Search Results (128)

The selective removal of electron-rich emerging organic contaminants (EOCs) from aquatic environments remains a critical challenge, as conventional radical-based oxidation processes suffer from poor selectivity and interference from background constituents. To address this issue, we report an electron-transfer-mediated catalytic oxidation system using peroxydisulfate (PDS) activated by hollow multi-shelled Co₃O₄ (HoMS Co₃O₄) nanoreactors derived from plant-based tannic acid. The triple-shelled hollow architecture affords a high specific surface area with abundant accessible active sites, enabling the HoMS Co₃O₄/PDS system to achieve complete bisphenol A (BPA, 0.04 mM) removal within 90 min (k = 0.045 min⁻¹). Mechanistic investigations, integrating electron paramagnetic resonance spectroscopy, radical quenching, electrochemical analyses and in situ Raman/FTIR spectroscopy, reveal that the degradation proceeds via an electron-transfer-mediated non-radical pathway, in which surface-complexed PDS serves as the primary reactive species. This pathway enables selective oxidation of electron-rich pollutants and endows the system with broad pH adaptability, strong resistance to coexisting water constituents, and robust performance in real water matrices (>93% BPA removal). Moreover, the system maintains stable operation in a continuous flow-through reactor over 72 h with negligible Co²⁺ leaching, offering a sustainable strategy for the selective remediation of EOC-contaminated waters. Full article

Electrocatalytic glycerol oxidation to formic acid (FA) offers a sustainable route for biomass valorization, yet non-noble metal catalysts generally suffer from sluggish C-C bond cleavage and poor product selectivity. Here we report an amorphous nickel–cobalt oxyhydroxide bearing both metal and oxygen vacancies (D-NiCoO_xH_y-V_Cr,O), grown on nickel foam via one-step electrodeposition followed by electrochemical activation with Cr doping. The coexistence of the dual vacancies is experimentally confirmed by X-ray photoelectron spectroscopy (XPS), which reveals elevated Ni³⁺/Co³⁺ ratios and reduced lattice oxygen, and by electron paramagnetic resonance (EPR), which shows a markedly enhanced signal at g = 2.003. Building on prior Cr-leaching approaches in single-metal nickel oxides, this work extends dual-vacancy engineering to an amorphous bimetallic NiCo oxyhydroxide and correlates the defect structure with glycerol-induced interfacial responses, charge-transfer behavior, and product selectivity. The catalyst delivers 200 mA cm⁻² at 1.31 V vs. RHE and achieves 100% Faradaic efficiency for formate at 1.32 V vs. RHE. In situ electrochemical impedance spectroscopy further reveals a significantly reduced charge-transfer resistance. These results establish Cr-assisted dual-vacancy engineering in amorphous bimetallic oxyhydroxides as a promising strategy for selective biomass electrooxidation. Full article

Freeze–thaw cycling can strongly disturb the pore-water environment, soil fabric, and contaminant mobility of heavy-metal-contaminated loess, thereby threatening the long-term effectiveness of stabilization treatments in seasonally frozen regions. This study investigated the coupled hydro-environmental and geotechnical performance of Pb-contaminated loess (untreated control group, CK) treated with microbially induced calcium carbonate precipitation (MICP), graphene (GR)-assisted MICP, and graphene oxide (GO)-assisted MICP under controlled freeze–thaw cycles. One-dimensional consolidation tests, toxicity characteristic leaching procedure (TCLP) tests, zeta-potential measurements, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were conducted to evaluate compressibility evolution, Pb leaching behavior, interfacial electrochemical characteristics, mineralogical changes, and microstructural mechanisms. After 9 days of mineralization, MICP reduced the Pb leaching concentration from 38.05 to 23.00 mg L⁻¹, achieving a 39.55% reduction compared with untreated Pb-contaminated loess. Freeze–thaw cycling increased the susceptibility of treated loess to structural degradation and pore collapse, especially under medium to high vertical stresses. Nevertheless, the void ratio generally followed the order of CK > MICP > MICP + GR > MICP + GO under comparable loading and freeze–thaw conditions, indicating progressively enhanced resistance to compressive deformation. GR-assisted MICP showed an optimum dosage of approximately 1.0%, beyond which Pb leaching increased because of sheet restacking, agglomeration, and non-uniform biomineralization. In contrast, under up to 13 freeze–thaw cycles, GO-assisted MICP maintained the lowest void ratio and the most stable Pb immobilization performance among all treatments, demonstrating improved resistance against freeze–thaw-induced structural degradation. The results suggest that GO-assisted MICP can simultaneously improve Pb leaching control and soil-fabric stability, providing a promising low-carbon strategy for remediating heavy-metal-contaminated loess exposed to water-mediated freeze–thaw disturbance. Full article

