Search Results (1,744)

The fate of heavy metals in agricultural soils is governed by organo-mineral–microbial interactions, which predictive models often fail to capture. The competitive sorption mechanisms of Cd(II) and Cu(II) on montmorillonite/kaolinite composites (Mont/Kao) functionalized with humic acid (HA) and Pseudomonas putida (P. p), a model system representative of contaminated agricultural soils, were investigated. Batch experiments, XRD, FTIR, and thermodynamic analysis reveal that metal retention is a non-additive function of competing interfacial processes. Bacterial biomass dominated sorption, accounting for >50% of total metal uptake, with capacity ranked as: P. p > Mont/Kao-P. p > Mont/Kao-HA-P. p > Mont/Kao-HA > Mont/Kao. Humic acid exerts a dual, concentration-dependent role: Low levels enhanced adsorption via mineral dispersion, while high levels induced surface masking, suppressing bacterial binding sites. Competition was highly asymmetric: Cd(II) reduced Cu(II) maximum adsorption capacity by 75.5% in the Mont/Kao-HA system by preferentially occupying montmorillonite interlayer sites, whereas Cu(II) inhibited Cd(II) below pH 6. Single-metal sorption was characterized by positive ΔS° (32.96–58.89 J·mol⁻¹·K⁻¹), indicative of inner-sphere complexation, while negative ΔS° under competitive conditions signals a transition to outer-sphere complexation. This work provides mechanistic insights into site masking, competitive displacement, and ternary cation bridging controlling metal immobilization in organo-mineral assemblages. Full article

On-demand hydrogen can be generated through methanol steam reforming. Isolated metal atoms hosted on ZnO may provide a lower-cost catalytic platform for this reaction. Density functional theory calculations were applied to examine the complete methanol steam reforming pathways over Ni₁/ZnO and Pd₁/ZnO single-atom catalysts, and the associated kinetics were evaluated using transition-state theory. H₂O and CH₃OH prefer Zn-top sites, with nearly identical adsorption energies on both catalysts, whereas most other intermediates bind more strongly to Pd₁/ZnO as the Pd d-state centroid lies closer to the Fermi level. Formaldehyde (CH₂O) governs product selectivity. The weaker C–3c–O orbital interaction on Ni₁/ZnO favors the direct CO₂-forming pathway without a CO intermediate, for which the rate-determining barrier is 0.844 eV. On Pd₁/ZnO, the CO-mediated and direct CO₂-forming pathways have comparable limiting barriers of 1.152 and 1.190 eV, respectively. The rate constant for the CHO rearrangement required before CO formation is only 6.704 s⁻¹ on Ni₁/ZnO, making CO formation kinetically unfavorable. Taken together, the calculations show that Ni₁/ZnO provides higher intrinsic activity and CO₂ selectivity than Pd₁/ZnO as well as the reference Pt₁/ZnO and Cu₁/ZnO system. This work provides a mechanistic basis for designing efficient single-atom methanol-reforming catalysts. Full article

To address the challenges of weak NO₃⁻ adsorption, insufficient active hydrogen supply, and facile desorption of NO₂⁻ intermediates in neutral electrocatalytic nitrate reduction reaction (NO₃RR), this study employs laser nano-welding technology to fabricate a Ru/WO₃ heterojunction, and constructs a Ru/WO₃/Cu(OH)₂/FC spatially confined electrode using Cu(OH)₂ nanorod arrays as the support. Laser welding achieves metallurgical-grade bonding between Ru and WO₃ while retaining oxygen vacancies in WO₃. Cu(OH)₂ promotes NO₃⁻ adsorption via electrostatic and Lewis acid interactions, and its nanorod array structure confines NO₂⁻ intermediates. In 0.5 M K₂SO₄ + 50 mM KNO₃ electrolyte, the electrode delivers an ammonia yield rate of 16.1 mg h⁻¹ cm⁻² and a Faradaic efficiency of 75.8% at −0.8 V vs. RHE, outperforming control groups. Potential-dependent electrochemical impedance spectroscopy (EIS) confirms that spatial confinement suppresses NO₂⁻ accumulation and optimizes interfacial charge transfer kinetics, providing a new strategy for electrode design in neutral NO₃RR. Full article

