Peroxydisulfate (PDS)-based advanced oxidation processes (AOPs) activated by sludge-based biochar (SBC) hold great promise for antibiotic wastewater treatment. However, pristine SBC suffers from limited active sites and inferior catalytic activity, severely limiting its practical engineering application. In this work, a novel metal-free composite biochar (BPS@SBC) was fabricated via one-step co-pyrolysis of banana pseudostem (BPS) and municipal sludge. The optimized BPS@SBC exhibits excellent synergistic adsorption and catalytic PDS activation performance, achieving 95.5% gatifloxacin (GAT) degradation within 30 min, which far outperforms pure SBC (NA@SBC, 59.3%). Mechanistic investigations reveal that GAT degradation is governed by the synergistic coupling of ˙O2− radical oxidation, 1O2-mediated nonradical oxidation, and electron-transfer pathways. The incorporation of BPS constructs an electron-rich active network containing C–O, C–OH, pyrrolic N, and pyridinic N sites, which accelerates interfacial electron transfer and boosts catalytic performance. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) detection combined with density functional theory (DFT) calculations systematically elucidates the complete GAT degradation pathways. T.E.S.T toxicity assessment verifies that the degradation products exhibit lower aquatic toxicity and weaker bioaccumulation potential than pristine GAT. Furthermore, BPS@SBC possesses excellent anti-interference ability, satisfactory reusability, and robust structural stability, enabling reliable remediation of practical water matrices. This study provides a feasible strategy for the collaborative resource utilization of agricultural and municipal bio-wastes and offers new insights into the design of high-efficiency and stable catalysts for advanced oxidation water treatment.

This study systematically investigated how trace divalent metal cations (M(II): Cu2 +, Zn2+, Cd2+, and Ni2+) affect the precipitation, stability, and phase transformation of hydrous ferric arsenate (HFA) as well as the mechanisms governing As(V) and M(II) mobilization in acidic systems. Natural crystalline ferric arsenate (scorodite) samples from Guangxi, China, validated the environmental relevance of the findings. The results showed that coexisting M(II) slightly inhibited the precipitation of Fe(III)-As(V), and the addition of M(II) promoted the partial dissolution of pre-formed HFA. Density functional theory (DFT) calculations attributed these effects to the site-selective incorporation of M(II) into the HFA chain (Fe1-As1-Fe2-As2) via substitution at the Fe1 site. Aging experiment results (70 °C) revealed that the doping level of M(II) in HFA and secondary scorodite is controlled by a combination of thermodynamics and kinetics. DFT and extended X-ray absorption spectroscopy (EXAFS) results confirmed that the scorodite lattice exerts a thermodynamic screening effect on incorporated M(II). Both Zn2+ and Cd2+ displayed favorable formation energies, whereas Cu2+ and Ni2+ tended toward remobilization. The resulting M(II) incorporation capacities in scorodite follow the order: Zn2+ (15.2 g/kg) > Cu2+ (12.6 g/kg) > Ni2+ (8.3 g/kg) > Cd2+ (3.4 g/kg). This study proposes a kinetic entrapment-thermodynamic screening mechanism for M(II)-As(V) co-immobilization that provides atomic-scale insights into As and M(II) in multi-M(II) acidic waste streams.

This current study explored how the Z-scheme heterojunction photocatalyst was developed by using tubular carbon nitride (TCN) together with carbon dots (CDs) and MIL101(Fe). It extended the range of light absorption to broader spectrum. And it has enhanced the oxidation-reduction ability. This makes the rate of photo-catalytic decomposition of tetracycline hydrochloride in the presence of visible light was significantly higher. In this study, the MIL101(Fe)/CDs-TCN120 exhibits the most significant photocatalytic activity and the highest degradation efficiency of 96.8% for tetracycline hydrochloride. The activity of this combination was greater than that of TCN as there were two times faster degradation rates and five times larger reaction constant ratio. Based on cutting-edge molecular orbital analysis and theoretical calculations, the results show that the surface area of the composite sample accumulates abundant active sites and promotes the generation of reactive oxygen species, which participate in the redox reactions of pollutants, achieving enhanced charge separation and efficient degradation of pollutants. All together, these findings allow establishing solid theoretical concepts on creating effective Z-scheme heterojunction photocatalysts to break down tetracycline hydrochloride.

