The development of functional hydrogel composites for environmental remediation represents a prominent research direction in sustainable materials science. In this investigation, a hierarchical (GO-g-P4VP/CdSe)@PAA hydrogel was fabricated through a multi-step synthesis protocol. Graphene oxide-grafted poly(4-vinylpyridine)/cadmium selenide (GO-g-P4VP/CdSe) nanocomposite was initially synthesized via facile hydrothermal crystallization, followed by integration into a polyacrylic acid (PAA) matrix through solution-phase crosslinking. The photocatalytic performance evaluation demonstrated that the composite hydrogel exhibited remarkable visible-light-driven catalytic activity. This enhanced degradation efficiency is attributed to the synergistic effects between the P4VP-mediated charge transfer pathways and the GO/CdSe heterojunction structure, which effectively suppresses photogenerated carrier recombination. The three-dimensional (3D) porous hydrogel architecture further promotes reactive oxygen species generation through improved pollutant adsorption-concentration effects and multiple light-refraction events, underscoring its potential for water treatment applications.

Hexavalent chromium (Cr(VI)) is a prevalent heavy metal in electroplating wastewater, known for its high toxicity and carcinogenic properties. Removing Cr(VI) from wastewater is therefore essential. In this study, we coated polystyrene nanospheres (PSNS) with a photoinitiator and successfully grafted poly(hydroxyethyl methacrylate) (PHEMA) onto their surfaces (PSNS-g-PHEMA). We then used epichlorohydrin (ECH) as a cross-linking agent to link PSNS-g-PHEMA and polyethyleneimine (PEI), forming a hydrogel. This hydrogel, featuring polymer chains grafted onto three-dimensional nanospheres providing high-density hydroxyl sites and a PEI network rich in amine groups offering strong electrostatic adsorption and chelation sites, along with a porous structure facilitating rapid mass transfer, demonstrates an exceptional maximum adsorption capacity for Cr(VI) of 779.5 mg/g. This capacity surpasses that of most other adsorbents. The synergistic mechanism involving electrostatic adsorption, reduction, and chelation contributes to this high performance. Furthermore, the adsorption kinetics data were well-fitted by the pseudo-second-order kinetic model, indicating rapid and efficient interaction. Additionally, the material maintained its adsorption performance with minimal degradation after five cycles, indicating its promising potential for efficiently removing harmful Cr(VI) from wastewater.

Chlorine oxide radicals (ClO·) possess excellent application potential for the selective oxidation of ammonia and efficient degradation of organic pollutants. However, it remains challenging to attain high efficiencies for ClO· generation. In this study, a novel photoanode was prepared by anchoring Cl-doped Ru-Co oxide nanoparticles on Sn-doped TiO2 nanowire arrays (Sn-TiO2). Sn doping improved the photocatalytic activity and electrical conductivity of TiO2, and Cl doping optimized the chlorine evolution performance of Ru-Co oxide. Benefitting from these modifications, enhanced ammonia oxidation (96.6%), and ethylenediaminetetraacetic acid removal (99.4%) were obtained synchronously, accompanied by a chemical oxygen demand (COD) removal efficiency of 52.1% and a low NO3--N accumulation of 1.3 mg/L. The toxicity variation during the degradation process was evaluated, and chloramine could be effectively eliminated by appropriately extending the reaction time. The photoanode exhibited excellent application potential for actual electroplating tail wastewater treatment. Experimental results showed that 95.7% of NH4+-N and 89.4% of COD could be degraded within 140 min. Theoretical calculations confirmed that Cl doping enhanced Cl- adsorption on Ru/Co sites, facilitating chlorine evolution. Meanwhile, Sn-TiO2 promoted ·OH generation. Additionally, the inter-wire gaps of the nanowire arrays favored sufficient contact between free chlorine and ·OH. Consequently, the reaction between them was promoted and the generation of ClO· was boosted, ultimately improving pollutant degradation. This study develops a high-efficiency photoanode for enhanced ClO· production, which may contribute to the advancement of photoelectrocatalytic chlorination technology for water remediation.

