Search Results (404)

The widespread presence of ciprofloxacin (CIP) in aquatic environments threatens ecological and public health, yet conventional treatment processes fail to remove such persistent contaminants. Conventional solvothermal synthesis of Bi-doped g-C₃N₄ photocatalysts involves complicated procedures and low productivity. Herein, we employ a single-step, template-free and solvent-free green calcination method to construct Bi³⁺-modified g-C₃N₄ with strong Bi-N coordination interactions. A series of Bi/g-C₃N₄ photocatalysts with Bi-doping mass ratios of 0.09–0.34 wt% was prepared, and the structure–performance relationship as well as the surface–interface reaction mechanism for ciprofloxacin (CIP) degradation were systematically elucidated. Experimental results confirm that Bi³⁺ incorporates into the lattice via Bi-N coordination bonds with nitrogen in the g-C₃N₄ framework, which narrows the band gap, suppresses photogenerated carrier recombination, and constructs a loose porous morphology beneficial for increasing specific surface area and active sites. Under optimal conditions, 15Bi/g-C₃N₄ achieves 97.6% degradation of 15 mg L⁻¹ CIP within 90 min, which is 13.7% higher than that of pristine g-C₃N₄. The effects of catalyst dosage, initial pH, CIP concentration, common coexisting ions, and different real water matrices on the degradation performance were systematically investigated. Radical quenching experiments combined with ESR characterization confirm that h⁺ is the dominant reactive species responsible for CIP degradation. This green, simple and scalable method yields uniform products, and the resulting materials exhibit high efficiency, economic feasibility and environmental safety, demonstrating promising potential for antibiotic wastewater treatment. Full article

In this study, chicken bone biochar (CBC) was prepared from waste chicken bones via oxygen-limited pyrolysis. A magnetic component (Fe₃O₄) was introduced, and the composite was embedded in a sodium alginate (SA) gel network, successfully constructing magnetic chicken bone biochar/sodium alginate composite gel beads (M-CBC/SA). The experimental results showed that under the conditions of pH = 4.5, 25 °C, and an adsorbent dosage of 0.5 g/L, the removal efficiency of M-CBC/SA toward 50 mg/L U(VI) reached 91.67%, corresponding to an adsorption capacity of 91.67 mg/g. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, with a theoretical maximum adsorption capacity of 322.58 mg/g, indicating that the adsorption was dominated by monolayer chemisorption. The material exhibited excellent magnetic separability and good anti-interference ability against coexisting ions such as K⁺, Na⁺, Cl⁻, and SO₄²⁻, and its adsorption behavior was only weakly affected by ionic strength. Characterization by XRD, FTIR, XPS, SEM-EDS and other techniques revealed that the immobilization mechanism of U(VI) involved the synergistic effects of dissolution–precipitation (the formation of a new autunite phase), surface complexation (involving hydroxyl and phosphate groups), ion exchange (exchange with Ca²⁺), and electrostatic attraction. Using waste chicken bones as the raw material, this composite achieves both efficient uranium immobilization and convenient magnetic separation, fully embodying the environmental concept of “treating waste with waste”, and shows promising application prospects in the treatment of uranium-containing wastewater. Full article