Herein, a hierarchical S-scheme heterojunction cadmium tungstate/bismuth tungstate induced by interfacial built-in electric field for efficiently enhanced photocatalytic performance was successfully constructed. Owing to the tight contact between cadmium tungstate nanorods and bismuth tungstate nanoflowers, it is demonstrated that the S-scheme heterojunction can be formed, which can efficiently enhance separation and transportation efficiencies of photoiduced charge carriers through an interfacial electric field, thus facilitating the generation of ·O₂- and ·OH radicals. As a result, the optimized CdWO4/Bi2WO6 heterojunction degraded 84% of sulfadiazine (SDZ) within 180 min, and the kobs is 1.62 and 10.2 times higher than pure Bi2WO6 and CdWO4, respectively. Meanwhile, the mineralization efficiency could get 54.39%. Even after four cycles, the degradation efficiency remained at 72.2%. Moreover, through a combination of density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) analysis, the pathways of SDZ degradation involving S-N/N-C cleavage and Smile rearrangement were elucidated. These findings offer insights into the design of efficient S-scheme heterojunctions driven by engineering interfacial built-in electric field for the photocatalytic oxidization of SDZ.

Sludge treatment wetlands (STWs) offer a sustainable alternative for sludge management; however, a comprehensive assessment of their greenhouse gas (GHG) emissions is still required. This study investigated the emissions of methane (CH4) and carbon dioxide (CO2) from three pilot-scale STWs under various seasonal loading cycles. The dynamics of the methanogenic archaeal communities were analyzed. A static transparent chamber was adopted to measure gas emission. The three pilot configurations were an STW1 with PVC vent pipes, an STW2 with PVC vent pipes and reeds, and an STW3 with reeds. Results revealed significant seasonal variations in CH4 and CO2 emission rates, with peaks occurring in summer and troughs in winter. During the loading intervals, the CO2-equivalent emissions (based on CH4) followed the order: STW3 > STW2 > STW1. The installation of PVC vent pipes in STW2 reduced CH4 emissions compared to STW3. Leachate chemical oxygen demand (COD) and volatile solids (VS) content consistently exhibited seasonal trends across all units, with levels descending in the order: spring > winter > autumn > summer. Treatment performance was highest in STW2, followed by STW3 and STW1. STW2 had stronger carbon sequestration capacity than STW3. High-throughput sequencing of the 16S rRNA gene indicated that both plant presence and ventilation reduced the richness and diversity of the methanogenic archaeal communities in the lower sludge layer. Methanobacteriaceae, Methanosarcinaceae, and Methanoregulaceae were identified as the dominant methanogenic families.

Coastal wetlands are increasingly threatened by environmental pollutants, exposing native halophytes to complex abiotic stresses such as salinity, heavy metals, and nutrient overload. Suaeda salsa, a salt-tolerant euhalophyte widely distributed in these regions, has emerged as a model for studying plant adaptations to pollutant stress. This review summarizes recent progress on its physiological and molecular responses to environmental challenges.Pollutant exposure induces the reprogramming of primary metabolism—including carbon, nitrogen, lipid, and organic acid pathways—to support energy production and osmotic homeostasis. Simultaneously, S. salsa activates an antioxidant system comprising enzymatic (e.g., SOD, APX, GR) and non-enzymatic (e.g., ascorbate, glutathione, flavonoids) components to scavenge reactive oxygen species and regulate redox balance. These metabolic processes are modulated by interconnected signaling networks involving hormones (ABA, JA, SA), calcium and ROS signaling, and MAPK cascades. Downstream transcription factors such as WRKY, bZIP, and MYB mediate stress-responsive gene expression.Together, these signaling–metabolism feedbacks constitute an integrated regulatory framework conferring resilience under multifactorial stress. This review also highlights future directions involving multi-omics integration and gene-editing technologies to accelerate the functional exploration and ecological application of S. salsa in phytoremediation and saline agriculture. Core regulatory modules in pollutant stress adaptation of Suaeda salsa.

