Search Results (458)

The Electro-Fenton (EF) process is a promising technology for the sustainable remediation of organic contaminants in complex wastewater. In this study, a weak magnetic field (~150 G) was applied to enhance the performance of an EF system using magnetite (Fe₃O₄) synthesized by a controlled co-precipitation route as a recyclable solid iron source. The magnetite was characterized by FTIR, SEM/EDS, and XPS, confirming the coexistence of Fe²⁺/Fe³⁺ species essential for in situ Fenton-like reactions. Under the selected operating conditions (90 min reaction time), magnetic-field assistance improved methylene blue decolorization from 14.2% to 46.0% at pH 3. FeSO₄ was used only as a homogeneous benchmark, whereas the magnetite-based system operated without soluble iron addition, minimizing sludge formation and secondary contamination. These results demonstrate the potential of magnetite-assisted and magnetically enhanced EF systems as a low-cost, sustainable alternative for the treatment of dye-containing industrial wastewater and other complex effluents. Full article

Efficient phosphorus recovery is of great significance for sustainable wastewater management and resource recycling. While chemical precipitation is widely used, its effectiveness under complex multi-factor conditions remains challenging to predict and optimize. This study compiled a multidimensional dataset from recent experimental literature, encompassing key operational parameters (reaction time, temperature, pH, stirring speed) and dosages of three metal precipitants (Al³⁺, Ca²⁺, Fe³⁺) to systematically evaluate and benchmark phosphorus recovery performance across these distinct systems, six machine learning algorithms—Random Forest (RF), eXtreme Gradient Boosting (XGBoost), Gaussian Process Regression (GPR), Elastic Net, Artificial Neural Network (ANN), and Partial Least Squares Regression (PLSR)—were developed and cross-validated. Among them, the GPR model exhibited superior predictive accuracy and robustness. ($R^2$ = 0.69, $RMSE$ = 0.54). Beyond achieving high-fidelity predictions, this study advances the field by integrating interpretability analysis with Shapley Additive Explanations (SHAP) and Partial Dependence Plots (PDP). These analyses identified distinct controlling factors across systems: reaction time and pH for aluminum, Ca²⁺ dosage and alkalinity for calcium, and phosphorus loading with stirring speed for iron. The revealed factor-specific mechanisms and synergistic interactions (e.g., among pH, metal dose, and mixing intensity) provide actionable insights that transcend black-box prediction. This work presents an interpretable Machine Learning (ML) framework that offers both theoretical insights and practical guidance for optimizing phosphorus recovery in multi-metal systems and enabling precise control in wastewater treatment operations. Full article

Rubber particles have been proven to have the advantages of improving the energy absorption effect and enhancing the friction between soil particles when used to modify the soil. The rubber-modified soil technology also provides a new solution for the pollution-free disposal of waste rubber. However, when rubber particles are used to modify collapsible loess, they cannot significantly enhance its strength. Previous studies have not systematically clarified whether combining rubber particles with different cementation mechanisms can overcome this limitation, nor compared their shear mechanical effectiveness under identical conditions. In view of this, a dual synergistic strategy is implemented by combining rubber with lime and rubber with enzyme-induced calcium carbonate precipitation (EICP). Direct shear tests and scanning electron microscopy are used to evaluate four modification approaches: rubber alone, lime alone, rubber with EICP, and rubber with lime. Accordingly, shear strength, cohesion, and internal friction angle are quantified. At a vertical normal stress of 100 kPa and above, samples modified with rubber and lime (7–9% lime and 6–8% rubber) achieve peak shear strength values of 200–203 kPa, representing an 86.4% increase compared to rubber alone. Microscopic analysis reveals that calcium silicate hydrate gel effectively anchored rubber particles, forming a composite structure with a rigid skeleton and elastic buffer. In comparison, the rubber and EICP group (10% rubber) shows a substantial increase in internal friction angle (24.25°) but only a modest improvement in cohesion (16.5%), which is due to limited continuity in the calcium carbonate bonding network. It should be noted that the performance of EICP-based modification is constrained by curing efficiency and reaction continuity, which may affect its scalability in conventional engineering applications. Overall, the combination of rubber and lime provided an optimal balance of strength, ductility, and construction efficiency. Meanwhile, the rubber and EICP method demonstrates notable advantages in environmental compatibility and long-term durability, making it suitable for ecologically sensitive applications. The results offer a framework for loess stabilization based on performance adaptation and resource recycling, supporting sustainable use of waste rubber in geotechnical engineering. Full article

