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CoNOC with CoN (Pd)3 N (Po)1 O1 structure can efficiently catalyse the electro-Fenton reaction to generate –OH to degrade antibiotic pollutants represented by tetracyclines. [Display omitted] • Oxygen-doped Co SACs were prepared using a temperature gradient pyrolysis strategy with nitric acid oxidation method. • DFT calculations explained the excellent catalytic performance was due to the electronic modulation of Co sites by the O doping and N coordination. • TC degradation of 95 % in 120 min and mineralization efficiency of almost 90 % in 180 min were achieved in the electro-Fenton system. • The significant involvement of OH was confirmed, and the degradation pathways of TC have been analyzed and predicted. Electro-Fenton is an effective process for degrading hard-to-degrade organic pollutants, such as tetracycline (TC). However, the degradation efficiency of this process is limited by the activity and stability of the cathode catalyst. Herein, a temperature gradient pyrolysis strategy and oxidation treatment is proposed to modulate the coordination environment to prepare oxygen-doped cobalt monoatomic electrocatalysts (CoNOC). The CoNOC catalysts can achieve the selectivity of 93 % for H 2 O 2 with an electron transfer number close to 2. In the H-cell, the prepared electrocatalysts can achieve more than 100 h of H 2 O 2 production with good stability and the yield of 1.41 mol g catalyst −1 h−1 with an average Faraday efficiency (FE) of more than 88 %. The calculations indicate that the epoxy groups play a crucial role in modulating the oxygen reduction pathway. The O doping and unique N coordination of Co single-atom active sites (CoN (Pd)3 N (Po)1 O1) can effectively weaken the O 2 /OOH* interaction, thereby promoting the production of H 2 O 2. Finally, the electro-Fenton system could achieve a TC degradation rate of 94.9 % for 120 min with a mineralization efficiency of 87.8 % for 180 min, which provides a reliable option for antibiotic treatment. The significant involvement of OH in the electro-Fenton process was confirmed, and the plausible mineralization pathway for TC was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] Quinoline is high toxicity and difficult biodegradation in oil washing wastewater. Therefore, efficient removal of quinoline contaminant from water bodies poses a major challenge. Hence, Co quantum dot loaded N-doped porous carbon (CoNC) nanosheets grown in situ on carbon cloth were fabricated as cathode for the degradation of quinoline in electro-Fenton system. Under optimal conditions (c(Fe2+) = 0.5 mM, U = -0.3 V, pH = 3), quinoline was completely degraded within 15 min with superior apparent rate constant of 0.385 min−1, which was 19.6 times higher than that of the ZIF-L precursor, due to the abundance of Co QDs active sites and hydrophilicity and electrical conductivity of N-doped porous carbon. In addition, three reaction pathways for quinoline were deduced by combining Density Functional Theory (DFT) calculation and Liquid Chromatography-Mass Spectrometry (LC-MS). More importantly, in situ FTIR and free energy calculations were analyzed to reveal that pathway Ⅰ as spontaneous reaction was the main reaction pathway. Finally, the toxicity of the intermediates was assessed with ECOSAR software and E. coli experiments, and the overall toxicity decreased during the degradation reactions. This work provides novel perspectives on environmental protection by designing in-situ grown cathodes through self-assembly method, thereby effectively purifying pollutants from wastewater. [ABSTRACT FROM AUTHOR]