The photocatalytic water treatment technology has received widespread attention as an efficient and environmentally friendly approach for eliminating antibiotic pollutants in water environments. Polymeric carbon nitride (PCN) is a promising photocatalyst because of its good stability, low cost and facile synthesis. However, the intrinsic defects, such as slow carrier migration and fast recombination of electron-hole pairs, severely limit its practical applications. To improve these issues, a new modification strategy, namely pyrimidine incorporation and molten-salt crystallization engineering, was investigated to synthesize highly crystalline carbon nitride (CryTCN). Pyrimidine incorporation tailored the electronic structure by introducing it-conjugated asymmetry. Molten-salt crystallization promoted the formation of electron-withdrawing C---N groups and improved structural ordering. The dipole moment of Cry-TCN was thus enhanced, facilitating charge carrier separation and electron transport. DFT calculations revealed that the structural evolution markedly strengthened O2 adsorption and reduced the energy barrier for H2O2 generation. The H2O2 production rate by Cry-TCN reached as high as 706.98 mu mol center dot L- 1 center dot h- 1. The yields of H2O2, center dot O2- , and 1O2 by Cry-TCN were 46.27, 5.23 and 6.50 times higher than those by pristine PCN, respectively. Abundant active species enabled Cry-TCN to degrade ciprofloxacin efficiently. Cry-TCN exhibited excellent stability and adaptability in complex water environments. The result of life cycle assessment highlighted the superior environmental friendliness of Cry-TCN throughout its life cycle compared with PCN. This study promotes the development of PCN-based photocatalysts and their application in the photocatalytic water treatment technology.

Electrocatalytic nitrate reduction to ammonia (eNRA) offers a low-carbon alternative to traditional methods and enables simultaneous remediation of nitrate pollution. However, high activity and selectivity in eNRA under near-neutral conditions are hindered by sluggish nitrate activation and the competition of the hydrogen evolution reaction (HER). Tuning interfacial charge redistribution to concurrently regulate nitrate activation and adsorbed-hydrogen (Hads) coverage is feasible to address this dilemma. Herein, a heterointerface electrode of lanthanum-doped Cu3P and CoP (La1CuP/CoP200 C) was prepared via a hydrothermal method and pulsed electrodeposition followed by low-temperature phosphidation. Differential charge-density calculations and Bader charge analysis revealed that La acted as an electron donor and induced charge redistribution at the Cu3P/CoP interface. The electronic modulation strengthened NO3 -adsorption and activation. Meanwhile, La incorporation optimized the Gibbs free energy for H adsorption, thus suppressing the HER while maintaining sufficient Hads for continuous hydrogenation of N-containing intermediates. Consequently, compared with the electrode without La doping, La1CuP/CoP200 C exhibited better eNRA performance, realizing NO3 --N conversion of 95.2%, a Faradaic efficiency of 83.5%, NH4+-N yield rate of 683.8 mu g h-1 cm- 2, and NH4+-N selectivity of 93.9%. In this study, the role of a rare-earth dopant (i.e., La) in the electronic modulation of transition-metal phosphide heterostructure is clarified, and a potential method for efficient nitrate reduction to ammonia is offered.

Wastewater treatment plant (WWTP) discharge has become a focal point in watershed management, and its aggregate impacts on receiving rivers have been preliminarily elucidated. However, the characteristic water quality patterns in receiving rivers under the influence of different WWTP discharges (domestic, mixed, and industrial) remain unclear. To address this gap, water quality indicators were analysed in samples collected upstream and downstream of the outfall during different water periods and characteristic factors were identified. A threshold system for identifying the characteristic water quality patterns was established based on indicator concentration ratios, and the threshold ranges for source-type water quality signature ratios were determined. The characteristic patterns were validated by selecting three characteristic section types (different regions, double outfalls, and long distances). The results showed that the concentrations of most indicators at the downstream of outfalls were 5 % − 70 % higher than those at the upstream, and the water quality index quantified downstream deterioration (0.46 − 0.69). Furthermore, anions and metallic elements were identified as the characteristic factors. Based on these analyses, threshold ranges for source-type water quality signature ratio were determined: domestic (< 6.22), mixed (6.22 − 9.86), and industrial (> 9.86). Validation across the other characteristic sections confirmed that the results were within the threshold ranges. The strength of the indicator interaction by industrial wastewater discharge exceeded that of other wastewaters, thereby elucidating the differential characteristics mechanisms. This study provides a novel methodological framework for watershed water quality characterization, and the established threshold system holds significant practical value for aquatic environment management.