The coexistence of emulsified oil, dissolved organics, and heavy metal ions in industrial oily wastewater makes one-step treatment highly challenging. Herein, an organic-inorganic co-modified PVDF composite membrane (MTSP) was fabricated via nonsolvent-induced phase separation, with tea polyphenols, SiO₂, and fibrous MXene synergistically incorporated. The resulting membrane exhibited a superhydrophilic/underwater oleophobic surface, with a water contact angle of 1° and an underwater oil contact angle of ~136°, owing to the optimized surface chemistry and hierarchical pore structure. As a result, the MTSP membrane effectively suppressed oil fouling while enabling rapid water transport. At 0.1 bar, the optimized membrane delivered an oil/water separation efficiency of ~99.5% and a high flux of 2420–2670 L·m⁻²·h⁻¹, while maintaining >99% separation efficiency for various emulsified oils, including kerosene, edible oil, n-hexane, and 1,2-dichloroethane. It also showed excellent recyclability and chemical stability, retaining >98–99% efficiency after five cycles and after 24 h exposure to pH 1 and pH 12 conditions. Notably, for complex simulated wastewater containing emulsified kerosene, phenol, and Fe³⁺, Cu²⁺, Zn²⁺, and Cd²⁺, the membrane maintained ~99% oil/water separation efficiency and simultaneously removed ~79% of phenol and 70–86% of heavy metal ions in a single filtration process. The superior performance is attributed to the synergistic effects of the superhydrophilic/underwater-oleophobic membrane surface, hierarchical transport channels enabling rapid water permeation, and multifunctional sites that adsorb/coordinate dissolved pollutants. This work provides a simple, scalable design strategy for PVDF-based membranes that integrate high-flux separation, antifouling performance, and multi-pollutant remediation for the treatment of complex oily wastewater. Full article

Urban stormwater runoff often contains toxic metals that threaten aquatic environments. Meanwhile, the large quantities of drinking water treatment residuals (DWTRs) generated worldwide offer opportunities for sustainable reuse as pollutant removal materials. In this study, a manganese sand-modified drinking water treatment residual particle (RDP-M) was prepared from DWTRs and manganese sand for Pb(II) removal from water. Characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) showed that RDP-M had a rough surface morphology and abundant oxygen-containing functional groups, which provided adsorption sites. Batch experiments showed that the maximum Pb(II) adsorption capacity of RDP-M reached 2.79 mg g⁻¹ at 298 K and pH 7.0, which was about 48% higher than that of the unmodified particles (RDP). The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating a chemisorption-dominated process. Thermodynamic analysis further showed that the process was spontaneous and exothermic. RDP-M maintained stable Pb(II) removal over a wide pH range, showed low sensitivity to coexisting ions, and retained high efficiency during repeated use. These results demonstrate that RDP-M has potential as a sustainable granular material for stormwater treatment and waste resource valorization. Full article

In this study, we prepare N–doped biochar loaded with β-CD, using cotton stalks as a carbon source, and evaluate its removal efficiency for tetracycline (TC) and methylene blue (MB) from aqueous solutions. This composite uniquely integrates molten salt activation, nitrogen doping, and β-CD grafting, resulting in an exceptionally high specific surface area of 1943 m²/g and abundant active sites. The findings reveal that β-CD-NKBC-1.5 (5 g of N–doped biochar loaded with 1.5 g of β-CD) demonstrates remarkable capabilities for both TC and MB removal across an extensive pH spectrum, reaching peak adsorption levels of 1269.8 and 969.4 mg/g at 308.15 K, respectively—outperforming most previously reported biochar-based adsorbents. The adsorption process is well described by the pseudo-second-order and Langmuir models, indicating that monolayer chemisorption is the dominant mechanism. β-CD-NKBC-1.5 exhibits preferential adsorption for TC and MB and maintains high adsorption efficiency even with coexisting ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, and SO₄²⁻) at concentrations up to 500 mg/L. The adsorption mechanism involves Lewis acid–base interactions, hydrogen bonding, π–π stacking, and pore filling. Full article