In this study, an Electro-Fenton process was employed to treat high-strength alcohol distillery wastewater. The simultaneously removal of chemical oxygen demand (COD), color, and turbidity were examined. The optimum value of the operational parameters including the number of electrodes and their arrangement, electrodes' interval, initial pH, and electrolyte concentration were determined by one-factor-at-a-time (OFAT). The effect of essential parameters including current density, hydrogen peroxide concentration, and the duration of the process were optimized using response surface methodology (RSM). At fixed defined operational conditions by OFAT as four electrodes in a parallel arrangement with a 1 cm interval, 0.3 mol/L of electrolyte salt, and pH of 4, respectively, the optimal condition by RSM suggested the current density of 24 mA/cm2, 40 g/L of H 2 O 2 , and reaction time of 2 h. By adopting optimal condition at defined values of operational factors the removal efficiencies for COD, color, and turbidity were approximately 83%, 99%, and 97%, respectively, using fresh water for dilution. The energy consumption of 1.9 kWh/kg COD removal was achieved. Also, to save water, the treated wastewater (instead of fresh water) was used for the dilution of the raw wastewater, indicating the satisfactory results with removal efficiencies for COD, color, and turbidity of 71%, 94%, and 95%, respectively. Overall, the Electro-Fenton process is introduced as an appropriate process for treating high-strength alcohol distillery wastewater. [Display omitted] • The Electro-Fenton process parameters were optimized by RSM. • The simultaneous removal of COD, color and turbidity was 83%, 99% and 97%, respectively. • The energy consumption of 1.9 kWh/kg COD removal was achieved by Electro-Fenton. • Treated effluent was used to dilute raw wastewater to decrease water consumption. • Using treated effluent resulted in 71% COD, 94% color, and 95% turbidity removal. [ABSTRACT FROM AUTHOR]

The performance of Electro-Fenton (EF) cathode materials is primarily assessed by H 2 O 2 yield and Fe3+ reduction efficiency. This study explores the impact of pore structure in chitin-based porous carbon on EF cathode effectiveness. We fabricated mesoporous carbon (CPC-700-2) and microporous carbon (ZPC-700-3) using template and activation methods, retaining nitrogen from the precursors. CPC-700-2, with mesopores (3–5 nm), enhanced O 2 diffusion and oxygen reduction, producing up to 778 mg/L of H 2 O 2 in 90 min. ZPC-700-3, with a specific surface area of 1059.83 m2/g, facilitated electron transport and ion diffusion, achieving a Fe2+/Fe3+ conversion rate of 79.9%. EF systems employing CPC-700-2 or ZPC-700-3 as the cathode exhibited superior degradation performance, achieving 99% degradation of Rhodamine B, efficient degradation, and noticeable decolorization. This study provides a reference for the preparation of functionalized carbon cathode materials for efficient H 2 O 2 production and effective Fe3+ reduction in EF systems. [Display omitted] • Mesoporous and microporous carbons containing nitrogen and oxygen were synthesized through pyrolysis of chitin. • Electro-Fenton cathodes were fabricated by applying the carbon materials onto graphite felt substrates. • The mesoporous carbon CPC-700-2, with an enriched pore size of 3-5 nm, demonstrates excellent H 2 O 2 production capacity. • Microporous carbon ZPC-700-3, with a specific surface area of 1059.83 m2/g, exhibits exceptional Fe3+ reduction efficiency. • Both mesoporous and microporous carbon electrodes effectively degrade RhB, with significant decolorization effects. [ABSTRACT FROM AUTHOR]

A Co 3 Mn-LDHs and carbon nanotube (Co 3 Mn-LDHs/CNT) composite catalyst was constructed for permonosulfate (PMS) activation and degrading sulfamethoxazole (SMX) under Vis light irradiation. The introduction of CNTs into Co 3 Mn-LDHs facilitate the exciton dissociation and carrier migration, and the e− and h+ were readily separated from Co 3 Mn-LDHs/CNT in the photocatalysis process, which promoted the production rate of reactive oxygen species (ROS), so the Co 3 Mn-LDHs + Vis + PMS system exhibited better activity with an SMX degradation ratio of 61.25% than those of Co 3 Mn-LDHs + Vis system (42.30%) and Co 3 Mn-LDHs + PMS system (48.30%). After 10 cycles, the degradation rate of SMX only decreased by 7.16%, indicating the good reusability of the Co 3 Mn-LDHs/CNTs catalyst. The results of electron paramagnetic resonance (EPR) analysis and radical quenching experiments demonstrated that that the SO 4 •− played crucial role for SMX removal in Co 3 Mn-LDHs/CNTs + Vis + PMS system, and both e− and h+ made an important contribution to activating PMS to produce ROS. Overall, this work provided an excellent catalyst for photo-assisted PMS activation and suggested the activation mechanism for organic pollutant remediation. [Display omitted] • Co 3 Mn-LDHs/CNT activates PMS under visible light irradiation. • Sulfate, hydroxyl and superoxide radicals are the major ROS for SMX degradation. • The e − and h + play a crucial role in activating PMS. • The Co 3 Mn-LDHs/CNT exhibits excellent activity and good reusability. [ABSTRACT FROM AUTHOR]