Photoelectrocatalysis is a promising method for removing biorefractory organic pollutants. However, the inefficient utilization of light and electricity by photoanodes and the failure to effectively execute cathode functions typically lead to poor degradation performance. Therefore, in this study, a photoelectrocatalytic (PEC) system coupled with electro-activated persulfate (E-PS) was constructed using a 3D nanostructured PbO2/Sb-SnO2//blue-TiO2//WO3 bifacial anode and a Mo-CuFeO2-modified carbon felt cathode. The results indicate that the bifacial anode could effectively implement electro-assisted photocatalysis on the irradiating side and electrocatalysis on the back side. This significantly accelerated acetaminophen degradation with a synergy index of 48.98 %. Additionally, the PEC/E-PS system was established by combining a bifacial anode with a persulfate-activated cathode, which promoted the efficient utilization of photogenerated electrons and increased the number of active species in the coupled system. Density functional theory calculations confirmed that Mo tended to dope the Fe sites and promote the adsorption of PS on Mo-CuFeO2, facilitating the continuous activation of persulfate. In the coupled system, the contribution order of different active species to acetaminophen degradation was h(+) > OH > SO4- > O-1(2) > O-2(-). Their mutual conversion enabled the PEC/E-PS system to efficiently remove acetaminophen with a relatively high current efficiency (22.69 %) and low energy consumption (0.06 kWh & sdot;gCOD(-1)). The proposed PEC/E-PS system is an efficient and sustainable method for treating organic contaminants in wastewater.

Modulating the adsorption of nitrate ions and intermediates is an effective strategy to enhance the electrocatalytic performance on the conversion of NO3- to NH3. Here, a Cu1Ni1/NiFeP/Nickel foam (NF) nanosheet array electrode with heterointerfaces was designed and synthesized to achieve high-performance nitrate reduction to ammonia (NRA). The interfacial charge polarization at the heterointerface between CuNi and NiFeP induces an electron deficiency on the Cu surface, enhancing the adsorption of nitrate ions. Experimental and theoretical calculations confirmed that Cu sites regulate the adsorption of nitrate ions and intermediates during NRA, whereas Ni and NiFeP sites facilitate the dissociation of water molecules and provide *H to Cu sites on demand. Owning to the combination of Cu, Ni, and NiFeP tandem catalytic sites, Cu1Ni1/NiFeP/NF exhibited a significant synergistic effect with a synergy index of 60.0 %. When the initial NO3--N concentration was 100 mg L-1, the NRA performance of Cu1Ni1/NiFeP/NF (NO3--N conversion: 98.9 %, Faradaic efficiency: 94.0 %, NH3-N yield: 537.0 μg h-1 cm-2, and NH3-N selectivity: 87.3 %) significantly outperformed that of the Cu1Ni1/NF and NiFeP/NF electrodes. This study elucidates the mechanism of the enhanced NRA process at the Cu1Ni1/NiFeP heterointerface, and provides an efficient and sustainable approach for treating nitrate-containing wastewater.

Hydrometallurgy recycling of heavy metals from electroplating sludge is of hot spot in recent decades. Such recycling was tedious in the separation of impure Fe/Al prior to heavy metals from acid leachate after sludge dissolution. Herein, a facile hydrothermal route was developed to separate Fe/Al from Cu-bearing leachate. The results showed that when the leachate was directly hydrothermally treated at 160 °C in the presence of nitrate and ethanol, Al/Cu were stable in the leachate, but nearly 100