The dissociative adsorption of O₂ strongly depends on the activity of CO oxidation electrocatalysts. Using first-principles calculations, we investigated O₂ dissociative adsorption on Cu-, Pt-, and Pd-doped Ag(111) surfaces. Our results show that the adsorption configuration designated t-b-t1 is the most energetically favorable adsorption state, with the O₂ binding strength following the order AgCu(111) > AgPt(111) > AgPd(111) > Ag(111). By analyzing the factors that influence the d-band center, we infer that the ligand effect constitutes the dominant determinant of adsorption behaviour. For the subsequent dissociation of O₂, our calculations identify a viable reaction pathway that begins with the t-b-t1 configuration and evolves into two oxygen adatoms adsorbed at adjacent hollow fcc sites. The computed energy barriers for this pathway follow the order Ag(111) > AgPt(111) > AgPd(111) > AgCu(111). These theoretical findings provide crucial guidance for the practical implementation of Ag-based bimetallic alloys as efficient CO oxidation electrocatalysts. Full article

A Ni/Cu-containing phosphinate material based on 2-carboxyethyl(phenyl)phosphinic acid was synthesized under hydrothermal conditions and characterized using FT-IR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy) and EDAX (Energy Dispersive X-ray Analysis) analysis. The FT-IR spectra suggest the coordination of the phosphinate group to the metal, while SEM revealed compact aggregated particles of the compound. EDAX analysis confirmed the simultaneous presence of both Ni(II) and Cu(II) metals in the synthesized material. DFT (Density Functional Theory) calculations performed on the corresponding mononuclear Ni-CEPPA and Cu-CEPPA models indicated that the Cu complex possesses a smaller HOMO–LUMO energy gap (2.72 eV) than the Ni analog (3.43 eV), suggesting higher electronic reactivity. The obtained material was preliminarily evaluated for Methylene Blue removal, exhibiting an adsorption capacity of 170.24 mg/g. These results suggest that mixed Ni/Cu phosphinate materials may represent potential candidates for adsorption-related applications. Full article

This study presents a comprehensive thermodynamic evaluation of several CO₂ conversion pathways, both non-catalytic and catalyst-assisted, using density functional theory (DFT) calculations in Gaussian 16 (B3LYP/6-311++G(d,p)). In the non-catalyzed section, three key routes are examined: hydrogenation (CO₂ + H₂ → CO + H₂O), dry methane reforming, and the reverse water–gas shift (RWGS). For the hydrogenation reaction, the Gibbs free energy change (ΔG) decreases from +0.018 to +0.005 Hartree as the temperature increases from 298.15 K to 1173.15 K, indicating a slight improvement in feasibility but still a high activation barrier of 0.326 Hartree, underscoring the need for catalysis. Dry methane reforming is both exothermic and spontaneous, with ΔG ≈ = −0.049 Hartree at 298.15 K and −0.030 Hartree at 593.15 K; however, operating under harsh conditions may accelerate degradation of reactor materials. In the catalyst-assisted section, copper surfaces and Cu₃M clusters (M = Sc, V, Ni, Cu, Co and Fe) are evaluated alongside two bimetallic catalysts, Fe₂ and Ni₂, under electrochemical CO₂ reduction (eCO₂RR) conditions. Scandium- and vanadium-doped clusters exhibit significant CO₂ adsorption, as evidenced by shifted vibrational frequencies between 800 and 1800 cm⁻¹ that signal C=O bond weakening. Under the evaluated thermobarometric conditions, Ni₂-containing systems displayed lower Gibbs energy values within their own optimized intermediate set and higher entropy values than the corresponding Fe₂-containing set, suggesting greater configurational flexibility and favorable stabilization trends. However, because Fe₂ and Ni₂ systems are chemically different, absolute total energies were not used as a standalone criterion for intrinsic catalytic superiority. Overall, while some non-catalytic routes become thermodynamically more favorable only at high temperature, the explicit inclusion of catalytic models, particularly doped Cu₃M clusters and Ni-containing systems, indicates enhanced CO₂ activation through stronger catalyst–adsorbate interactions, vibrational weakening of C=O bonds, and favorable electronic descriptors. These results suggest that catalytic systems may enable CO₂ conversion under milder conditions, although full kinetic confirmation requires comparative transition state calculations for each elementary catalytic step. Full article