Iron oxychloride (FeOCl) has recently attracted considerable attention as a high-performance heterogeneous Fenton-like catalyst. Its layered Fe-O-Cl coordination environment enables rapid FeIII/FeII redox cycling and efficient activation of H₂O₂, thereby promoting the generation of reactive oxygen species (ROS) for pollutant degradation. This review summarizes recent progress in FeOCl-based materials, including their crystal structure, optical, electrochemical, magnetic and other physicochemical properties, synthesis strategies, catalytic mechanisms, and environmental applications, with particular emphasis on experimental evidence and density functional theory (DFT) calculations. Special attention is given to pH-insensitive H₂O₂ activation, visible-light-assisted Fenton-like reactions, heterojunction construction, elemental doping, intercalation engineering, membrane-supported catalysts, morphology engineering, and flow-through electro-Fenton configurations. FeOCl-based catalysts have demonstrated outstanding performance in degrading dyes, antibiotics, phenolic compounds, endocrine-disrupting compounds, and other recalcitrant pollutants, while also showing potential in heavy-metal adsorption, selective oxidation, and energy-related applications. Finally, remaining challenges concerning catalyst stability, iron leaching, scalable synthesis, realistic water matrices, byproduct toxicity, and reactor integration are discussed to guide the rational design of practical FeOCl-based catalytic systems. Full article

Severe electrochemical corrosion and leaching degradation of underground structures are induced by coupled stray current and groundwater in rail transit systems like subways. The microstructural evolution of fly ash geopolymer (FAG) during accelerated leaching was systematically investigated by simulating a coupled direct current (DC) stray current and soft water environment. Pore solution alkalinity and electrolytic cell OH⁻ concentration were utilized as evaluation indicators, combined with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). Results indicate that substantial OH⁻ leaching occurs under the coupled stray-current and soft-water exposure, leading to reduced pore-solution alkalinity and changes consistent with the degradation of the N–A–S–H binding network. Consequently, porosity, most probable pore diameter, and the quantity of harmful pores are increased. However, no obvious changes in the major diffraction peaks associated with quartz and mullite were detected within the resolution of the qualitative XRD analysis. Furthermore, a linearly decreasing trend over time is observed for the coupled leaching rate. Mix proportion analysis demonstrates that FAG leaching resistance is improved by reducing the water-to-binder ratio; specifically, superior gel phase content and pore structure are maintained at a ratio of 0.30. Additionally, cumulative OH⁻ leaching is effectively reduced by decreasing the sodium silicate modulus, with optimal resistance exhibited between 1.0 and 1.2. Concurrently, pore solution alkalinity before and after leaching is significantly elevated by increasing the alkali dosage. This exerts a pronounced inhibitory effect on OH⁻ leaching, thereby substantially enhancing the overall leaching resistance. Full article

