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Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect oxidation process, in which pollutant removal is mainly driven by the intermediate active species, especially RCS and chlorine radicals, with a strong oxidization ability produced at the anodes. In this work, we summarized the principles and pathways of the removal/degradation of pollutants (organic pollutants and ammonia nitrogen) by E-Cl and the major affecting factors including the applied current density, voltage, electrolyte concentration, initial pH value, etc. In the E-Cl system, the DSA and BDD electrodes were the most widely used electrode materials. The flow-through electrode reactor was considered to be the most promising reactor since it had a high porosity and large pore size, which could effectively improve the mass transfer efficiency and electron transfer efficiency of the reaction. Of the many detection methods for chlorine radicals and RCS, electron paramagnetic resonance (EPR) and spectrophotometry with N, N-diethyl-1,4-phenylenediamine sulfate (DPD) as the chromogenic agent were the two most widely used methods. Overall, the E-Cl process had excellent performance and prospects in treating salt-containing wastewater. [ABSTRACT FROM AUTHOR]

Advanced oxidation process (AOP) coupled with wet scrubber is an efficient and environmental technology for the treatment of volatile organic compounds (VOCs) emitted from soil thermal desorption. Developing a cost-effective, high-performing and stable catalyst for the specific scenarios is still considered a challenge. In this work, a highly active sludge-derived carbon catalyst loaded with Co 3 Fe 7 bimetallic alloy (DSHC(Fe)-Co) was elaborately designed for efficient PMS activation to achieve the deep oxidation of these toxic VOCs in AOP wet scrubber. The removal efficiency of the typical VOCs, gaseous benzene, remained above 99 % over a wide pH range from 3 to 11, which was better than that of the single Fe or Co catalyst. In addition, the system also demonstrated superior degradation performance higher than 98 % for other pollutants (toluene, xylene, ethyl acetate and cyclohexanone). A series of experiments and characterizations indicated that the free radical pathway, dominated by SO 4 •- and •OH, resulted in the outstanding removal performance of DSHC(Fe)-Co, which was attributed to the synergistic interaction between Fe and Co species. This study presents a novel method for sludge resource utilization and facilitates the application of AOP wet scrubbing technology in the treatment of VOCs. [Display omitted] • A sludge-derived carbon loaded with Co 3 Fe 7 alloy was synthesized. • Catalyst fabricated by a hydrothermal process was more stable due to lower ion leaching. • Hydroxyl radicals and sulfate radicals contributed to benzene degradation. • Bimetallic synergy between Fe and Co enhanced the activation capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel N,S co-doped carbon encapsulated Co 2 P anchored on MXene was fabricated. • The MZPC-9 catalyst exhibited excellent BPA removal (TOF/PMS = 291 L2 min−1 g−2). • The electron transfer-process (ETP) was the dominated reactive pathway. • The ETP-induced polymerization pathway of BPA was elucidated. The non-radical pathway dominated by the electron transfer process (ETP) has gained considerable attention for the removal of organic contaminants in persulfate-based advanced oxidation processes. Rationally designing new catalysts with optimized composition and structural merits and further elucidating the enhanced removal mechanism are of great importance. In this work, we successfully synthesized a nitrogen-sulfur co-doped carbon encapsulated cobalt phosphide (Co 2 P) on both sides of MXene nanosheets (MZPC) to degrade bisphenol A (BPA) from organic wastewater. The results indicated that BPA was degraded by 98.2 % in a mere 5 min using 0.1 g L-1 of peroxymonosulfate (PMS) and 0.05 g L-1 of the optimized catalyst (MZPC-9), exhibiting an excellent pseudo-first-order kinetics rate constant (k = 1.485 min−1). Uniformly dispersed Co 2 P nanoparticles (approximately 9.4 nm, calculated using the Scherrer equation) on both sides of MXene exhibited enhanced binding affinity with PMS, forming the MZPC-9-PMS* metastable complexes with potent oxidative capability. The resultant MZPC-9-PMS* complexes induced the polymerization reaction of BPA and achieved 81 % total organic carbon (TOC) removal. This study offers a novel perspective on the design of metal active centers to enhance the ETP-dominated non-radical pathway for pollutant degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The intrinsic properties of photocatalysts can be tuned by NH 2 -MIL-125 derived nitrogen-doped titania/carbon (NTC) catalysts. • Visible light-driven NTC enhanced PMS utilization efficiency for SMT degradation. • The PMS activating mechanism on NTC catalysts was elucidated. • Photo-electrons excited from NTC played the dominant role for the enhancement of PMS utilization efficiency. Enhancing the utilization efficiency of oxidant is of great importance for advanced oxidation processes (AOPs). Herein, nitrogen-doped titania dioxide/carbon (NTC7) catalyst was fabricated via pyrolyzing NH 2 -MIL-125 under nitrogen atmosphere at 700 °C. Excitation of NTC7 under visible light can successfully achieve efficient activation of peroxymonosulfate (PMS) (NTC7 + PMS + Vis). Degradation performance and PMS activation mechanism were systematically investigated using sulfamethazine (SMT) as the target pollutant. It was found that the photo-generated electrons excited from NTC7 under visible light played the dominant role in enhancing the productive consumption of PMS. Its utilization increased by 66 % (Δ[PMS]/Δ[SMT] = 7.0) in NTC7 + PMS + Vis process and the degradation rate was 2.14 times higher than that of NTC7 + PMS process. The ketonic C O groups and structural defects were responsible for the generation of 1O 2 in dark activation while radicals (•OH, O 2 •–) were more inclined to be continuously produced in NTC7 + PMS + Vis process. The involved degradation pathways, intermediates, and toxicity assessment have been studied in detail. This work provides an effective approach to enhance the utilization efficiency of oxidant for pollutant degradation by AOPs. [ABSTRACT FROM AUTHOR]