Layered sodium transition-metal oxides are promising cathode materials for sodium-ion batteries due to their high theoretical capacity; however, their practical application is often limited by sluggish Na⁺ diffusion kinetics and structural instability during cycling. P2/O3 phase coexistence has been proposed as an effective strategy to balance capacity and stability, yet it is typically achieved through precise Na-content tuning or complex synthesis conditions, which restrict compositional flexibility. Herein, we demonstrate a phase-engineering approach that induces stable P2/O3 phase coexistence without adjusting the overall Na stoichiometry by controlling the dopant incorporation pathway. Using Na_0.8(Ni_0.25Fe_0.33Mn_0.33Cu_0.07)O₂ (NaNFMC) as a model system, Mg doping via a wet chemical route enables homogeneous dopant distribution, which triggers local stacking rearrangement and the formation of prismatic Na⁺ diffusion channels characteristic of the P2 phase. In contrast, dry-doped samples with identical Mg content retain a predominantly O3-type structure, highlighting the decisive role of dopant incorporation in governing phase evolution. As a result of the phase-engineered P2/O3 coexisting framework, the Mg wet-doped cathode exhibits enhanced initial reversibility, superior rate capability, and improved long-term cycling stability compared to pristine and dry-doped counterparts. Voltage-resolved dQ/dV and cyclic voltammetry analyses reveal stabilized redox behavior with reduced polarization, while electrochemical impedance spectroscopy confirms suppressed impedance growth and improved Na⁺ transport kinetics after cycling. This study establishes that phase engineering through controlled dopant incorporation provides an effective alternative to conventional Na-content tuning strategies for layered sodium cathodes. The findings offer a scalable and versatile design principle for optimizing the electrochemical performance and structural durability of next-generation sodium-ion battery cathode materials. Full article

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

Chitosan, owing to its abundant amino and hydroxyl functional groups, serves as an effective biosorbent for the removal of toxic metal(loid) ions from water. This review summarizes recent advances in chitosan-based adsorbents specifically for arsenate (As(V)) and copper ions (Cu(II)), with an emphasis on adsorption mechanisms and electrospun nanofiber technologies. A conceptual “charge adaptation–structure synergy” model is proposed to elucidate the distinct adsorption behaviors of chitosan toward anionic and cationic substances: under acidic conditions, As(V) adsorption is dominated by electrostatic attraction to protonated amino groups, whereas at pH values near or above the pKa, Cu(II) removal proceeds via synergistic chelation involving deprotonated amino and hydroxyl groups. Competitive and synergistic interactions in binary systems, particularly between As(V) and coexisting anions such as phosphate, are also discussed. Notably, the kinetic advantages of electrospun chitosan nanofibers are highlighted, with equilibrium times shortened from several hours to approximately 0.5–2.6 h. Key challenges and future research directions are further discussed, including scalable manufacturing and the treatment of complex wastewater matrices. Full article

Landfill leachate, a byproduct of municipal solid waste treatment, typically contains hazardous substances such as toxic metals (e.g., lead) and eutrophication agents (e.g., phosphate). This study addresses the pressing challenge of polishing complex wastewater, such as landfill leachate, through the development of a novel ternary layered double hydroxide (LDH). As CaFe-LDHs are known to have an affinity for anions, and CoFe-LDHs have shown an affinity for toxic metal cations, CoCaFe-LDH was proposed to integrate both functionalities. The LDH was anchored on activated biochar to synthetize the novel composite adsorbent CoCaFe-LAB. Key operational parameters (including initial pH, adsorbent dosage, contact time, initial adsorbate concentration, presence of coexisting ions, and regeneration capability) were systematically evaluated. Kinetic and equilibrium analyses revealed that Elovich and Sips models, respectively, best described the adsorption behavior of Pb²⁺ and PO₄³⁻, indicating a heterogeneous adsorption system. Maximum adsorption capacities in synthetic solutions reached 140.81 mg Pb²⁺ g⁻¹ and 25.19 mg PO₄³⁻ g⁻¹ at 45 °C. The CoCaFe-LAB composite proved highly effective, particularly for lead removal. In real effluent tests, the adsorbent achieved complete phosphate removal (100%) from electro-oxidized landfill leachate at a dosage of 2.0 g L⁻¹, confirming its practical applicability and efficiency. Full article