The demand for a versatile and portable point-of-use (POU) sensor platform has surged due to the pandemic, especially in countries with limited medical laboratory facilities. We recently unveiled a portable, non-planar, interdigitated, flow-through, porous electrode platform that automatically measures electrochemical impedance spectroscopy (EIS) signals from various biomarkers. However, the packed powder exhibited a loss of performance over time due to displacement, leaching, and poor stability. Herein, we modified the packing strategy by synthesizing the sensing material within the channel, thereby improving adhesion, structural integrity, and stability. Leveraging the exceptional thermal stability, mechanical strength, and chemical resistance of polyimide (PI), we developed a novel fabrication approach that combines liquid-phase inversion and breath-figure techniques to create a porous PI manifold with single-walled carbon nanotubes (SWCNTs) under varying humidity conditions. Scanning electron microscope (SEM) analysis revealed that lower relative humidity (RH) conditions yield larger but less uniformly distributed pores, leading to increased channel pressure. The manifold demonstrated exceptional stability under rigorous flow conditions, withstanding a high flow rate of 30 µL/min while maintaining consistent pressure-EIS responses. The device produced a measurable proof-of-concept impedance response following exposure to a femtomolar concentration of complementary target ssDNA in 1× PBS within 15 min. A formal limit of detection was not determined in the present study. We developed a mechanically stable sensor design with improved durability under repeated flow conditions by systematically optimizing synthesis conditions and manifold configuration. This innovative fabrication strategy demonstrates the importance of packing methodology in sensor design and paves the way for robust, scalable, and efficient diagnostic solutions in resource-limited settings. Full article

The leaching of chalcopyrite in sulfate or chloride media has been proposed to occur through a combined non-oxidative/oxidative mechanism, where H₂S forms an intermediary species, concurrently with direct oxidative leaching. Some studies have noted that elevated concentrations of Cu(II) improve chalcopyrite leaching in sulfate media. In this study, the role of Cu(II) was investigated in the non-oxidative/oxidative process through electrochemical tests on a chalcopyrite electrode, supported by bulk leach tests. The results of the electrochemical tests are consistent with the formation of H₂S through non-oxidative leaching of chalcopyrite. The H₂S subsequently reacts with Cu(II) to form intermediate cuprous sulfide species, which can be readily oxidized by dissolved oxygen. The bulk leach tests point to a synergy between Cu(II) and O₂, further pointing to the catalytic role of Cu(II). The findings support the feasibility of running heap leaching of chalcopyrite-rich ores at elevated copper concentrations in either chloride or sulfate systems. Full article

Gold cyanidation remains one of the most important hydrometallurgical processes in the mining industry. Gold dissolution kinetics and cyanide consumption are governed by coupled anodic–cathodic electrochemical reactions and influenced by pulp pH, particle size, cyanide concentration, mineralogy, and solution chemistry. Despite extensive studies on individual additives in gold cyanide leaching, a coherent synthesis of oxidants and leaching accelerants in modern gold cyanidation remains lacking. The main purpose of this paper is to present a critical review of the literature on leaching accelerants and oxidants used to enhance gold cyanide leaching kinetics and reduce cyanide consumption. The literature highlights that iron sulfide minerals, found in gold ores, can significantly increase cyanide and oxidant consumption through increased oxidant demand, surface passivation, and galvanic interactions that suppress gold dissolution kinetics. This review article summarises the leaching accelerants used, where lead nitrate plays a central role in gold cyanide leaching, and emphasises that its effectiveness is associated with suppression of sulfide-related passivation and favourable modification of surface electrochemistry of gold. The synergistic effects of leaching accelerants with different oxidants on leaching performance are also assessed, with emphasis on their electrochemical roles. Full article

Silicon nanoparticles have attracted considerable attention as high-capacity anode materials for lithium ion batteries. However, the high specific surface area of nanoparticles results in excessive formation of the solid electrolyte interphase, leading to limitations in achieving high energy density. To overcome these limitations, pomegranate-shaped silica microparticles composed of aggregated silica nanoparticles were prepared using ultrasonic spray pyrolysis. Spherical silica nano sols with sizes ranging from 60 to 90 nm were employed as a precursor for the ultrasonic spray pyrolysis, yielding pomegranate-shaped silica microparticles. Subsequent magnesiothermic reduction and acid leaching converted silica into the silicon phase. The resulting silicon microparticles maintained a mean particle size of 2.37 μm with an average internal pore diameter of approximately 30 nm, preserving the structural morphology. Electrochemical evaluation revealed initial charge and discharge capacities of 3179 and 2416 mAh g⁻¹, respectively. After 50 cycles, the discharge capacity stabilized at 500.9 mAh g⁻¹. Full article