Porous sludge-based biochar prepared using sewage sludge and aquatic waste as composite precursors can efficiently activate persulfate (PS), achieving the deep degradation of ofloxacin (OFX) in wastewater. Among the three types of aquatic wastes (Aws: oyster shells, OS; crayfish shell, CFS; and crab shells, CS), the incorporation of CS resulted in the sludge biochar (SBC) with the optimal catalytic performance. Compared with the original SBC, the doping of CS significantly promoted the development of the pore structure of the SBC and enriched its surface oxygen-containing functional groups. In comparison with the SBC/PS and NA@CS-SBC/PS systems, the degradation rate of the target pollutant by the CS@SBC/PS system increased by nearly 10 times. This system has a wide pH adaptation range, can maintain efficient degradation performance in the presence of most coexisting inorganic anions, and exhibits excellent cyclic stability and reusability. Mechanistic studies indicated that singlet oxygen (O-1(2)) and superoxide radicals (O-center dot(2)-) are the main active species driving OFX degradation. The evaluation of the toxicity and mutagenicity of the degradation intermediates showed that their hazard levels are equivalent to or lower than those of the parent compound OFX, confirming that the OFX degradation process by the CS@SBC/PS system has no risk of secondary pollution and possesses good environmental sustainability. This study provides a new technical pathway for the resource utilization and high-value conversion of sewage sludge as well as the efficient purification of organic wastewater.

Complex nitrogen pollution in wastewater and the rising energy consumption are calling for the development of coupled advanced technologies to simultaneously remove pollutants and recover energy. Simultaneous nitrification and denitrification microbial fuel cells (SND-MFCs) enable efficient removal of nitrogen and recovery of energy. This review systematically discusses the latest developments of SND-MFC system under different system designs, including reactor configurations, electrode materials, and critical operating parameters that govern the efficiency of the removal of nitrogen and the generation of power. Meanwhile, mechanisms are firstly analyzed from the points of reacting substances, functional zoning and distribution of electrons. This review also describes microbial synergy among nitrifiers, denitrifiers and electroactive taxa from the points of biofilm's stratification, microbial community, strain screening with metagenomic detection and electron-transfer pathways. Furthermore, characteristics of real wastewater of SND-MFC in coking, pharmaceutical, and livestock wastewater are also summarized, exhibiting comprehensive elimination of nitrogen and recovery of bioelectricity under carbon- and aeration-free conditions. Subsequent research should further optimize the performance of the system by developing intelligent strategies based upon machine learning (ML) and digital twin technologies, electrobiological communication circuits, combination of strain screening and gene editing to unlock the full-scale potential of SND-MFC technology. In addition, the transition from laboratory-scale to practical applications also faces multiple technical challenges that require attention.

Sludge-derived biochar (SBC)-activated peroxydisulfate (PDS) is effective for antibiotic wastewater remediation. Nevertheless, pristine SBC suffers from low catalytic activity and poorly defined active sites, which restricts its practical engineering applications. Current studies rarely focus on lignocellulose‑modulated PDS activation by SBC and the corresponding identification of active sites, leaving a critical research gap. Herein, a lignocellulose-rich Xanthoceras sorbifolium Bunge husk (XSH) was adopted to fabricate XSH-doped SBC (XSH@SBC) for doxycycline (DOX) degradation through PDS activation. The optimized XSH@SBC/PDS system achieved 96.6% removal of 30mg/L DOX within 30min, representing a 2.45‑fold improvement compared with the pristine SBC system. Mechanistic results verified that DOX degradation proceeded via a synergistic radical-nonradical pathway, in which ˙O2⁻, 1O2 and electron transfer jointly dominate the reaction. Structural defects, C=O moieties and pyrrolic N acted as pivotal active centers for PDS activation. The system exhibited prominent anion tolerance, robust stability over a pH range of 3–11, satisfactory universality and desirable cyclic performance, and effectively reduced the biotoxicity of DOX degradation intermediates. This work developed a feasible directional modification strategy for SBC, clarified the intrinsic PDS activation mechanism, and provided reliable theoretical and technical support for the engineering treatment of organic wastewater.