Magnetic filaments for fused deposition modeling, 3D printing, were produced by depositing polyamide 11 (PA11), by liquid–liquid phase separation and precipitation, onto exchange-coupled nanocomposite magnetic powders, SmCo₅ + 20 wt% Fe produced by mechanical milling and subsequent annealing. The produced filaments have good mechanical properties, a tensile strength of 32 MPa and a maximum elongation of slightly over 40%. The filaments also present good magnetic properties: a high coercive field of 1 T at 300 K and nearly double the saturation magnetization and remanence, compared to filaments made by depositing PA11 on commercial SmCo₅ and recycled SmCo₅ powders and four times the energy product. This work shows that magnetic filaments made by encapsulating exchange-coupled magnetic nanocomposite powders in PA11 may be a viable option for the production of 3D-printed isotropic bonded magnets, as the high energy product and remanence especially can lead to a reduction in both magnetic powder quantity and rare earth elements required for high performance magnetic filaments. This in turn may reduce costs and improve sustainability. Full article

This study systematically investigates the effects of Fe and Si impurities on the microstructure and mechanical properties of Al-Cu-Li alloys. Five alloy compositions with controlled Fe (0.03–0.12 wt.%) and Si (0.03–0.12 wt.%) contents were fabricated and processed through homogenization, hot extrusion, solution treatment, and aging. Microstructural characterization demonstrates that Fe promotes the formation of coarse skeletal Al₇Cu₂Fe intermetallics, while Si facilitates the precipitation of blocky α-AlFeSi phases and eutectic Si particles. An elevated Fe content substantially deteriorates strength, ductility, and fracture toughness, primarily due to two mechanisms: the persistence of thermally stable impurity phases that serve as stress concentrators and preferential crack initiation sites throughout thermomechanical processing, and the consumption of Cu that reduces the volume fraction of primary T₁ (Al₂CuLi) strengthening precipitates. In contrast, Si exhibits comparatively moderate detrimental effects. The findings establish that stringent Fe control is essential for maintaining mechanical performance, whereas strategic Si adjustment offers a viable approach for cost management in recycled alloy production. Full article

To address the challenges of rutting and performance balance in asphalt pavements under high-temperature and heavy-load conditions, a novel polyolefin composite modifier (PCM-H) was developed from waste tire rubber powder, recycled ethylene vinyl acetate (EVA), acrylonitrile butadiene styrene (ABS), petroleum resin, and polymer additives. The chemical characteristics, thermal stability, and compatibility mechanisms of PCM-H were compared with those of two commercial modifiers (PCM-1 and PCM-2) using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). PCM-H exhibited superior compatibility and thermal stability. In contrast, PCM-2 tends to crystallize and precipitate within the 180–200 °C range, which is detrimental to the stability of the composite system. At an optimal dosage of 10 wt% in styrene–butadiene–styrene (SBS) modified asphalt, PCM-H formed a uniform dispersion and, through crosslinking reactions, established a three-dimensional network structure. Subsequently, the performance of composite modified asphalts, prepared with each of the three modifiers at their respective optimal dosages, was evaluated comparatively. Performance evaluations demonstrated that all polyolefin-modified asphalts significantly outperformed the conventional SBS modified asphalt. The PCM-H modified asphalt (PCM-H MA) exhibited the most superior performance, achieving a performance grade (PG) exceeding 94 °C, along with exceptional high-temperature elasticity and creep resistance, superior low-temperature cracking resistance, and enhanced fatigue healing capability. The results indicated that the crosslinked network structure effectively enhances asphalt cohesion, thereby providing a synergistic improvement in both high- and low-temperature performance. This study provides an effective solution and theoretical basis for developing high-performance pavement materials resistant to high temperatures and heavy loads conditions. Full article