In this study, a dual-carrier catalyst is designed for efficient Fenton-like catalysis following non-radical electron-transfer process (ETP). By using 2D mesoporous carbon sandwiched MXene (MCSMx) nanosheets as dual functional substrates, Co single atoms (Co-SA) were confined within MCSMx (Co SA /MCSMx), in which the coordinated Co-N 4 sites in highly ordered mesoporous channels (∼10 nm) facilitated the adsorption of peroxymonosulfate (PMS), while the excellent conductivity of MXene as the substrate enhanced the transport of electron. The unique design of Co-SA anchored on dual carriers endows the Co SA /MCSMx with excellent PMS adsorption and rapid electron transfer, achieved nearly 100 % ETP pathway for bisphenol A (BPA) removal and highly selective degradation towards electron-rich pollutants. Moreover, the ETP-induced polymerization transfer reaction of BPA was discovered in the catalytic system, resulting in total organic carbon (TOC) removal ratios of up to 72 %. This work provides new insights into the rational design ETP-based systems for the efficient removal of organic pollutants. [Display omitted] • Co-N 4 was anchored on mesoporous carbon sandwiched MXene (MCSMx) with highly ordered mesoporous channels (∼10 nm). • The MCSMx nanosheets as bifunctional substrates, exhibits excellent pollutant enrichment and rapid electron transport. • Nearly 100 % electron transfer process (ETP) pathway for bisphenol A (BPA) removal was verified. • ETP-induced polymerization transfer reaction of BPA was discovered with TOC removal ratios of up to 72 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combining BC with Sch/Fe 3 O 4 could enhance the co-removal of CIP and ROX. • The adsorption capacity of Sch/Fe 3 O 4 /BC for multi-pollutant was obviously promoted. • Sch/Fe 3 O 4 /BC exhibited excellent reusability by heterogeneous Fenton regeneration. • Adsorption and oxidation played a synergistic role in co-removal of CIP and ROX. The widespread use of antibiotics and roxarsone (ROX) in the livestock industry poses significant challenges for their safe and efficient disposal. Schwertmannite (Sch) has been recognized as a promising environmental material for the removal of ROX due to its dual functionality in both heterogeneous Fenton reaction and arsenic adsorption. However, Sch as a typical Fe-based material generally exhibits a low adsorption capacity for antibiotics. Herein, a biochar (BC) loaded Sch-based material was developed to enhance the co-adsorption capacity for ciprofloxacin (CIP) and ROX, while enabling adsorbent regeneration via heterogeneous Fenton reaction. Under the conditions of 0.6 g/L adsorbent, 80–200 mg/L pollutants (CIP and ROX), and pH 6, the maximum adsorption capacities of Sch/Fe 3 O 4 /BC for CIP (66.9 mg/g) and ROX (220.9 mg/g) were obviously higher than that of other Fe-based adsorbents. Sch/Fe 3 O 4 /BC demonstrated regeneration efficiencies of ∼80 % for CIP and ∼60 % for ROX after seven cycles of experimentation. The adsorption mechanisms were elucidated as synergistic interactions involving pore-filling interaction, π-π electron donor–acceptor interaction, H-bonding, As-Fe coordination, and electrostatic attraction. Additionally, oxidation also contributed to the co-removal of CIP (∼27 %) and ROX (∼24 %) during the adsorption process. This study not only addresses the safe disposal of CIP and ROX but also introduces an innovative approach for the treatment of multi-pollutant contamination in water systems. [ABSTRACT FROM AUTHOR]