Copper and lead contamination in loess areas poses a potential threat to soil environmental quality and sustainable land use, while the low permeability, high clay content, and strong buffering capacity of loess often limit the efficiency of conventional electrokinetic (EK) remediation. This study developed an enhanced EK system integrating novel hydrogel (NH) electrodes, a poly(diallyldimethylammonium chloride)-modified activated carbon/carbon fibre (MAC/CF) permeable reactive barrier (PRB), and a vertical voltage for the remediation of Cu- and Pb-contaminated loess. The effects of vertical voltage (0, 10, 20, 30, and 40 V) on EK behaviour, contaminant migration, and removal performance were investigated. The results showed that the MAC/CF PRB improved electrical stability, enhanced electroosmotic transport, and regulated pH evolution by providing conductive pathways and reactive sites for OH⁻ capture and metal adsorption. Compared with the system without a PRB, the accumulated electroosmotic flow (EOF) increased from approximately 680 to 980 mL. The vertical voltage further promoted Cu²⁺ and Pb²⁺ redistribution into the PRB and enhanced the migration–adsorption coupling process. The optimal voltage of 30 V achieved the best remediation performance, with Cu and Pb removal efficiencies of 69–80% and 32–36%, respectively, within 72 h at initial concentrations of 500 mg kg⁻¹. Mechanistic analysis revealed that the vertical voltage transformed the MAC/CF barrier from a passive adsorption layer into an electrically activated migration–capture interface. The synergistic effects of ion transport regulation, OH⁻ buffering, conductive network construction, and heavy metal adsorption effectively suppressed precipitation-induced focusing and improved remediation efficiency. This study provides a promising strategy for enhancing EK remediation of low-permeability and structurally sensitive soils. Full article

One of the main sources of secondary microplastics (MPs) in the marine environment is single-use plastic products. However, research on their adsorption capabilities is still limited. In this study, we used a representative set of well-characterized micro-sized fragments, films, and foam to evaluate differences in copper(II) adsorption via a series of batch adsorption experiments. We aimed to understand how the adsorption capacity of Cu(II) differs between a set of secondary MPs in model seawater. We examined the effect of particle size, surface hydrophobicity, and salinity as factors influencing adsorption. The highest adsorption capacity was observed for foam fragments made from a clamshell PS food container followed by a food tray made from PP (591 ± 168 and 353 ± 45 µg/g of MP, respectively). The presence of a higher salinity environment had no negative effect on the adsorption capacity, except that of spherical PS. Our results suggest that the chosen MPs (hard fragments and films) do not have a high ability for Cu(II) adsorption, except for expanded PS and PP films. This study also highlights the difficulties associated with using irregular pieces of post-consumer plastic in model experiments. Full article

Microplastics (MPs) and potentially toxic elements (PTEs) increasingly co-occur in agricultural and peri-urban soils, yet their combined effects on adsorption, mobility, bioavailability, and phytotoxicity are highly context-dependent. This review synthesizes plant–soil evidence by focusing on the interacting roles of MP polymer type, particle size and shape, aging/weathering state, soil geochemistry, dissolved organic matter, and rhizosphere processes. Across the reported studies, MP-PTE interactions show several major directions of changes: MPs may reduce PTE lability by promoting adsorption, aggregation, or sequestration within coated surfaces and soil aggregates; conversely, they may increase PTE mobility and plant exposure when reversible binding, dissolved organic ligands, pH shifts, or particle transport deliver labile PTEs to root-active zones. Dose-dependent and biphasic responses are also common, with low MP additions sometimes attenuating stress while higher doses intensify toxicity. Quantitatively, available crop studies show that intensified co-exposure can reduce plant biomass by approximately 10.2–29.3%, depending on crop species, plant organ, MP type, dose, and PTE identity, whereas antagonistic or neutral responses are also reported under other exposure conditions. The strongest evidence currently exists for Cd and As, but this review also considers Pb, Cu, Zn, Ni, Cr, and Hg to represent chemically distinct cationic, metalloid, and redox-sensitive PTEs. Overall, MPs should not be treated only as passive contaminant carriers; they act as dynamic reactivity modifiers that can function as sinks, vectors, or indirect regulators of PTE bioavailability depending on soil and rhizosphere boundary conditions. Full article