Carbon nanotubes (CNTs) serve as exceptional multifunctional supports for metal phthalocyanine (MPc)-based electrocatalysts, effectively addressing the inherent limitations of molecular catalysts such as poor conductivity and aggregation. This review systematically summarizes the recent advances in engineering the interface between MPcs and CNTs to optimize performance in sustainable energy conversion and environmental remediation. We categorize the engineering strategies into three synergistic dimensions: (1) dispersion and modification engineering, introducing the most direct physical anchoring dispersion strategy via non-covalent interactions and targeted modifications to yield highly active catalysts; (2) chemical bonding engineering, in which robust axial coordination or covalent grafting creates stable, well-defined active sites and prevents leaching; and (3) geometric and spatial engineering, which exploits CNTs’ unique curvature, atomic defects, inner cavities and one-dimensional architecture to induce strain, symmetry breaking, and nanoconfinement, thereby steering reaction pathways or to construct conductive nanocomposites. These strategies highlight that CNTs are not merely passive scaffolds but active regulators that geometrically and electronically modulate MPcs. By balancing molecular dispersion, charge transfer, and mass transport, CNT-supported MPcs exhibit superior activity, selectivity, and stability for critical electrochemical reactions, including the oxygen reduction reaction (ORR), CO₂ reduction reaction (CO₂RR), and nitrate reduction reaction (NO₃RR), demonstrating substantial potential for advancing sustainable energy technologies and environmental applications. Full article

Green hydrogen production via water electrolysis is a cornerstone of the sustainable energy transition. However, the oxygen evolution reaction (OER) remains the kinetic bottleneck, limiting overall efficiency. Nickel–iron (NiFe)-based catalysts are among the most promising nonprecious materials for the OER in alkaline media, offering high activity and low cost. Nevertheless, their practical application at industrially relevant current densities (>100 mA cm⁻²) is hindered by several challenges: structural degradation, uncontrolled surface reconstruction, metal dissolution (corrosion), particularly Fe leaching, and the ambiguous role of the fundamental mechanisms. This review critically discusses the current understanding of these degradation pathways, the influence of preparation methods, the interplay between Ni and Fe redox chemistry, and strategies for enhancing long-term stability. Future directions for designing durable NiFe OER electrocatalysts are also outlined. The paper also considers a strategy for investigating new catalysts using electrochemical and non-electrochemical techniques, devoted to young scientists interested in this field. In the Outlook and Perspective section, the key drawback is presented, and a possible strategy for improvement is discussed. Full article

The recycling of spent lithium-ion batteries and selected complex electronic waste fractions is commonly evaluated using isolated metrics such as leaching yield, metal removal efficiency, and reagent consumption. However, this approach fails to address the central challenge of sustainable valorization: integrating upstream conversion with downstream selective recovery without shifting environmental and separation burdens. This review focuses specifically on spent LIBs as the primary model system, while also drawing insights from related e-waste streams (e.g., printed circuit boards and polymer-containing residues) where the interface-driven framework applies. It examines how key interfaces—solid–fluid, polymer–metal–fluid, membrane–solution, electrode–electrolyte, and crystal–solution—govern metal mobilization, selectivity, effluent quality, product purity, and scalability. Emphasis is placed on hydrothermal and supercritical water processing, PVC/CPVC (Polyvinyl Chloride/Chlorinated Polyvinyl Chloride)-assisted metal mobilization and membrane-based recovery techniques, including nanofiltration, membrane distillation, membrane distillation crystallization, ion exchange, and electrochemical methods. Supercritical water and membrane processes are complementary only when upstream chemistry is designed to facilitate downstream separation. PVC-rich waste is reconsidered as a reactive chlorine source, provided that corrosion, HCl formation, and salt precipitation are controlled. Critical gaps include incomplete mass balances, limited multicomponent studies, weak integration between process stages, and scarce techno-economic and life-cycle analyses. A roadmap is proposed for scalable, integrated hydrothermal–membrane systems enabling efficient resource recovery and water reuse. Full article