This study reports a sustainable and experimentally simple electrochemical platform for monitoring trace Pb²⁺ using pumpkin peel-derived carbon black (CB) as a modifier on a Nafion-coated glassy carbon electrode (CB/Nafion-GCE). Agricultural waste pumpkin peels were converted into CB, offering a low-cost and environmentally friendly sensing material. CB produced at 650 °C was systematically characterized by SEM, TEM, EDX, XRD, FT-IR, and BET, revealing a mesoporous structure, high surface area, and partial graphitization that enlarged the electroactive area and reduced charge transfer resistance relative to the bare GCE. Under optimized square wave anodic stripping voltammetry (SWASV) conditions, the glassy carbon electrode modified with CB produced at 650 °C (CB650-GCE) exhibited a well-defined linear response towards Pb²⁺ with a limit of detection of approximately 0.19 µM and a limit of quantification of about 0.58 µM, together with good selectivity against common coexisting metal ions. The sensor also achieved satisfactory recoveries in tap and seawater samples, demonstrating its potential as a practical, green analytical tool for routine lead surveillance in environmental waters. Full article

This study investigated the ability of anaerobically digested sewage sludge biochar (ADSSBC), pretreated with nanoscale zero-valent iron (nZVI) prior to anaerobic digestion (AD), to remove lead (Pb(II)) ions from aqueous solutions. Batch adsorption experiments were conducted to evaluate the effects of various parameters, including nZVI dosage, O₂-exclusion method (aluminum foil wrapping or N₂ purging), pyrolysis temperature (300–800 °C), adsorbent dosage, pH, coexisting ions, contact time, and initial Pb(II) concentration. Experimental data were fitted to adsorption kinetic and isotherm models. The characteristics of nZVI30-ADSSBC-700 before and after Pb(II) adsorption were analyzed using FTIR, SEM–EDS, XPS, and XRD to identify the adsorption mechanisms. The results showed that nZVI addition at 30 mg/g-TS prior to AD significantly enhanced Pb(II) removal efficiency compared with the control. Among the investigated pyrolysis temperatures and O₂-exclusion methods, the biochar produced at 700 °C using aluminum foil wrapping exhibited the highest Pb(II) removal efficiency (99.4%) at an initial Pb(II) concentration of 200 mg/L. The maximum Langmuir adsorption capacity obtained for this biochar was 139.3 mg/g. The pseudo-second-order kinetic model best described the Pb(II) adsorption kinetics. The investigated models and the results of physicochemical analyses indicated the involvement of both physical and chemical adsorption mechanisms, including surface precipitation, ion exchange, pore filling, and, to some extent, complexation. Full article

Per- and polyfluoroalkyl substances (PFASs) have raised considerable concern due to their ubiquity, persistence, bioaccumulation, and toxicity. However, cost-effective, high-performance adsorbents for PFAS removal from aquatic environments remain limited. Here, we synthesized a porous graphitic biochar adsorbent (Zn-BBC) from banana peel waste via zinc chloride (ZnCl₂) activation and applied it to removing ten legacy and alternative PFASs from water. Zn-BBC achieved removal efficiencies > 95% for all target PFASs. The adsorption of PFASs onto Zn-BBC followed pseudo-second-order (PSO) kinetics, suggesting chemisorption. Additionally, the adsorption isotherms were well described by the Sips model, indicating surface heterogeneity. Zn-BBC exhibited robust performance over a broad pH range (3–9). Coexisting ions (CO₃²⁻, SO₄²⁻, Zn²⁺, Ca²⁺, and Mg²⁺), tested individually at 10 mM each, had negligible effects on the adsorption of the PFASs examined, except for perfluorobutanoic acid (PFBA). In contrast, humic acid (10 mM) significantly reduced the removal rates of PFBA, perfluorohexanoic acid (PFHxA), and hexafluoropropylene oxide dimer acid (GenX). Nevertheless, in river and lake waters, Zn-BBC achieved >85.0% removal of all PFASs except PFBA. In regeneration experiments, Zn-BBC exhibited excellent reusability. Experimental characterization and density functional theory (DFT) calculations jointly revealed that PFAS adsorption involves electrostatic interactions, hydrophobic interactions, π-CF interactions, surface complexation, and hydrogen bonding. These results suggest that Zn-BBC is a promising sorbent for PFAS removal in water. Full article