Copper and its alloys are indispensable for electronics, communications, new energy systems, and aerospace engineering due to their exceptional electrical conductivity and mechanical properties. However, the thin cuprous oxide (Cu₂O) layer that naturally forms on copper and its alloys is prone to failure under elevated temperatures and high humidity, particularly in chloride-rich environments, leading to accelerated localized corrosion. While conventional chromate-based passivation has long been the industrial standard for preventing corrosion, its use has been increasingly restricted by global regulations (such as RoHS and REACH) due to its severe toxicity and health risks. To address the conflict between environmental compliance and protective performance, this review systematically evaluates recent advances in environmentally friendly, chromium-free anti-corrosion coatings in the present review. These alternative coatings are critically analyzed and categorized into four mechanistic groups: (i) inorganic conversion coatings (including molybdate, tungstate, rare earth, and phosphate systems); (ii) organic films formed via chemical or physical adsorption (such as organic inhibitors, thiol-based monolayers, and organosilane self-assembled films); (iii) conversion coatings engineered through covalent bonding, coordination chemistry, and microstructural tailoring; and (iv) multifunctional coatings that integrate self-healing capability with high electrical conductivity. Beyond providing a technical summary, this review explored how the swift progression of electronic information technology, new energy infrastructure, and robotics has imposed more exacting, multifunctional demands on copper components. This review provides a strategic roadmap for future research and prioritizes the creation of protection strategies that operate robustly in multi-physics coupling environments—integrating high conductivity, autonomous self-healing, and long-term chemical stability to ensure the reliability of next-generation infrastructure. Full article

Bacterial colonization and biofilm formation on orthopedic and dental implants remain major clinical complications, while conventional systemic antibiotics are often limited by poor penetration into biofilms and infected bone. These limitations have motivated the development of biomaterials with intrinsic antibacterial activity. Hydroxyapatite (HA), a major inorganic component of bone and teeth, possesses excellent biocompatibility, osteoconductivity, and bone-bonding ability but exhibits limited inherent antibacterial activity. Incorporation of therapeutic metal ions, including Ag⁺, Cu²⁺, Zn²⁺, Ti⁴⁺, Co²⁺, Ga³⁺, Sr²⁺, and Ce³⁺, has therefore emerged as a promising strategy for developing multifunctional HA-based biomaterials. This review critically examines the crystal-chemical basis of metal-ion incorporation into HA and discusses how ionic radius, oxidation state, charge-compensation mechanisms, dopant concentration, and synthesis conditions influence lattice occupancy, physicochemical properties, and biological performance. The antibacterial activity of metal-substituted and metal-modified HA systems generally involves interconnected mechanisms, including bacterial membrane damage, intracellular metabolic disruption, interference with enzymes and nucleic acids, reactive oxygen species (ROS)-mediated oxidative stress, and inhibition of bacterial adhesion and biofilm formation. Ag-, Cu-, Zn-, and Ga-containing HA systems show the most consistently reported antibacterial effects, although their efficacy and cytocompatibility depend strongly on dopant concentration and ion-release kinetics. Co-substituted HA may combine antibacterial activity with angiogenic and osteogenic stimulation, whereas Sr-substituted HA is primarily osteogenic and anti-resorptive, with variable antibacterial performance. Ti-modified HA and TiO₂/HA composites exhibit predominantly photoactive antibacterial behavior, while Ce-substituted HA shows concentration-, oxidation-state-, and synthesis-dependent biological effects. The review also evaluates protein adsorption, osteogenic and angiogenic signaling, macrophage-mediated immunomodulation, biological safety, and representative commercial and translational applications. Overall, metal-substituted HA represents a versatile platform for infection-resistant and regenerative hard-tissue biomaterials, provided that composition, phase structure, ion release, antibacterial efficacy, and cytocompatibility are systematically co-optimized before clinical translation. Full article