The persistence and stability of refractory organic compounds such as dyes in water bodies cause serious toxicity to humans. The present study provides an in-depth investigation into the evolution law of electro-Fenton (EF) oxidation to in situ electrocoagulation (EC) process and its mechanism for highly efficient removal of refractory organic pollutants. A comprehensive evaluation of the energy efficiency by EC, EF (constant pH = 3) and electrocatalytic oxidation (EO) processes under the same research levels was conducted. The results showed that in the EF-EC mode, the removal efficiency of Rhodamine B (RhB) was enhanced by 33.41% compared to the EC system. Additionally, electrode consumption is 52.9% of the EF system, and current efficiency was improved by 272.98% compared to the EO system. Hydroxyl radical (·OH) and polynuclear species (Fe(b)) are the main species to remove refractory organics and intermediates. Unlike the synergistic effect of ·OH homogeneous oxidation and electrocoagulation in the EF-EC process, the ·OH produced in the EO process mainly undergoes heterogeneous oxidation at the electrode interface. The formed iron oxides were mainly Fe 2 O 3 and ɑ-FeOOH. Density functional theory calculations and liquid chromatograph-mass spectrometer analysis indicated that the degradation of RhB mainly included deethylation, deamination, degradation, ring-opening and mineralization reactions. This study provides a valuable reference for related research in the field of environmental electrochemical remediation. [Display omitted] • Fe electrode EF-EC system could effectively remove refractory organic matter. • The evolution mechanism of EF-EC system were proposed. • EF-EC system could effectively improve the Re (RhB) and current efficiency. • ·OH and Fe(b) are the main species to remove refractory organics and intermediates. • The homogeneous and heterogeneous oxidation mechanisms of ·OH were examined. [ABSTRACT FROM AUTHOR]

Glyphosate (GLY), a globally-used organophosphate herbicide, is frequently detected in various environmental matrices, including water, prompting significant attention due to its persistence and potential ecological impacts. In light of this environmental concern, innovative remediation strategies are warranted. This study utilized Serratia sp. AC-11 isolated from a tropical peatland as a biocatalyst in a microbial fuel cell (MFC) coupled with a homogeneous electron-Fenton (EF) process to degrade glyphosate in aqueous medium. After coupling the processes with a resistance of 100 Ω, an output voltage value of 0.64 V was obtained and maintained stable throughout the experiment. A bacterial biofilm of Serratia sp. AC-11 was formed on the carbon felt electrode, confirmed by attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). In the anodic chamber, the GLY biodegradation rate was 100% after 48 h of experimentation, with aminomethylphosphonic acid (AMPA) remaining in the solution. In the cathodic chamber, the GLY degradation rate for the EF process was 69.5% after 48 h experimentation, with almost all of the AMPA degraded by the in situ generated hydroxyl radicals. In conclusion, the results demonstrated that Serratia sp. AC-11 not only catalyzed the biodegradation of glyphosate but also facilitated the generation of electrons for subsequent transfer to initiate the EF reaction to degrade glyphosate. This dual functionality emphasizes the unique capabilities of Serratia sp. AC-11, it as an electrogenic microorganism with application in innovative bioelectrochemical processes, and highlighting its role in sustainable strategies for environmental remediation. [Display omitted] • Serratia sp. AC-11, isolated from a tropical peatland, utilizes glyphosate as a carbon source for biodegradation. • Serratia sp. AC-11 is an electrogenic microorganism. • The electron transfer by Serratia sp. AC-11 activates the electron-Fenton reaction to degrade glyphosate and aminomethylphosphonic acid (AMPA). • The closed circuit enhances the rate of glyphosate biodegradation compared to the open circuit in the anodic chamber. • The coupling of the microbial fuel cell (MFC) with the electron-Fenton processeffectively eliminates glyphosate. [ABSTRACT FROM AUTHOR]