Antimony is a highly poisonous pollutant that needs to be removed from water to ensured safety. In this work, we have fabricated a novel adsorbent, the ferric-manganese oxide (FeMnO x ) nanoparticles embedded cellulose nanocrystal-based polymer hydrogel (FeMnO x @CNC- g-PAA/ q P4VP, denoted as FMO@CP q P), specifically engineered for the remediation of antimony-laden water. Comprehensive evaluations have been conducted to investigate the efficacy of the FMO@CP q P hydrogel in removal of antimony from water. The hydrogel exhibits superior affinity for antimony, with maximum adsorption capacities of 276.1 mg/g for Sb(III) and 286.8 mg/g for Sb(V). The adsorptive dynamics, governed by the kinetics and isotherm analyses, elucidate that the immobilization of both Sb(III) and Sb(V) is facilitated through a homogeneous and monolayer chemisorption mechanism. The hydrogel has a three-dimensional interconnected porous structure and exhibits good swelling behavior, which facilitates the rapid absorption of antimony ions by this high surface area hydrogel into the channels. Furthermore, various effects, including the oxidation and inner-sphere coordination mediated by FeMnO x NPs and the electrostatic attractions of the quaternized P4VP chains, promote the immobilization of antimony species. Owing to its high removal efficiency, stability and reusability, the FMO@CP q P hydrogel emerges as an exemplary candidate for the removal of antimony contaminants in water treatment processes.

A cellulose nanocrystal (CNC) polymer hydrogel containing magnetic iron oxide nanorods (Fe3O4NRs) was prepared for As(III) removal in water. Systematic studies on the performance of these prepared CNC-based composite hydrogels for the removal of As(III) have been undertaken. The maximum adsorption capacity of the CNC-g-PAA/qP4VP (CPqP) hydrogel was 241.3 mg/g. After introduction of Fe3O4NRs in the hydrogel, the maximum adsorption capacity of the resulting Fe3O4NRs@CNC-g-PAA/qP4VP (FN@CPqP) hydrogel was further improved to 263.0 mg/g. The high adsorption performance can be attributed to the facts that the 3D interconnected porous network of the hydrogel allows As species to easily enter into the hydrogel, the quaternized P4VP chains provides more adsorption sites, Fe3O4NRs uniformly distributed in the internal cavity of the hydrogel significantly reduces the nanoparticle aggregation. The adsorption kinetics indicated that the adsorption of arsenic by the hydrogel was mainly chemisorption. The isotherm analysis revealed that the adsorption of arsenic by the hydrogel was principally monolayer adsorption on a homogeneous surface. Moreover, the asprepared CNC-based polymer hydrogels exhibited good stability and reusability with negligible performance loss after five adsorption-desorption cycles. The novel FN@CPqP hydrogel demonstrates great potential as a costeffective adsorbent for the removal of arsenic contaminants from wastewater.

In this research, we established an enhanced aerobic biological method utilizing a high-density bacterial flora for the treatment of low-biochemical plating parts washing wastewater. The elucidation of pollutant removal mechanisms was achieved through a comprehensive analysis of changes in sludge characteristics and bacterial community structure. The results demonstrated that throughout the operational period, the organic load remained stable within the range of 0.01-0.02 kgCOD/kgMLSS & sdot;d, the BOD5/COD ratio increased from 0.004 mg/ L to 0.33 mg/L, and the average removal rates for key pollutants, including COD, NH4+-N, and TN, reached 98.13%, 99.86%, and 98.09%. MLSS concentration remained at 7627 mg/L, indicating a high-density flora. Notably, Proteobacteria, Bacteroidota, and Acidobacteriota, which have the ability to degrade large organic molecules, had been found in the system. This study affirms the efficacy of the intensive aerobic biological method for treating low-biochemical plating washing wastewater while ensuring system stability.

Oxidizing ammonia to nitrogen is a challenge in wastewater treatment. For this challenge ammonia oxidation via chlorine oxide radicals has been proved to be a potential method. In this study, a space-confined photoanode was designed and prepared by loading RuO2 nanoparticles on TiO2/WO3 nanowires for in situ enhancing the generation of chlorine oxide radical. Scanning electron microscopy characterization confirmed that RuO2 nanoparticles were uniformly deposited on TiO2/WO3 nanowires. The generation of chlorine oxide radical was markedly boosted, and its steady-state concentration reached 2.76 x 10- 12 M. This value was 3 times that of the traditional bifacial electrode (a type of electrode that has been widely used for chlorine oxide radical-related research). As a result, ammonia oxidation was greatly enhanced. In 90 min, 31.9 mg/L ammonia nitrogen could be degraded, yet only 0.94 mg/L nitrate was accumulated. In addition, the space-confined photoanode exhibited good performance for real wastewater treatment, and 41.0 mg/L ammonia nitrogen could be oxidized in 135 min. During photoelectrocatalysis, a synergistic index (47.7 %) was obtained. Besides the synergistic effect between photocatalysis and electrocatalysis, the unique morphology and structural design (TiO2/WO3 and RuO2 were mainly responsible to hydroxyl radical generation and free chlorine production, respectively) also synergistically promoted the generation of chlorine oxide radical, thereby improving ammonia oxidation. The mechanism for ammonia oxidation via chlorine oxide radicals over the space-confined photoanode was proposed based on experimental results and theoretical calculations.