Pentlandite bioleaching offers a potentially low-energy route for nickel recovery from low-grade sulfide resources, but increasing pulp density may constrain acidophilic microorganisms through metal accumulation, mineral buffering, mass-transfer limitation, and surface-product deposition. This study evaluated pentlandite bioleaching by the nickel-resistant Acidithiobacillus ferriphilus WGS1 at pulp densities of 1%, 5%, and 10% (w/v). Leaching performance and associated interfacial and cellular responses were examined using solution chemistry, mineral and surface characterization, electrochemical measurements under 40 g/L Ni²⁺, and genome-guided transcriptomics. After 30 days at 35 °C, Ni leaching efficiencies reached 99.2%, 97.1%, and 95.7% at 1%, 5%, and 10% pulp densities, respectively, compared with 27.2%, 14.2%, and 0.76% in the corresponding sterile controls. The inoculated systems maintained lower pH and higher ORP than the sterile controls, while the residues showed pentlandite alteration, Ni depletion, secondary Fe-bearing phase formation, and changes in surface sulfur speciation. Under 40 g/L Ni²⁺, the WGS1-containing system showed a lower charge-transfer resistance and a higher corrosion current density than the abiotic system. Transcriptomic comparison between the 10% and 1% pulp-density groups identified 640 differentially expressed genes and highlighted candidate responses associated with Ni homeostasis, Fe/S oxidation, respiratory electron transfer, and energy conservation. Integration of the physicochemical, mineralogical, electrochemical, and transcriptomic results supports a literature-informed working model for WGS1-associated pentlandite bioleaching under high-pulp-density conditions. Full article

Plasticizers enhance polymer flexibility and durability, yet many leach into aquatic environments as persistent contaminants. Phthalate esters (PAEs), the most widely used plasticizers, are of particular concern due to weak polymer binding, high mobility, and documented ecological and human health risks. Conventional analytical techniques such as GC–MS and HPLC provide high accuracy but rely on expensive instrumentation and laboratory-based analysis, limiting rapid and on-site monitoring. In response, electrochemical approaches have emerged as promising alternatives for both the detection and removal of PAEs, especially when coupled with sustainable and environmentally benign materials. This review summarizes recent advances in the electrochemical sensing and treatment of PAEs, highlighting green electrode materials, eco-friendly functionalization strategies, sensing mechanisms, and analytical performance. Key challenges, including matrix effects, environmental interferences, and gaps between laboratory studies and real-sample applications, are critically discussed. Sustainable electrochemical removal strategies—such as advanced oxidation, reductive degradation, and hybrid material-based processes—are also evaluated. Overall, integrating greener materials, molecular imprinting, and data-driven signal enhancement supports the development of robust, field-deployable, and environmentally responsible PAE monitoring and mitigation technologies. Full article

The growing demand for sustainable energy technologies has intensified interest in direct urea fuel cells as an environmentally friendly energy conversion system. In this work, a ternary NiCuZn electrocatalyst is synthesized via a single-step electrodeposition process, offering a rapid and scalable alternative to commonly used hydrothermal or multistep fabrication routes. Structural and compositional analyses (SEM, EDX) confirm the formation of coral-shaped particles of NiCuZn powders. Electrochemical evaluation in alkaline media demonstrates that powders of both tested variants exhibit clear anodic activity, with peak potentials in the range of 0.4–0.6 V_{vs Ag|AgCl (sat. KCl)}. Zinc presence was confirmed also after the process. Upon urea addition, a pronounced enhancement in anodic current density is observed. Notably, variant NiCuZn powder, which was produced using higher current density during electrodeposition, shows superior catalytic activity from approximately 0.4 V_{vs Ag|AgCl (sat. KCl)}, reaching a maximum of 10 mA/cm² near 0.75 V_{vs Ag|AgCl (sat. KCl)}, and stability, which are attributed to its highly homogeneous microstructure and dynamic surface activation mechanism uniquely by partial zinc leaching during operation. These findings demonstrate that electrodeposited NiCuZn systems can deliver competitive performance despite their structural simplicity, highlighting their potential as cost-effective and scalable anode materials for direct urea fuel cell applications. We address a critical bottleneck in fuel cell manufacturing by replacing time-intensive hydrothermal syntheses with a rapid, highly scalable electrodeposition method. Furthermore, the identification of zinc-leaching mechanisms provides crucial new insights into dynamic catalyst activation, moving beyond traditional, static anode designs. Full article