Cobalt, a toxic heavy metal frequently present in wastewater, poses serious environmental and health risks but also represents a valuable resource for recovery. This study investigates a novel, environmentally friendly continuous flow in-liquid plasma discharge (CFILPD) system for simultaneous removal of cobalt, zinc, copper, and lead ions from aqueous solutions. The reactor contains two conductive channels where a stable plasma discharge forms between dielectric plates separating opposing electrodes, generating energetic electrons and hydroxyl radicals that react with dissolved metal ions. The effects of varying concentrations (5, 10, 50, and 100 ppm) of zinc, copper, and lead ions on the removal efficiency of 100 ppm cobalt ions were examined under constant conditions: 0.2 L/min argon flow rate, 200 W input power, and 50 mL/min liquid flow rate for 30 min. Results showed that increasing concentrations of co-existing metals significantly inhibited cobalt removal, with the largest reduction (91%) observed in multi-metal systems. Among individual metals at equimolar levels with cobalt, copper showed the strongest inhibitory effect (85% reduction), followed by zinc (53%) and lead (52%). Characterization of the recovered solids revealed cobalt–metal oxide composites (2.5–3 µm), suggesting their potential reuse in technological applications. Full article

Bromine, as a strategic fundamental chemical raw material, is crucial for modern industry, but the traditional chlorine displacement method poses safety risks in oilfield brine development and faces challenges like resource depletion and inefficient utilization. Addressing the need for high-concentration bromine brine development in underground oilfields, this study developed an electrochemical oxidation-based chlorine-free bromine extraction technology. Leveraging the standard redox potential difference between Br⁻ and Cl⁻ (0.271 V), the effective potential window for selective Br⁻ oxidation was determined as 1.0–1.52 V (vs. SHE) via linear sweep voltammetry (LSV). Within this window, efficient and preferential oxidation of Br⁻ over Cl⁻ and OH⁻ was achieved. In simulated brine with high chloride and low bromide concentrations, a Br⁻ conversion rate of 92.3% was attained with no Cl₂ generation. The self-designed zero-gap electrolyzer with carbon cloth as the anode reduced the reaction time by over 75% compared to a traditional H-type cell, oxidizing over 90% of Br⁻ within 12 min. Kinetic studies revealed that the reaction follows first-order kinetics, with current intensity positively correlated with Br⁻ concentration. Investigation of coexisting ions revealed that low concentrations of Cl⁻ promote the reaction, while high concentrations exert inhibitory effects. CO₃²⁻ exhibits a weak promoting effect, and Ca²⁺/Mg²⁺ show negligible impact. Notably, organic matter (e.g., ethylene glycol) concentrations exceeding 80 mg/L substantially compromise bromine recovery efficiency. This technology provides a feasible solution for the safe and green development of high-concentration bromine resources and holds significant importance for the upgrading of the bromine chemical industry. Full article

Urban rivers often contain a complex mixture of contaminants including per- and polyfluoroalkyl substances (PFAS), metals, and various salts. This study aimed to investigate the sediment–water partitioning characteristics of PFAS in urban rivers and analyze the hydrochemical causes of this specific feature. We sampled paired water and sediment samples from urban rivers in a reclaimed water irrigation area in Beijing City. The average total PFAS concentrations in the river water and sediment were 28.44 ± 16.37 ng/L and 6.41 ± 4.20 ng/g dw, respectively. Short-chain PFAS from C4 to C6 and PFCA congeners dominated in the water, while long-chain PFAS above C8 and PFSA congeners dominated in the sediment. The average sediment–water ratio (Log K_d) of PFAS at each site showed an increasing trend with chain length, and was generally higher than that observed in seawater, natural rivers, and lakes, indicating a specific sediment–water partitioning behavior of PFAS in urban rivers. This difference is likely due to the distinct hydrochemical characteristics of the urban rivers, where elevated TDS, the presence of surfactants, and the coexistence of multiple heavy metal ions collectively promote PFAS adsorption onto suspended particulate matter and enhance their accumulation in sediments through sedimentation. Full article