From the perspectives of environmental protection and resource reclamation, the electrocatalytic reduction of nitrate not only removes nitrate but also converts it into value-added ammonia. In this study, a galvanostatic deposition method was used to prepare a dendrite-like CuNi substrate, on which Cu, Pd, and Fe were co-deposited by pulse electrodeposition to fabricate a ternary alloy electrode for the highly efficient reduction of nitrate to ammonia. The physicochemical properties of the synthesized materials were characterized in detail by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical tests. The results indicated that, benefiting from the dendritic substrate, the electrochemically active surface area of the ternary alloy electrode increased by 1.65 times. Under optimal conditions (applied potential -1.6V (vs. SCE); pH 7), the removal efficiency of NO3--N (100mgL-1) over the C3P1F1 electrode reached 98.9% in 180min. The selectivity of NH3-N and its yield were 83.1% and 309.5μgh-1 cm-2, respectively. The faradaic efficiency was 83.7%. Based on the experimental results and theoretical calculations, it is believed that the enhanced adsorption of NO3- to the ternary alloy electrode surface is one of the reasons for the improvement in electrocatalytic nitrate reduction. In addition, * H-capturing experiments clarified the important role of *H in nitrate reduction.

Recovery of valuable vanadium (V) from V-rich waste was of economic and environmental and commonly treated by calcination and/or extraction. Herein, a novel route was developed to stepwise separate Fe and V from grayish slag via a coupled dissolution and hydrothermal route. After dissolving the V-rich slag in acid, the generated leachate was hydrothermally treated with the addition of phosphate and ethanol. 99.1 % Fe was effectively removed, whilst the loss of V and Mg were only 5.2 % and <2 %. The optimal parameters were 160 C-degrees, 20 g/L phosphate and 0.1-ml ethanol. Fe reacted with phosphate and crystallized as phosphosiderite particles at 160 C-degrees. With the Fe removal, free H+ was released and then consumed in the redox reaction of nitrate and ethanol. The thermodynamic analysis showed that phosphate accelerated the Fe hydrolysis/crystallization, resulting in the removal of Fe prior to V at the pH < 0.5 and the co-removal of Fe/V at the pH > 1. 98.7 % V was recycled as vanadium oxide hydrate particles by adjusting the leachate to pH 0.2 at 90 C-degrees by adding urea. This provided as a promising strategy to separate Fe and V from leachate and posed potential application in the resource utilization of V-rich waste.

To simultaneously remove organic carbon and nitrogen, especially from wastewater containing organic amine compounds, a nanotube photoanode was prepared by depositing RuO 2 and BiVO 4 nanoparticles in and on a blue TiO 2 nanotube substrate (BTNT/RuO 2 /BiVO 4 ). The synthesized materials were systematically characterized by scanning electron microscope, energy -dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical tests. Acetaminophen, a commonly used pharmaceutical with an amine group, was used as the model pollutant to examine the performance of the prepared electrodes. The results indicated that acetaminophen could be degraded by 100 % in 180 min over BTNT/RuO 2 /BiVO 4 with a rate constant of 0.0338 min -1 , which was 25.0 and 1.1 times higher than those obtained over BTNT/BiVO 4 and BTNT/RuO 2 , respectively. Meanwhile, 81.3 % of total nitrogen could be removed. Compared with BTNT/BiVO 4 and BTNT/RuO 2 , BTNT/ RuO 2 /BiVO 4 had a significant synergistic effect, and the synergy index reached to 47.7 %. Additionally, BTNT/ RuO 2 /BiVO 4 exhibited good stability, high current efficiency (63.2 %) and low energy consumption (0.020 kWh.g COD -1 ). The good performance of BTNT/RuO 2 /BiVO 4 was mainly attributed to the enhanced formation of ClO. resulted from the synergistic interaction between RuO 2 and BiVO 4 due to the spatial confinement effect. Lastly, a possible reaction mechanism via ClO. over BTNT/RuO 2 /BiVO 4 was proposed.