To enhance the contaminant removal efficiency of the electro-Fenton (E-Fenton) process, a nitrogen and phosphorus co-doped graphite felt (NPGF) cathode was synthesized using an anodic oxidation technique. An ascorbic acid-coupled NPGF E-Fenton system was then established for the degradation of ciprofloxacin (CIP). The NPGF cathode featured abundant oxygen-containing functional groups (such as -COOH and -OH), which enhanced the selectivity of oxygen reduction and facilitated the formation of H 2 O 2. The introduction of N and P doping disrupted the charge balance within the carbon framework, accelerating electron transfer. Together, the NPGF electrode and ascorbic acid enhanced the cycling of Fe3+/Fe2+ while preventing the formation of iron sludge. Under optimal conditions (ascorbic acid concentration of 0.3 mM, current density of 2.0 mA cm−2, pH of 3.0, aeration rate of 0.6 L min−1, and Fe2+ concentration of 0.2 mM), CIP was completely removed within 20 min. The NPGF electrode exhibited excellent stability, maintaining 95.35% CIP removal even after 8 cycles. Analysis revealed that singlet oxygen primarily mediated the degradation of CIP, with its concentration measured at 1.23 × 10−7 M. Density functional theory was used to analyze the characteristics and potential attack sites of CIP, enabling the proposal of plausible degradation pathways. Toxicity simulations and Escherichia coli growth inhibition experiments demonstrated a reduction in the toxicity of CIP and its intermediate products. This study offers a valuable reference for improving the efficiency of E-Fenton technology in antibiotic wastewater treatment. [Display omitted] • A novel N, P co-doped graphite felt (NPGF) cathode was prepared. • The NPGF cathode exhibits excellent electron transfer performance and stability. • The Fe3+/Fe2+ cycling efficiency approaches 100% in the first 5 min. • The removal of ciprofloxacin was mainly attributed to the oxidation of 1O 2 and •OH. • The degradation mechanism and pathways were revealed by experiments and DFT. [ABSTRACT FROM AUTHOR]

Tetracycline hydrochloride (TC) accumulates in large quantities in the water environment, causing a serious threat to human health and ecological environment safety. This research focused on developing cost-effective catalysts with high 2e- selectivity for electro-Fenton (EF) technology, a green pollution treatment method. Defective nitrogen-doped porous carbon (d-NPC) was prepared using the metal-organic framework as the precursor to achieve in-situ H 2 O 2 production and self-decomposition into high activity ·OH for degradation of TC combined with Co2+/Co3+. The d-NPC produced 172.1 mg L−1 H 2 O 2 within 120 min, and could degrade 96.4% of TC in EF system. The self-doped defects and graphite-nitrogen in d-NPC improved the oxygen reduction performance and increased the H 2 O 2 yield, while pyridine nitrogen could catalyze H 2 O 2 to generate ·OH. The possible pathway of TC degradation was also proposed. In this study, defective carbon materials were prepared by ball milling, which provided a new strategy for efficient in-situ H 2 O 2 production and the degradation of pollutants. [Display omitted] • Defective N-doped porous carbon was prepared by ball milling of ZIF-8 derived materials. • Intrinsic defects and nitrogen doping enhanced the oxygen reduction reaction activity. • The d-NPC has high 2e-selectivity and produced 172.1 mg L−1 H 2 O 2 within 120 min. • d-NPC exhibited excellent stability for tetracycline hydrochloride removal in electro-Fenton system. [ABSTRACT FROM AUTHOR]