Dual atomic catalysts are specially designed for relay activation of peroxymonosulfate (PMS). Here, a programmable metal-triazolate framework is utilized as a precursor to introduce the bimetallic sites (containing Mn and Co) for the synthesis of contiguous Mn−N and Co−N sites anchored on nitrogen-doped porous carbon polyhedral (MCNC). Excellent decontamination performance with TOF/PMS = 46.3 L2 min−1 g−2 is observed on the MCNC, which is 1.6 and 1.5 times of single Mn and single Co catalysts. Singlet oxygen quantifying, 18O isotope labeling, and theoretical simulations jointly unravel that MCNC activates PMS through a unique "relay" mode, where one site interacts with the O atom in PMS, and the other expedites producing 1O 2 via PMS* activation. This work advances the origin activation of PMS and enhances the removal for the refractory pollutants by rational regulation of dual site synergistic catalyst, which deepens the on-demand design of Fenton-like reaction. [Display omitted] • A bimetal atomic catalyst with contiguous Mn-N and Co-N sites anchored on porous carbon polyhedral was fabricated. • Excellent BPA degradation performance with TOF/PMS = 46.3 L2 min−1 g−2 was observed. • Relay activation of PMS was elucidated via prompt adsorption and synergic stimulation. • Mn-N interacts with the O atom in PMS and the adjacent Co-N expedites producing 1O 2. [ABSTRACT FROM AUTHOR]

Integrating the merits of the substrate and active sites with the water matrix is of significant importance to design novel catalysts for peroxymonosulfate (PMS)-based advanced oxidation processes. A sandwich-like heterostructure catalyst (MCoO@Co-N-C) were fabricated via anchoring zero-dimensional metal-organic frameworks (MOFs)-derived CoO nanoparticles on two-dimensional Ti 3 C 2 T x MXene nanosheets. Benefiting from the distinctive structure, the resultant catalysts achieved excellent decontamination performance under high salinity conditions (200 mM). Nearly 100% efficiency of bisphenol A (BPA) was degraded within 10 min only using 0.05 g L−1 catalyst and 0.1 g L−1 PMS, with exceptional high turnover frequency (TOF) value (8.64 min−1) which was 22.5 times higher than that of MOFs derived catalysts without MXene. A mediated-electron transfer mechanism is found to be conducive to the oxidation of BPA. This work provides a new approach to novel catalysts designed for removing trace organic contaminants (TrOCs) in saline water. [Display omitted] • A sandwich-like heterostructure catalyst (MCoO@Co-N-C) was fabricated. • MCoO@Co-N-C essentially integrates the merits of MXene-MOFs derivatives. • Excellent decontamination performance was achieved under high salinity conditions. • A mediated-electron transfer mechanism is proposed to elucidate the degradation of BPA. [ABSTRACT FROM AUTHOR]

• BF process achieves very high removal (96%) of COD. • BF-ED process achieves very high removal (100%) of TP, TS and NH 3 -N. • Various nutrient ions can be efficiently recovered from swine wastewater. • BF-ED process realizes the resource recycling of swine wastewater. High organic matter load and nutrient concentration in swine wastewater could lead to soil and water pollution by inappropriate land irrigation. To solve the above problem, this study developed an eco-friendly bio-flocculation combined with electrodialysis (BF-ED) process, in which BF could effectively reduce the probability of ED membrane fouling and replaced subsequent biochemical treatment by ED process. High removal of TS (100 %), TP (100 %), and COD (95.68 %) from raw swine wastewater could be obtained via BF pretreatment, while high recovery efficiency of nutrient ions (98.8 % K+ and 84.3 % NH 3 -N) was achieved after ED process. Besides, dissolved organic matter was effectively removed after BF treatment, which was beneficial to reduce membrane fouling of ED reactor. Nutrient ions recovery from swine wastewater could be used as agricultural fertilizers. The proposed approach not only solve the problem of swine wastewater purification, but also realize the environmentally sustainable swine wastewater. [ABSTRACT FROM AUTHOR]