Antibiotics in aquatic environments pose severe threats to ecosystems and human health due to their persistent nature and resistance to conventional degradation methods. In this study, a Z-scheme heterojunction comprising silver molybdate (Ag2MoO4) and layered graphitic carbon nitride (g-C3N4) was synthesized via a facile one-pot calcination method, demonstrating enhanced photocatalytic degradation of sulfadiazine (SDZ) under sunlight irradiation. Structural analysis confirmed the successful synthesis of the composite, while photoelectrochemical investigations demonstrated that the synergy between Ag2MoO4 and g-C3N4 significantly enhanced visible-light harvesting and charge carrier separation efficiency, thereby boosting its photocatalytic activity. The optimized 3 wt% Ag2MoO4/ g-C3N4 composite achieved an 81.3 % SDZ degradation efficiency within 3 h. The heterojunction facilitated spatial segregation of photogenerated charge carriers, with holes accumulating in Ag2MoO4 (high oxidation potential) and electrons in g-C3N4 (high reduction potential), thereby minimizing recombination and maximizing redox activity. Recycling experiments confirmed the material's stability, achieving a restored efficiency of 76.2 % through recalcination after four cycles. This work provides a promising strategy for combating antibiotic pollution through advanced material design.

Arsenic-calcium residue (ACR) is a hazardous solid waste generated by the metallurgical industry, posing a significant environmental risk. However, the stability and transformation behavior of ACR in sulfidic conditions remains unclear. Herein, we have investigated the stability and speciation evolution of arsenic (As), sulfur (S), and trace metals during the exposure of ACR to diverse S(-II) concentrations under anoxic conditions at pH of 6 and 11. Our results indicate that environmentally relevant levels of S(-II) (i.e., 1, 10, and 50 mM) significantly enhance the mobilization of As(III) and Cd2+ from ACR, with greater release at pH 6. The main mechanism for the release of As(III) and trace metals from ACR is the reductive dissolution of Ca-arsenate/arsenite and As-trace metals-gypsum. The reductive dissolution of As-trace metals-gypsum leads to the formation of S2O32 & horbar; and SO32 & horbar;. XRD, FE-SEM, FTIR, XPS, and HRTEM analyses reveal that gypsum serves as the host phase for As fixation at pH 6, while calcium-arsenate/arsenite phases predominate at pH 11. Secondary As2S3, CdS, CuS, and symplesite are generated at pH 6, whereas parasymplesite, CdS, and CuS are predominant at pH 11. These results enhance our understanding of the environmental behavior of As, S, and trace metals associated with ACR.

Arsenic-calcium residue (ACR) is a highly hazardous solid waste produced through the lime neutralizationprecipitation treatment of waste sulfuric acid and poses considerable environmental risks. This study proposes a sustainable stabilization strategy for the ACR by utilizing magnetite tailings and carbide slag as sources of iron (III) and neutralizing agents, respectively, to immobilize As in the form of stable scorodite. A pure magnetite reagent was initially used to explore the mechanisms and optimal conditions for As fixation within the ACR through the generation of scorodite. In contrast, magnetite tailings were subsequently employed to validate the technical feasibility of the approach. The XRD, FTIR, and FE-SEM results revealed that scorodite formation is governed by the controlled release of Fe3+ from magnetite. The slow Fe3+ supply modulates Fe-As supersaturation and promotes crystallization into environmentally stable scorodite. The stabilization process using magnetite tailings achieved a high As fixation efficiency of 97.29% in the ACR. Subsequent neutralizationprecipitation with carbide slag further reduced the concentrations of Zn, As, Pb, Cu, and Cd in the residual water to approximately 0.24, 0.28, 0.26, 0, and 0 mg/L, respectively. Both the treated solid residues and the residual water complied with Chinese environmental regulatory standards, demonstrating the industrial applicability of the proposed method. This work offers an efficient, environmentally sustainable, and cost-effective approach for stabilizing hazardous ACR.