The presence of levofloxacin (LEV) in aqueous solutions can pose health risks to humans, have adverse effects on aquatic organisms and ecosystems, and contribute to the development of antibiotic-resistant bacteria. This study aims to investigate the feasibility of using electrocoagulation residuals (ECRs) as a heterogeneous catalyst in the electro-Fenton process for degrading LEV. By combining electrocoagulation residuals with sodium alginate, ECRs-alginate beads were synthesized as a heterogeneous electro-Fenton composite. The response surface method was employed to investigate the optimization and influence of various operating parameters such as the initial concentration of LEV (10–50 mg/L), voltage (15–35 V), pH (3–9), and catalyst dose (1–9 g/L). The successful incorporation of iron and other metals into the ECRs-alginate beads was confirmed by characterization tests such as EDX and FTIR. By conducting a batch reaction under optimal conditions (initial LEV concentration = 20 mg/L, pH = 4.5, voltage = 30V, and catalyst dose = 7 g/L), a remarkable degradation of 99% for LEV was achieved. Additionally, under these optimal conditions, a high removal efficiency of 92.3% for total organic carbon (TOC) could be attained within 120 min and these findings are remarkable compared to previous studies. The results further indicated that the degradation of levofloxacin (LEV) could be accurately quantified by utilizing the first-order kinetic reaction with a 0.03 min−1 rate constant. The synthesized beads offered notable advantages in terms of being eco-friendly, simple to use, highly efficient, and easily recoverable from the liquid medium after use. • ECRs-alginate beads were synthesized as a heterogeneous electro-Fenton catalyst. • 99% degradation efficiency of LEV through electro-Fenton treatment was achieved. • High removal efficiency of 92.3% for TOC could be achieved within 120 min. • LEV degradation could be quantified by the first-order kinetic with a 0.03 min−1 rate constant. [ABSTRACT FROM AUTHOR]

The electro-Fenton (EF) based on gas-diffusion electrodes (GDEs) reveals promising application prospective towards recalcitrant organics degradation because such GDEs often yields superior H 2 O 2 generation efficiency and selectivity. However, the low efficiency of Fe2+/Fe3+ cycle with GDEs is always considered to be the limiting step for the EF process. In this study, activated carbon fiber (ACF) was firstly employed as co-catalyst to facilitate the performance of antibiotic cefaclor (CEC) decomposition in EF process. It was found that the addition of ACF co-catalyst achieved a rapid Fe2+/Fe3+ cycling, which significantly enhanced Fenton's reaction and hydroxyl radicals (•OH) generation. X-ray photoelectron spectroscopy (XPS) results indicated that the functional groups on ACF surface are related to the conversion of Fe3+ into Fe2+. Moreover, DMSO probing experiment confirmed the enhanced •OH production in EF + ACF system compared t o conventional EF system. When inactive BDD and Ti 4 O 7 /Ti anodes were paired to EF system, the addition of ACF could significantly improve mineralization degree. However, a large amount of toxic byproducts, including chlorate (ClO 3 −) and perchlorate (ClO 4 −), were generated in these EF processes, especially for BDD anode, due to their robust oxidation capacity. Higher mineralization efficiency and less toxic ClO 4 − generation were obtained in the EF + ACF process with Ti 4 O 7 /Ti anode. This presents a novel alternative for efficient chloride-containing organic removal during wastewater remediation. [Display omitted] • ACF exhibited excellent co-catalytic performance for Fe2+/Fe3+ circulation. • More.•OH was produced in EF + ACF system with GDE cathode to oxidize CFC. • The possible co-catalytic mechanism of ACF in EF + ACF system was proposed. • Higher mineralization and less ClO 4 − formation were achieved with Ti 4 O 7 /Ti anode. • EF + ACF showed promising application prospect for wastewater treatment. [ABSTRACT FROM AUTHOR]

