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Based on the natural air diffusion electrode (NADE) cathode, a solar-driven electrochemical integrated sewage treatment technology and equipment in a pilot scale was developed to treat dispersed rural wastewater. The non-aeration NADE had efficient and stable H 2 O 2 production performance, maintaining the H 2 O 2 output between 1474 and 1535 mg h−1 within 50 h with the current efficiency of 77.4%–80.6%. This electrochemical integrated wastewater treatment system was coupled with technologies such as dual-cathode electro-Fenton, peroxi-coagulation and photoelectro-Fenton, which effectively improved the conversion and utilization efficiency of H 2 O 2. It integrated Fenton-like oxidation, electro-oxidation and UV/H 2 O 2 , as well as Fe(OH) 3 -dominated flocculation, which could effectively remove various pollutants in wastewater. The integrated sewage treatment equipment (500 L d−1) realized the effective treatment of a rural decentralized domestic sewage, achieving simultaneous removal of chemical oxygen demand (COD), NH 3 –N, total phosphorus (TP) and bacteria. Driven by solar energy, its application feasibility, superiority and stability have been proved, providing theoretical and technical support for the efficient and low-consumption treatment of dispersed organic wastewater. [Display omitted] • Electrochemical integrated treatment equipment driven by solar energy is proposed. • The non-aeration NADE had efficient and stable H 2 O 2 production performance. • It integrates electro-oxidation, peroxi-coagulation and photoelectron-Fenton. • It has been successfully applied to the treatment of rural decentralized domestic sewage. • The pilot scale system exhibits good application feasibility, superiority and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-cathode peroxi-coagulation (PC) process and pilot device was first proposed. • It enhanced the oxidative degradation of pollutants in PC process at neutral pH. • It promoted the Fe(II) recycling cycle and greatly reduced iron sludge production. • The improved PC process could produce •OH and O 2 •- more efficiently. • Improved PC process showed application prospect in decentralized sewage treatment. An improved dual-cathode peroxi-coagulation (PC) process using natural air diffusion electrode (NADE) and HNO 3 modified carbon felt (MCF) was first proposed to improve the removal efficiency of organic pollutants in neutral and alkaline wastewater and reduce the formation of iron sludge. The improved PC process does not require any additional oxidants or catalysts, nor does it need to adjust the pH of the wastewater in advance but can directly treat actual wastewater, achieving a target pollutant (C 12 H 14 N 4 O 2 S, sulfamethazine) removal of 87%-100% within 60 min and TOC removal of 46–76% within 240 min with the corresponding energy consumption below 0.02 kWh gTOC-1. Compared with the conventional PC process, this improved process could produce hydroxyl radical (•OH) and superoxide radical (O 2 •-) more efficiently, which greatly increased the SMT removal rate constant by 3–4 times and oxidative removal proportion of organic pollutants from 42 ∼ 47% to 85 ∼ 90%. Thanks to the Fe(II) regeneration capacity of MCF to promote iron circulation, the yield of •OH was 4.1 times higher while the iron sludge production was less than a quarter when compared with that of conventional PC. The improved PC process illustrated better purification performance and lower energy consumption for actual wastewaters such as pharmaceutical wastewater, surface water and rural decentralized domestic sewage than the conventional PC process. Our work elucidated the mechanism of promoting Fe(II) regeneration through MCF cathode under alkaline conditions to enhance •OH production and O 2 •- oxidation, showing a good environmental application prospect. [ABSTRACT FROM AUTHOR]

Cost-effective pretreatment of the highly concentrated and biorefractory coking wastewater to improve biodegradability is of significant importance, while green electrochemical technologies without external chemicals addition are charming but still challenging due to its high energy consumption. In this work, a novel multi-stages flow through peroxi-coagulation (PC) was for the first time developed with graphite felt cathode modified by graphene, showing an excellent performance in removal of 71.5% COD, 72.3% phenol and 59.4% NH 3 -N and significant biodegradability enhancement with a low energy consumption as 1.2 kWh/m3. Compared with conventional flow PC, this process was more cost-effective due to more intensive . OH production and higher utilization of generated active species. Through UV spectrophotometry and GC-MS analysis, the improvement of biodegradability was attributed to the reduction of both low and high molecular weight compounds content in the coking wastewater. Comparing to the electro-Fenton, electrocoagulation and ozonation process, the proposed PC process was highly cost-effective, providing a promising and new alternative for pretreatment of coking wastewater. • A new flow through PC was first developed for coking wastewater treatment. • It showed cost-effectiveness in removal and biodegradability improvement. • The multi-stages PC advantaged over high utilization of active species and low cost. • The impact of key parameters and the fate of N in wastewater were investigated. • Improvement of biodegradability was disclosed by UV spectrophotometry and GC-MS. [ABSTRACT FROM AUTHOR]