Xanthoceras sorbifolia Bunge husks (XSH), a by-product of industrial production, are rich in cellulose, hemicellulose and lignin. The aim of this study was to use XSH as a new type of lignocellulosic feedstock to co-produce high yields of xylo-oligosaccharides (XOS) and glucose via an integrated biorefinery process including hydrogen peroxide presoftening, i.e., H2O2-assisted hydrothermal pretreatment (HHP), liquid hot water (LHW) treatment and enzymatic hydrolysis (EH). The HHP1st-LHW treatment resulted in high selectivity toward hemicellulose, with a minor influence on cellulose and lignin. The maximum XOS (X2-X6) yield of 58.5 % was achieved under optimal conditions, in which the desired functional XOS (X2-X4) was 81.4 %, representing 10.5 g per 100 g of XSH. Moreover, HHP2nd-assisted enzymatic hydrolysis resulted in nearly full degradation of cellulose, and a 102.9 g/L glucose titer corresponding to 95.3 % of the glucose yield was produced via the addition of 10 % glucan (>= 15 % solid loading). Mass balance analysis revealed that 12.9 g of XOS, 38.3 g of glucose and 14.2 g of lignin were produced from 100 g of XSH. These results demonstrated the great potential of XSH as a renewable biomass for high value-added biochemical production. The proposed combined pretreatment method is an environmentally friendly and effective process to for co-produce high yields of desirable XOS, fermentable sugars and native-like lignin.

The coexistence of nitrate and tetracycline antibiotics in groundwater has recently attracted increasing attention. Doxycycline (DOX), a representative tetracycline antibiotic, was firstly selected to evaluate its differential effects on denitrification performance under various C/N ratios. At a C/N ratio of 1.25, the addition of 1.0 mg/L DOX accelerated nitrate reduction, achieving an efficiency of 83.01 % with a nitrate half-life of approximately 40 h. Correspondingly, the electron transport system activity (ETSA) increased by 78 %, while the highest enzyme activities of 1.320 and 450.71 nmol/mg & sdot;min for NAR and NIR, respectively, were observed. These enhancements were attributed to the partial degradation and utilization of DOX by denitrifying bacteria, which promoted electron generation and delivery, thereby improving denitrification performance. Extracellular polymeric substances (EPS) analysis indicated that moderate DOX exposure stimulated additional EPS secretion, which acted as an electron transfer medium to facilitate electron transport. In contrast, under 10 mg/L DOX stress at a C/N ratio of 3.75, nitrate reduction efficiency decreased to 68.11 %, with an extended half-life of 71 h. The abundances of denitrification genes (narG, nirS, norB, and nosZ) and dissimilatory nitrate reduction-related genes (nirB) showed up- or down-regulation trends at different DOX levels. This finding confirmed that DOX exposure altered denitrification pathways by modulating the expression of these genes, thereby affecting nitrate removal efficiency. This study provides a promising strategy for guiding biological nitrate removal under DOX exposure in groundwater environments.

Siderite tailings is a potentially cost-free iron (Fe) source for arsenic (As) fixation in hazardous arsenic-calcium residues (ACR) as stable scorodite. In this study, a pure siderite reagent was employed to investigate the mechanism and optimal conditions for As fixation in ACR via scorodite formation, while the waste siderite tailings were used to further demonstrate the cotreatment method. The cotreatment method starts with an introduction of sulfuric acid to the ACR for As extraction and gypsum precipitation, and is followed by the addition of H 2 O 2 to oxidize As(III) in the extraction solutions and finalized by adding siderite with continuous air injection for scorodite formation. The dissolution-oxidation of siderite can slowly produce Fe(III) to control aqueous As(V)-Fe(III) precipitation supersaturation for continuous scorodite crystallization. Chemical analyses show that the extraction efficiency of As from the ACR reaches 94.55%, while the precipitation yield of extracted As via scorodite formation arrives at 99.63% and 99.47%, leading to fixation efficiency of 94.20% and 94.04% in terms of the total As in the ACR by using siderite reagent and tailings, respectively. The final solid products show desirable TCLP stability and long-term stability, meeting the requirement for safe storage (GB 5085.3-2007). XRD, FTIR, and TEM results reveal that such high stability is attributable to the formation of scorodite and the surface adsorption of As on the raw siderite and secondary maghemite. This innovative and economical application of siderite tailings for the treatment of hazardous ACR can be extended to the management of hydrometallurgical wastes. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