Fe(II) regeneration plays a crucial role in the electro-Fenton process, significantly influencing the rate of ·OH formation. In this study, a method is proposed to improve Fe(II) regeneration through N-doping aimed at enhancing the adsorption capacity of the activated carbon cathode for Fe(III). N-doping not only enriched the pore structure on the surface of activated carbon, providing numerous adsorption sites, but also significantly increased the adsorption energy for Fe(III). Among the types of nitrogen introduced, pyridine-N exhibited the most substantial enhancement effect, followed by pyrrole-N, while graphite-N showed a certain degree of inhibition. Furthermore, N-doping facilitated the adsorption of all forms of Fe(III) by activated carbon. The adsorption and electrosorption rates of the NAC-900 electrode for Fe(III) were 30.33% and 42.36%, respectively. Such modification markedly enhanced the Fe3+/Fe2+ cycle within the electro-Fenton system. The NAC-900 system demonstrated an impressive phenol degradation efficiency of 93.67%, alongside the lowest electricity consumption attributed to the effective "adsorption-reduction" synergy for Fe(III) on the NAC-900 electrode. Compared to the AC cathode electro-Fenton system, the degradation efficiency of the NAC-900 cathode electro-Fenton system at pH = levels ranging from 3 to 5 exceeded 90%; thus, extending the pH applicability of the electro-Fenton process. The degradation efficiency of phenol using the NAC-900 cathode electro-Fenton system in various water matrices approached 90%, indicating robust performance in real wastewater treatment scenarios. This research elucidates the impact of cathodic Fe(III) adsorption on Fe(II) regeneration within the electro-Fenton system, and clarifies the influence of different N- doping types on the cathodic adsorption of Fe(III). [Display omitted] • Nitrogen atom enhanced the adsorption of Fe(III) on activated carbon. • Pyridine-N and pyrrole-N promoted adsorption, while graphite-N inhibited adsorption. • N-doping promoted the adsorption of all forms of Fe(III). • N-doping modification significantly promoted the Fe3+/Fe2+ cycle. • N-doping effectively broadened the pH application range of electro-Fenton. [ABSTRACT FROM AUTHOR]

The present work demonstrates a novel strategy of synthesizing iron-biochar (Fe@BC SB) composite made with the waste iron bottle cap and sugar cane bagasse for implementation in the three-dimensional electro-Fenton (3DEF) process. The catalytic ability of the Fe@BC SB composite was explored to remediate the sodium dodecyl sulphate (SDS) surfactant from wastewater at neutral pH. At the optimum operating condition of Fe@BC SB dose of 1.0 g L−1, current density of 4.66 mA cm−2, and Na 2 SO 4 dose of 50 mM, nearly 92.7 ± 3.1% of 20 mg L−1 of SDS abatement was attained during 120 min of electrolysis time. Moreover, the Fe@BC SB showed significant recyclability up to six cycles. Besides, other organics were successfully treated with more than 85% abatement efficiency in the proposed Fe@BC SB -supported 3DEF process. The total operating cost obtained during SDS treatment was around 0.31 US$ m−3 of wastewater. The phytotoxicity test revealed the positive impact of the 3DEF−treated effluent on the germination of the Vigna radiata. The electron paramagnetic resonance conveyed •OH as the prevailing reactive species for the oxidation of SDS in the 3DEF process. Further, about 81.3 ± 3.8% of SDS and 53.7 ± 4.1% of mineralization efficacy were acquired from the real institutional sewage. [Display omitted] • A novel waste-derived iron-biochar catalyst (Fe@BC SB) was synthesized. • The Fe@BC SB showed successful efficacy in three-dimensional electro-Fenton (3DEF). • The Fe@BC SB revealed high stability, reusability and H 2 O 2 production. • More than 90% of surfactant removal was achieved using 3DEF process. • The hydroxyl radical was the dominant species for mineralization of surfactant. [ABSTRACT FROM AUTHOR]