The depletion of natural resources remains a major global challenge, emphasizing the need to develop sustainable processes that enable both metal recovery and waste recycling. This study investigates the leaching of valuable metals from lead smelting slag using methanesulfonic acid (MSA), a biodegradable and environmentally benign reagent. Batch experiments were performed under different MSA concentrations (0.35–1.4 M) and temperatures (22–80 °C). Metal dissolution increased nearly linearly with acid concentration up to 1 M, with maximum recoveries after 60 min of 85% Zn, 64% Pb, 75% Cu, and 68% Fe. Copper dissolution was governed by the oxidation of Cu₂S, while Fe leaching was affected by pH variations that promoted re-precipitation. Kinetic modeling indicated mixed chemical–diffusion control mechanisms, with activation energies of 22.6 kJ mol⁻¹ for Zn and 31–33 kJ mol⁻¹ for Pb, Cu, and Fe. Beyond efficient metal extraction, the process generated a leach residue with reduced concentrations of base metals and a mineralogical composition dominated by stable calcium-silicate phases, improving its potential suitability for reuse in construction or mining backfill applications. Overall, methanesulfonic acid proved to be an effective and sustainable lixiviant, combining high metal recovery with the generation of recyclable slag, thereby contributing to circular metallurgical practices. Full article

The exponential growth of lithium-ion batteries (LIBs) in electric vehicles and energy storage systems has amplified the urgent need for sustainable recycling strategies. Conventional pyrometallurgical and hydrometallurgical methods for LIB recycling are energy-intensive, chemically demanding, and fail to preserve the structural integrity of cath-ode materials. Closed-loop recycling, in contrast, enables the recovery of layered oxides with minimal processing steps, reducing environmental footprint and supporting a circular economy. This study provides a systematic comparison of two regeneration approaches—sol–gel synthesis and hydroxide co-precipitation—for closed-loop recycling of layered NCM (LiNi_xCo_yMn_zO₂) cathode materials recovered from spent LIBs. Spent cells were mechani-cally processed and leached using malic acid to recover Ni, Co, Mn, which were subsequently used to synthesize NCM622 cathode powders. The regenerated materials were characterized using SEM/EDX, XRD, and electrochemical testing in CR2032 coin cells. Both methods successfully produced phase-pure layered oxides with the R-3m structure, with distinct differences in structural ordering and electrochemical behavior. The sol–gel-derived NCM622 displayed higher crystallinity and reduced cation mixing, evidenced by an I(003)/I(104) ratio of 1.896 compared to 1.720 for the co-precipitated sample, and delivered a high initial discharge capacity of 170 mAh/g at 0.1 C. However, it exhibited significant capacity fade, retaining only 60 mAh/g after 40 cycles. In contrast, the co-precipitation route produced hierarchical porous spherical agglomerates that offered superior cycling stability, maintaining ~150 mAh/g after 40 cycles with lower polarization (ΔE_p = 0.16 V). Both materials demonstrated electrochemical performance comparable to commercial NCM. Overall, hydroxide co-precipitation emerged as the most industrially viable method due to scalable processing, compositional robustness, and improved long-term stability of regenerated cathodes. This work highlights the critical influence of synthesis route selection in LIB closed-loop recycling and provides a technological framework for industrial recovery of high-value NCM cathode materials. Full article

The design of novel high-strength (HS), high-electrical-conductivity (HC) and high-thermostability (HT) aluminum alloys is presented utilizing recycled automotive aluminum twitch for cable conductor applications. Calculation of phase diagrams (CALPHAD)-based tools are employed for the design, with key objectives being the enhancement of electrical conductivity through the complete gettering of impurity elements and the optimization of precipitation strengthening through the promotion of Q phase and the suppression of Si phase. The experimental data suggests that thermodynamic equilibrium conditions have not been reached yet under the tested annealing conditions, and models show that Si has the largest impact on electrical resistivity sensitivity. Full article

The Tibetan Plateau (TP), known as the “Asian Water Tower,” plays a critical role in regional and global climate systems. However, water resource sustainability is increasingly threatened under climate change and growing demand. While moisture transport mechanisms for summer monsoon and extreme precipitation events have been widely studied, the understanding of moisture sources for different precipitation intensities remains limited. This study employs the Lagrangian-based HYSPLIT model to quantify moisture source contributions to three types of precipitation events—extreme precipitation (EP), moderate precipitation (MP), and light precipitation (LP)—over the TP from 1979 to 2020. Using trajectory clustering and moisture source diagnostics, we identify dominant transport pathways and their relative contributions. Results show that EP and MP events are primarily influenced by the Indian monsoon, with the Bay of Bengal and Arabian Sea as key sources, while LP events are dominated by westerlies. The western pathway contributes 15.55%, 36.28%, and 59.59% to EP, MP, and LP events, respectively, whereas the monsoon pathway accounts for 40.56%, 28.23%, and 31.21%. External moisture sources dominate across all event types (average 87.7%), with local recycling contributions decreasing from LP (12.90%) to EP (11.55%). These findings enhance the understanding of moisture–precipitation coupling mechanisms over the TP and provide a scientific basis for water resource management under changing climate conditions. Full article