This study explores the enhancement of sludge-derived biochar (SBC) performance through a synergistic coupling of zinc chloride (ZnCl2) activation (ZnAC) and biomass doping for advanced oxidation processes (AOPs). ZnAC significantly increased the specific surface area (SSA), porosity, and functional group (FG) diversity of SBC, leading to improved adsorption and degradation capabilities for pollutants. Biomass doping further enhanced pollutant removal efficiency, with varying effects based on biomass type, as demonstrated by the order CM@SBC > CS@SBC > CH@SBC. The results reveal that ZnAC modifies biochar's microstructure, increasing porosity while hindering graphite carbon formation, whereas biomass doping promotes graphitization and diversifies FGs. Key functional groups, such as quinones, were identified as critical for persulfate (PS) activation, catalyzing the production of reactive oxygen species (ROS) like O-1(2). Furthermore, biochar-derived dissolved organic matter (BDOM) played a pivotal role, with its quinone-rich structure and high content of pyrrole and pyridine nitrogen enhancing PS activation. The catalytic mechanism confirmed that O-1(2) is generated primarily through quinone group catalysis and O-2(-) conversion, highlighting the role of BDOM in pollutant degradation. This research provides a comprehensive understanding of biochar modification mechanisms and offers insights into optimizing its application in sustainable environmental remediation.

Hydrous ferric arsenate (HFA) is a common thermodynamically metastable phase in acid mine drainage (AMD). However, little is known regarding the structural forms and transformation mechanism of HFA. We investigated the local atomic structures and the crystallization transformation of HFA at various Fe(III)/As(V) ratios (2, 1, 0.5, 0.33, and 0.25) in acidic solutions (pH 1.2 and 1.8). The results show that the Fe(III)/As(V) in HFA decreases with decreasing initial Fe(III)/As(V) at acidic pHs. The degree of protonation of As(V) in HFA increases with increasing As(V) concentrations. The Fe K-edge extended X-ray absorption fine structure and X-ray absorption near-edge structure results reveal that each FeO6 is linked to more than two AsO4 in HFA precipitated at Fe(III)/As(V) < 1. Furthermore, the formation of scorodite (FeAsO42H(2)O) is greatly accelerated by decreasing the initial Fe(III)/As(V). The release of As(V) from HFA is observed during its crystallization transformation process to scorodite at Fe(III)/As(V) < 1, which is different from that at Fe(III)/As(V) >= 1. Scanning electron microscopy results show that Oswald ripening is responsible for the coarsening of scorodite regardless of the initial Fe(III)/As(V) or pH. Moreover, the formation of crystalline ferric dihydrogen arsenate as an intermediate phase at Fe(III)/As(V) < 1 is responsible for the enhanced transformation rate from HFA to scorodite. This work provides new insights into the local atomic structure of HFA and its crystallization transformation that may occur in AMD and has important implications for arsenic geochemical cycling.

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Hydrous ferric arsenate (HFA) is a common thermodynamically metastable phase in acid mine drainage (AMD). However, little is known regarding the structural forms and transformation mechanism of HFA. We investigated the local atomic structures and the crystallization transformation of HFA at various Fe(III)/As(V) ratios (2, 1, 0.5, 0.33, and 0.25) in acidic solutions (pH 1.2 and 1.8). The results show that the Fe(III)/As(V) in HFA decreases with decreasing initial Fe(III)/As(V) at acidic pHs. The degree of protonation of As(V) in HFA increases with increasing As(V) concentrations. The Fe K-edge extended X-ray absorption fine structure and X-ray absorption near-edge structure results reveal that each FeO6 is linked to more than two AsO4 in HFA precipitated at Fe(III)/As(V) < 1. Furthermore, the formation of scorodite (FeAsO4·2H2O) is greatly accelerated by decreasing the initial Fe(III)/As(V). The release of As(V) from HFA is observed during its crystallization transformation process to scorodite at Fe(III)/As(V) < 1, which is different from that at Fe(III)/As(V) ≥ 1. Scanning electron microscopy results show that Oswald ripening is responsible for the coarsening of scorodite regardless of the initial Fe(III)/As(V) or pH. Moreover, the formation of crystalline ferric dihydrogen arsenate as an intermediate phase at Fe(III)/As(V) < 1 is responsible for the enhanced transformation rate from HFA to scorodite. This work provides new insights into the local atomic structure of HFA and its crystallization transformation that may occur in AMD and has important implications for arsenic geochemical cycling.