In the present work, polyvinylpyrrolidone (PVP) was selected as the primary raw material and fully dissolved in N,N-dimethylformamide (DMF) solvent. Hydroxymethyl cellulose (HMC), acrylic acid (AA) monomer with outstanding chelating performance, and UR were added in sequence. On this basis, composite nanofiber membrane substrates of PVP/AA/HMC/UR were fabricated by means of electrospinning. Afterwards, silane coupling agent KH-560 was blended with polylactic acid (PLA). A uniform PLA/KH-560 functional coating was covered on the surface of the as-prepared nanofiber membrane via microfluidic coating treatment, and the target composite nanofiber adsorbent was ultimately obtained. Relevant performance characterization results indicated that moderate addition of HMC could greatly optimize the tensile strength of the membrane material, whereas excessive HMC dosage would cause a deterioration in mechanical strength. Moreover, the breaking elongation presented a slight declining trend, and the integrated mechanical stability of the membrane could fully meet the service demands for cyclic reuse. As a functional monomer, acrylic acid effectively boosted the material’s adsorption performance toward typical heavy metal ions, including Zn²⁺, Cu²⁺ and Pb²⁺. In simulated acidic wastewater generated from rare earth mining and extraction (pH = 3 and pH = 6.5), the removal efficiency of the as-prepared material for the three heavy metal ions all exceeded 95%. Even after being soaked in strong acid solution at pH 2 for 8 h, its adsorption rate was still maintained at 88.5%. In the cyclic experiment, the adsorption efficiency stayed above 75% after two recycling runs, decreased to roughly 55% in the third cycle, and dropped below 30% at the fourth reuse stage. The introduction of UR imparted remarkable acid-resistant structural stability to the composite material. The membrane structure remained complete without damage after long-term immersion in a pH 2 strong acid environment, and high-efficiency heavy metal removal capability could be guaranteed when the solution pH was not lower than 3. Targeting the practical treatment dilemma of acidic heavy metal-containing wastewater from rare earth exploitation and extraction, this research successfully developed a novel eco-friendly adsorbent featuring superior acid resistance, high adsorption performance and certain recyclability. This newly designed material makes up for the deficiencies in traditional adsorbents represented by activated carbon, including poor heavy metal removal ability in acidic media and secondary pollution risks resulting from disposable use. The research findings can offer a novel technical reference and feasible approach for the purification of acidic rare earth wastewater in practical engineering applications. Full article

Heavy metal wastewater, characterized by high toxicity, poor biodegradability, and strong bioaccumulation potential, poses a serious threat to the ecological environment and human health. Conventional chemical treatment methods are costly and prone to secondary pollution. In contrast, using solid waste to prepare environmental functional materials for “waste control by waste” has emerged as a research hotspot in the field of synergistic water pollution control and resource recovery. This review systematically consolidates the sources, physicochemical properties, and compositional characteristics of typical industrial solid wastes—including red mud, electroplating sludge, fly ash, copper slag, and blast furnace slag—and elucidates how compositional variations constrain the selection of functionalization pathways. On this basis, key preparation techniques, namely hydrothermal synthesis, surface modification/impregnation, thermal treatment, geopolymerization, and sol–gel/polymerization, are critically reviewed and compared in terms of product structural regulation, process complexity, and engineering scale-up potential. Subsequently, the adsorption performance of the resultant materials toward heavy metals such as Pb²⁺, Cu²⁺, Cr(VI), As(VI), Cd²⁺, Ni^2+, and Zn²⁺ is discussed, with particular emphasis on the pronounced effects of pH, temperature, initial concentration, coexisting ions, and adsorbent dosage on adsorption capacity. Notably, Pb²⁺ exhibits the highest adsorption capacity, whereas the removal of Cr(VI) and As(V) is strongly governed by the positive charge density and reduction efficiency of the material surface. In quinary heavy metal competitive systems, marked differences in the affinity of adsorption sites toward distinct metal ions have been observed. Mechanistic analysis identifies ion exchange, surface complexation, electrostatic attraction, and redox reactions as the predominant removal pathways. This review further incorporates engineering-oriented assessments, including multi-component competitive adsorption, fixed-bed column operation, and regeneration stability, and identifies the critical bottlenecks currently impeding the transition from laboratory-scale research to practical implementation—namely, performance instability arising from feedstock variability, attenuation of adsorption capacity during prolonged operation (with a 10–40% decline over 5–10 cycles), underdeveloped regeneration and recovery routes, and a systemic deficiency in techno-economic analysis and life-cycle assessment data. Finally, future research directions are proposed, emphasizing the development of low-carbon and energy-efficient preparation technologies, the promotion of synergistic valorization of multiple solid wastes alongside critical metal recovery, and the advancement of this field toward engineering applications through artificial intelligence-assisted design and life-cycle assessment, thereby furnishing theoretical references and technical support for the integrated management of industrial solid waste resource utilization and heavy metal wastewater treatment. Full article