While vanadium-extracted tailings contain valuable components, their utilization is difficult due to their high sodium content. In this work, a new oxygen-pressure calcification and alkaline leaching strategy to achieve barium orthovanadate vanadium precipitation is developed to realize the resourceful recycling and utilization of vanadium-extracted tailings. First, the preparation of barium orthovanadate via calcified alkaline leaching and vanadium precipitation was studied, and the effects of CaO addition, NaOH concentration, leaching temperature, and liquid–solid ratio on the leaching rates of sodium and vanadium were evaluated in single-factor experiments. Under the optimum leaching conditions (CaO addition of 20%, alkali concentration of 150 g·L⁻¹, leaching temperature of 180 °C, and liquid–solid ratio of 10:1), the leaching rates of vanadium and sodium reached 85.25% and 82.36%, respectively. Subsequently, the vanadium-containing leaching solution was subjected to a vanadium precipitation test, and the effects of pH, Ba(OH)₂ addition (expressed as ${\mathrm{n}}_{\mathrm{Ba}}/{\mathrm{n}}_{\mathrm{V}}$), vanadium precipitation temperature, and vanadium precipitation time on the vanadium precipitation rate were investigated. Under the optimum vanadium precipitation conditions (pH 14, ${\mathrm{n}}_{\mathrm{Ba}}/{\mathrm{n}}_{\mathrm{V}}$ = 1.5:1, temperature of 30 °C, reaction time of 60 min), a vanadium precipitation rate of more than 99% was achieved. The precipitated vanadium product of this reaction was confirmed to be Ba₃(VO₄)₂ with a purity of more than 99%. Notably, the wastewater generated during the test process can be mixed with an alkali and returned to the leaching process for reuse, and the dealkalized residue can be used as a raw material for ore reduction in iron smelting processes. Full article

The Muji carbonic springs on the northeastern margin of the Pamir Plateau provide a natural window into tectonically controlled CO₂ degassing within a continental collision zone. Through mineralogical and geochemical analyses, this study constrains the formation mechanisms and regional geological significance of carbonic spring systems. The formed deposits are dominated by calcite and aragonite, with minor dolomite, quartz, and gypsum. The compositions of major elements are consistent with the observed mineral assemblages, reflecting that the carbonate deposition was mainly governed by CO₂ degassing intensity and associated kinetic effects under cold-spring conditions. Carbon isotopes of the deposits are consistently enriched in heavy carbon with δ¹³C values of +3.5‰ to +9.1‰, indicating a persistent contribution of deep-sourced CO₂, most likely derived from metamorphic decarbonation of the crustal carbonates. Calcite exhibits moderate δ¹³C values due to rapid precipitation limiting isotope enrichment, whereas aragonite records higher δ¹³C signatures under subdued degassing and stable hydrodynamic regimes. The narrow δ¹⁸O range (−10.7‰ to −12.6‰), closely matching that of the spring waters, indicates that the tufas record the δ¹⁸O of the spring waters through DIC-water oxygen exchange. Trace element distributions (Sr–Ba–U) reveal systematic enrichment in deep-sourced fluids and progressive downstream geochemical alteration driven by spring–river mixing. The HD springs show high Sr and δ¹³C values, indicating minimal dilution of ascending CO₂-rich fluids, while MJX and MJXSP groups record variable degrees of shallow mixing. Collectively, the Muji system exemplifies a coupled process of “deep fluid input–shallow mixing–precipitation kinetics.” Its persistent heavy δ¹³C and trace-element enrichments demonstrate persistent metamorphic CO₂ release through fault conduits under ongoing compression. These findings establish the Muji springs as a key non-volcanic analogue for deep CO₂ degassing in continental collision zones and provides new insights into crustal carbon recycling and tectonic–hydrochemical coupling at plateau margins. Full article