Highlights • Simultaneous tetracycline and bacteria removal by a flow-through electro-peroxone. • This process was cost-effective for reclamation from municipal secondary effluent. • The coupling coefficient of O 3 and electrolysis was 1.2 for disinfection. • The disinfection by-products could satisfy the WHO's drinking water standard. • A possible degradation pathway of tetracycline was suggested. Abstract Pharmaceutical and personal care products as one of the micropollutants and bacteria in secondary effluent restrict the water reuse from municipal secondary effluent. Electro-peroxone (EP) process where H 2 O 2 is generated in-situ by electrolysis is an emerging advanced oxidation process and an improvement of traditional peroxone method (O 3 /H 2 O 2). In this work, a flow-through EP process was compared with ozonation and electrolysis for simultaneous disinfection and degradation of tetracycline (TC). The disinfection effect by EP was higher than the sum of standalone ozone and electrolysis and the coupling coefficient of ozonation and electrolysis in EP process was 1.2. The flow-through EP system presented similar efficiency for separately and simultaneously treating E. coli and TC. For the actual secondary effluent treatment, trihalomethanes, haloacetonitrile and halonitromethanes, the main disinfection by-products, were much lower than the WHO's thresholds for drinking water. TOC and COD removal was 44% and 65%, respectively, at flow rate of 35 mL/min. BOD 5 , bacteria, pH and other parameters in the effluent could satisfy the recreational landscape water quality standard, and the required energy consumption was 0.47 kW h/m3 at the flow rate 35 mL/min. Most of the degradation products were small-molecule organic acids, and possible degradation pathway of TC was suggested. [ABSTRACT FROM AUTHOR]

• A flow-through system based on the bifunctional cathode of Fe@BN-C/GF was developed. • The acceleration of the O 2 mass transfer promoted the stable production of 1O 2. • The SMT degradation was found not affected in the presence of inorganic salts and organic matter. • TOC removal in flow-through was 1.4 ∼ 2.4-folds that of the batch system under the pH 3 ∼ 11. • The TP, NH 3 -N and TOC in reverse osmosis concentrate could be simultaneously removed. To improve the mineralization efficiency of pollutants under wide pH ranges by self-sustained electrochemical advanced oxidation processes (EAOPs) without any reagent addition, a flow-through system based on the bifunctional cathode of B, N-doped carbon nanotubes embedded with nano-Fe0 particles that loaded on graphite felt (Fe@BN-C/GF) was developed. Dominant by 1O 2 oxidation, the sulfamethazine (SMT) degradation rate and TOC removal in this recirculated flow-through system were 2.6 ∼ 3.3-folds and 1.4 ∼ 2.4-folds that of the batch system under the pH ranges of 3 ∼ 11, respectively. The SMT degradation performance was found not affected in the presence of HCO 3 –, NO 3 –, Cl-, K+, or humic acid (HA). The Fe@BN-C/GF cathode had more potential to treat enlarged wastewater by 5-folds during 10 h operation, and the SMT and TOC removal was 99% and 70.31%, respectively. The total phosphorus (TP), ammonia nitrogen (NH 3 -N) and TOC in reverse osmosis concentrate and secondary wastewater effluent could be simultaneously removed to <0.01 mg L-1 and 8 mg L-1 by this flow-through system with a low electric energy consumption (EEC) of 0.022 and 0.18 kWh gTOC-1, respectively. This EAOPs based on the flow-through Fe@BN-C/GF cathode was self-sustained, and had very promising application prospect of high mineralization of pollutants even for low-conductivity wastewater. [ABSTRACT FROM AUTHOR]

The reduced S-modified MIL-53(Fe) was prepared by sulfurizing MIL-53(Fe) at low temperature, which was an efficient electro-Fenton catalyst at wide pH range (3–9) for sulfamethazine (SMT) degradation. The best temperature and MIL-53(Fe)/S ratio were 350 °C and 1:2, at which the BET surface area was much enlarged. The MIL-53(Fe) surface was etched by S to many 2D nanosheets with the thickness of ~50 nm, while S 2–2 replaced OH- to coordinate with Fe2+ and increased the Fe2+ content, which improved the catalytic performance. Even at initial pH of 7.0, the SMT removal was 95.8%, and the rate constant (k) in the Hetero-EF process was 16-folds of that in the Homo-EF process. The turnover frequency (TOF d) value of MIL-53(Fe)/S(1:2)−350 was 0.48 L g−1 min−1, which was 6.8 times that of commercial FeS 2. The S 2–2 in catalyst adjusted the pH superfast, and promoted the generation of Fe2+ and thus efficiently activating H 2 O 2 to form surface · OH, which was verified to be the main radical by EPR and radical scavenger experiments. This catalyst showed promising prospect for environmental application and could be regenerated by sulfidation method. S-doped MIL-53(Fe) was an excellent pH regulator, thus promoting promising application in Hetero-EF processes. [Display omitted] • S-modified MIL-53(Fe) was successfully synthesized by one-step sulfidation at low temperature. • After sulfidation, the surface of MIL-53 became rough to form 2D nanosheets, and the BET surface area was larger. • MIL-53(Fe)/S(1:2)−350 was an efficient electro-Fenton catalyst at wide pH range (3–9). • The catalytic performance of MIL-53(Fe)/S(1:2)−350 was better than that of commercial FeS 2. • For adjustment of pH by S 2–2 , O 2 played a major role first and then H 2 O 2. [ABSTRACT FROM AUTHOR]