipitates mediated by the clay extract exhibited distinctly irregular, defect-rich rhombohedral structures. This structural disruption was governed by the natural matrix effect of attapulgite, which simultaneously supplied dissolved Ca²⁺ and provided an abundance of fine clay fragments, calcite micro-grains, and associated amorphous Fe/Al/Mn-bearing phases. These constituents acted as physical scaffolding and heterogeneous nucleation sites that became embedded in the growing CaCO₃ lattice, driving the formation of highly reactive, defect-rich clay-calcite-arsenic composite precipitates that efficiently encapsulated arsenate. Mantel analysis further revealed that the remediation efficiency was significantly correlated with key environmental variables including Ni, V, Ca. These findings highlight the dual-system potential of natural attapulgite as an inexpensive, eco-friendly calcium alternative for sustainable MICP-based remediation of As-contaminated water and agricultural soils. Full article

Tomato production is highly affected by salt stress conditions, especially under protected cultivation systems using low-quality irrigation water. This study assessed the effects of increasing electrical conductivity (EC) levels of the nutrient solution (2, 4, 6, and 8 dS m⁻¹) on growth, biomass distribution, RGB-based spectral indices, physiological traits, petiole sap composition, and leachate chemistry in tomato plants (Solanum lycopersicum cv. Tiny Tim) cultivated in containers within a bamboo nethouse under tropical conditions. The results obtained reported that increasing salinity significantly reduced fresh and dry biomass (61.72 and 61.55% respectively) across all plant organs, with fruits showing the highest sensitivity. Leaf area index (LAI), SPAD values, leaf nitrogen (N) concentration, leaf relative humidity (LRH), and water uptake also declined progressively under saline conditions. In contrast, root and leaf biomass allocation increased under the highest salinity level. Spectral analyses reported reductions in red and blue RGB components and normalized red and blue index values, while normalized green index increased under higher salinity levels. Petiole sap analysis showed a progressive accumulation of sodium (Na⁺) and chloride (Cl⁻) together with reductions in nitrate (NO₃⁻-N) and potassium (K⁺) concentrations, particularly during the reproductive stage. In contrast, °Brix, calcium (Ca²⁺), and phosphorus (P) concentrations increased under salinity, particularly during the reproductive stage. Leachate analyses confirmed salt accumulation in the substrate and reduced plant water uptake. Overall, petiole sap analysis and RGB-based spectral indices provide a rapid, non-destructive, and cost-effective tool for the early detection of salinity stress in tomato, enabling timely irrigation and fertigation adjustments to improve crop performance and resource-use efficiency under saline conditions. Full article