It is well known that elevated phosphate concentrations in water bodies trigger the eutrophication process, posing adverse environmental, health, and economic consequences that necessitate effective removal solutions. Phosphate removal has therefore been widely studied using various methods, including chemical precipitation, membrane filtration, and crystallisation. However, most of these methods are often expensive or inefficient for low phosphate concentrations. Therefore, in this study, an eco-friendly, sustainable and biodegradable adsorbent was manufactured by extracting calcium ions from an industrial by-product, ground granulated blast furnace slag (GGBS) and magnesium ions from magnesium dross (MgD), then immobilising them on sodium alginate to form Ca-Mg-SA beads. The new adsorbent was applied to remove phosphate from water under different flow patterns (batch and continuous flow), initial pH levels, contact times, agitation speeds and adsorbent doses. Additionally, the degradation time of the new adsorbent, recycling potential, its morphology, formation of functional groups and chemical composition were investigated. The results obtained from batch experiments demonstrated that the new adsorbent achieved 90.2% phosphate removal efficiency from a 10 mg/L initial concentration, with a maximum adsorption capacity of 1.75 mg P/g at an initial pH of 7, a contact time of 120 min, an agitation speed of 200 rpm and an adsorbent dose of 1.25 g/50 mL. The column experiments demonstrated a 0.82 mg P/g removal capacity under the same optimal conditions as the batch experiments. The findings also showed that the adsorption process fitted well to the Freundlich and Langmuir isotherm models and followed a pseudo-second-order kinetic model. Characterisation of Ca-Mg-SA beads using EDX, SEM and FTIR confirmed successful ion immobilisation and phosphate adsorption. Furthermore, the beads fully biodegraded in soil within 75 days and demonstrated potential recycling as a fertiliser. Full article

Polypropylene (PP) is widely used and currently very little recycled. A promising method for recycling the PP present in plastic waste involves its selective dissolution and subsequent separation from undissolved compounds. We address here the fundamentals of PP dissolution. Specifically, we present a model that describes the different phenomena involved in the dissolution of semicrystalline PP and validate the model with the experimental results on the decrystallization and dissolution kinetics of PP pellets. The model provides detailed time-resolved and position-resolved information on composition (i.e., crystalline PP, amorphous PP, and solvent) and solvent diffusivity (which depends on composition) across the dissolving polymer particle, in different solvents and temperatures. Such information is unavailable experimentally or difficult to obtain. The key fitted parameters that capture decrystallization and polymer chain disentanglement decrease with increasing temperature following an Arrhenius relationship, with activation energies higher than that for crystallization and comparable to that for melt viscosity. Both decrystallization and dissolution times increase with particle size. For smaller particles, decrystallization and dissolution occur nearly simultaneously, while for larger particles, their interior remains solvent-poor and crystalline for longer times. This work offers insights into the interplay of decrystallization and polymer chain disentanglement during the time-course of PP dissolution. Further, this work facilitates the design and optimization of a dissolution–precipitation recycling process that can unlock value from the million tons of PP annually that is currently being landfilled or incinerated following its use. Full article

Due to climate change, electromobility and thus lithium-ion batteries are attracting increased interest. With a simultaneous increase in demand for raw materials like Li, Ni, Co, and Mn, their hydrometallurgical recycling is also gaining attention. The associated recoveries must be improved due to EU regulations. In a lab scale, metals are lost to the wrong filter cakes after leaching, cementation, and precipitations. Therefore, this work investigates the question of how many wash steps are suitable after each process step to optimize the recoveries and purity of filter cakes by comparing a reference process and a process with extended washing. The comparison showed that it is possible to recover up to 3.5% of Ni, Co, and Mn by extended washing at each step and in total nearly 100% of Li if wash water is recirculated. An investigation of the substeps of washing demonstrated that single wash steps are able to recover from 0.5% to 3.5% of Ni, Co, and Mn and from 1.6% to 8.7% of Li. The impact of extended washing on purity is shown by the analysis of filter cakes, where the purity of Fe and Al could be improved by 43.0% and for Ni, Co, and Mn by 48.0%. The paper closes with recommendations on how many wash steps are suitable after each process step. Full article