Biogas slurry can enhance soil fertility, but the heavy metals it contains may pose potential ecological risks to soil-crop systems. To mitigate heavy metal pollution resulting from the application of biogas slurry to soil, this study investigated potential remediation strategies through the use of blended biochar application. In this study, soil incubation experiments were conducted to evaluate the immobilization performance of cow dung biochar (CB), corn straw biochar (SB), and blended biochar (cow dung + corn straw) (C3S7, C5S5, and C7S3) toward Pb, Zn, Ni, Cr, Cu, As, and Cd under different biogas slurry ratios (Z0, Z1:8, and Z1:4). The results concluded that immobilization efficiency consistently followed the order C7S3 ≥ C5S5 > C3S7 > CB ≈ SB, indicating that the blended biochar generally outperformed the two single biochar in the biogas slurry-irrigated soil system. Batch adsorption experiments showed that adsorption of all metals was better described by the pseudo-second-order model (R² > 0.94). Isotherm fitting further indicated that Zn, Ni, Cr, Cu, and Cd were better fitted by the Langmuir model, whereas Pb and As were better fitted by the Freundlich model. Physicochemical characterization, scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS), and Fourier transform infrared spectroscopy (FTIR) analyses collectively suggested that the superior performance of blended biochar was associated with the integration of mineral-related characteristics from CB and surface chemical properties from SB, which together enhanced the synergistic fixation of coexisting metals. Consistently, biochar application reduced the potential ecological risk index (RI) of bioavailable heavy metals in soil, with blended biochar showing lower RI values than CB and SB. C7S3 exhibited the best performance in all treatments, highlighting the potential of blended biochar as an effective amendment for mitigating multi-metal pollution risks with biogas slurry utilization. Full article

The increasing use of nano-agrochemical formulations in agricultural systems has intensified concerns regarding their impact on soil properties and nutrient dynamics. This study aimed to compare the effects of engineered copper (I) oxide nanoparticles (Cu₂O-ENPs) and engineered copper nanoparticles (Cu-ENPs) on chemical and physical properties, as well as on phosphorus (P) availability, in a volcanic soil (VS). Soil samples were incubated for one day with both types of ENPs at a 1% dose under controlled conditions, and changes in pH, electrical conductivity (EC), organic matter (OM), bioavailable copper (Cu), specific surface area (SSA), pore volume (PV) and pore diameter (PD), among other parameters, were evaluated. Additionally, to determine the impact of Cu-based ENPs on P availability, adsorption–desorption studies were conducted using batch systems in triplicate. The findings revealed that both Cu-based ENPs altered the soil’s chemical and physical properties. Notably, both types of ENPs increased the bioavailability of Cu²⁺, with a more pronounced effect observed for Cu-ENPs (720 ± 4.20 mg kg⁻¹), indicating their higher dissolution rates. This phenomenon was associated with an increase in soil EC. Furthermore, Cu-based ENPs decreased SSA and PV, and PD in VS, with a higher effect for Cu₂O-ENPs (SSA = 10.035 m² g⁻¹, PV = 0.009 cm³ g⁻¹, and PD = 3.608 nm). The application of 1% Cu-based ENPs enhanced the adsorption of P in VS at pH = 4.5 and pH = 5.5, with a greater effect observed for 1% Cu-ENPs than with 1% Cu₂O-ENPs. In contrast, 1% Cu₂O-ENPs retained a higher amount of P in VS than 1% Cu-ENPs. Collectively, the results of this study provide novel insights into the contrasting effects of Cu₂O-ENPs and Cu-ENPs in agricultural soils, underscoring the need for further investigation of ENPs to elucidate the underlying mechanisms and the long-term implications for soil health and agricultural productivity. Full article