Spent lithium battery is a polymetallic waste, and valuable to be recovered as Li-bearing chemical with the barriers of impurities separation, especially Fe and Al. Here in, Li-rich cathode powder was manually disassembled from spent battery, and then recovered as lithiophosphate plate in consideration of effective separation of impure Fe/Al. The powder comprised of 23.2% Fe, 3.2% Al, 5.5% Li and 19.6% P, and then dissolved by azotic acid as Li-rich solution. When the solution was heated to 190°C for 10 h with the supplementary of saccharose, more than 99.9% Fe and 98.9% Al were removed as spherical giniite particles, in accordance with the rest of Fe/Al at the concentrations of 2.1 and 14 mg/L, whilst the loss of Li was less than 1.5%. But without saccharose, the Fe/Al removals only achieved by 99.2% and 52.1%. It is also found that the Fe/Al/Li removal achieved by 99.6%, 96% and 25.3% after adjusting the solution to pH 2.7 by NaOH. After hydrothermal treatment, the rest Li can be recycled as lithiophosphate plate by pH adjustment, in contrast to the recovery efficiency of 98.5% Li. Such method raised a facile route to effectively separate impure Fe/Al from Li-rich cathode powder, and showed promising application in the industrial recovery of spent battery.

Given the daily increase in the number of spent solar panels scrapped worldwide, these materials can be recycled as value-added heavy-metal products because of their high contents of valuable metals, such as Cu, Ag. Firstly, spent solar panels were soaked in acetone solvent and then split into three parts: glass, silicon and ethyl vinyl acetate. The wafers were dissolved in nitric acid solution to produce a leachate with 16.3, 5.9 and 1.5 g/L Cu, Al and Ag, respectively. With the addition of 35 g/L oxalate, 98.9% Cu was separated from the system in the form of high-purity moolooite, whereas the loss of Al and Ag was less than 1%. In the hydrothermal process, with the addition of 3 g glucose and 30 g/L phosphate and under the reaction condition at 190 degrees C for 10 h, 98.7% Al can be separated efficiently from the system in the form of AlPO4, and the loss of Ag was less than 0.1%. Finally, almost all of the Ag can be recovered efficiently from the system in the form of chlorargyrite through the introduction of sodium chloride. The results of the study provide a way for the effective recycling of Cu, Al and Ag in spent solar panels.

Red mud (RM) a solid waste generated by the bauxite smelting industry, is a rich source of metal resources, especially Ti, and its recycling can bring significant environmental and economic benefits. In this study, precious metal Ti was efficiently recovered from red mud using a coupled acid leaching and boiling route for the effective separation of low-value metals. The red mud which contained mainly 10.69% Si, 12.1% Al, 15.2% Ca, 10.99% Fe, and 4.37% Ti, was recovered in five steps. First, a nitric acid solution was used to leach the metals in multiple stages, resulting in an acidic leach solution with high concentrations of Fe, Al, Ti, and Ca ions 2.7 g/L, 4.7 g/L, 5.43 g/L, and 1.8 g/L, respectively. Then, a small amount of sucrose was added as a catalyst to recover Ti from the leach solution under hydrothermal conditions, resulting in the targeted recovery of 98.6% of Ti in the form of high-purity anatase while Fe, Al, and Ca remained in the solution. Next, the Fe in solution was separated as hematite products at a temperature of 110°C and a reaction time of 4 h. Similarly, the Al in the solution was separated and precipitated as boehmite by heating it at 260°C for a reaction time of 20 h. Finally, the remaining Ca in solution was recovered by simple pH regulation. Economic accounting assessment showed that the method yields $101.06 for 1 t of red mud treated, excluding labor costs. This study provides a novel approach to recover precious metals from metal wastes through the whole process resource recovery of solid waste red mud.