Although the electro-Fenton (EF) process is effective for wastewater treatment, recycling spent catalysts remain a major challenge. Therefore, we introduce a reuse strategy for spent catalysts where an iron hydroxyphosphate [Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O] catalyst is utilized. Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O obtained •OH and •O 2 − by activating in-situ produced H 2 O 2 , and the degradation rate of sulfamethoxazole reached 94.5% after 120 min and showed excellent stability (maintained above 90%) for 10 cycles. Finally, the used catalyst was converted into slow-release ammonium ferrous phosphate (NH 4 FePO 4 ·H 2 O) fertiliser at a conversion rate of 85.6%. NH 4 FePO 4 ·H 2 O significantly promoted plant and seed growth within 6 days, highlighting the contribution of the resource recycling of the spent catalyst. This study serves as a valuable reference for the efficient utilization of spent catalysts. This study successfully applied EF catalysts and explored the recycling of spent catalysts. • The investigation of electro-catalyst recovery and the utilization of EF process have been conducted. • The catalyst Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O showed good degradation performance of the recalcitrant pollutant sulfamethoxazole. • The catalyst promoted the production of.•OH and •O 2 − during the EF process. • The catalyst was converted into a slow-release fertilizer NH 4 FePO 4 for plant growth. [ABSTRACT FROM AUTHOR]

This study investigated the removal performance of ofloxacin (OFL) by a novel electro-Fenton enhanced microfiltration membrane. The membranes used in this study consisted of metal-organic framework derived porous carbon, carbon nanotubes and Fe2+, which were able to produce hydroxyl radicals (•OH) in-situ via reducing O 2 to hydrogen peroxide. Herein, membrane filtration with bias not only concentrated the pollutants to the level that could be efficiently treated by electro-Fenton but also confined/retained the toxic intermediates within the membrane to ensure a prolonged contact time with the oxidants. After validated by experiments, the applied bias of −1.0 V, pH of 3 and electrolyte concentration of 0.1 M were the relatively optimum conditions for OFL degradation. Under these conditions, the average OFL removal rate could be reach 75% with merely 5% membrane flux loss after 4 cycles operation by filtrating 1 mg/L OFL. Via decarboxylation reaction, piperazinyl ring opening, dealkylation and ipso substitution reaction, etc., OFL could be gradually and efficiently degraded to intermediate products and even to CO 2 by •OH. Moreover, the oxidation reaction was preferred to following first-order reaction kinetics. This research verified a possibility for antibiotic removal by electro-enhanced microfiltration membrane. [Display omitted] • Electro-Fenton combined with membrane filtration is used to antibiotics degradation. • Ofloxacin degradation rate can reach 78.7% by electro-Fenton filtration. • Membrane permeate flux could recover to 95.2% in 5 cycles by hydraulic cleaning. [ABSTRACT FROM AUTHOR]

• A dual electrochemical catalysis toward oxygen reduction to H 2 O 2 at Bi 2 Mo 3 O 12 cathode was proposed. • Bi 2 Mo 3 O 12 with oxygen vacancies directly catalyzes H 2 O 2 production. • Electro-reduced Bi species are involved to catalyze H 2 O 2 production. • H 2 O 2 yield remained unchanged in the wide pH range of 3.0–9.0. • EF system with Bi 2 Mo 3 O 12 /Ti cathode showed high efficiency for AOII degradation. In electro-Fenton (EF) technique, the yield of H 2 O 2 is one of important factors affecting the wastewater treatment efficiency, which greatly depends on the cathode material. Recently the metal oxide modified cathode has become one of the most efficient materials for oxygen reduction and H 2 O 2 production. In this paper, a bismuth molybdate with distorted scheelite structure, Bi 2 Mo 3 O 12 , was synthesized and used as cathode to catalyze H 2 O 2 production. The prepared Bi 2 Mo 3 O 12 was characterized by SEM, FTIR and XPS. The study on voltammetric behavior of Bi 2 (MoO 4) 3 /Ti cathode found that Bi 2 Mo 3 O 12 had a dual electrochemical catalysis for H 2 O 2 production, and that was further verified by the high yield of H 2 O 2 for short time in bulk electrolysis. The dual electrochemical catalysis includes a direct electrochemical catalysis and an indirect Bi0 mediated chemical catalysis. Production of chemisorbed oxygen, which is caused by the oxygen vacancies originated from both the distorted scheelite lattice and the electro-generated lower-valence Bi specie at lattice surface, contributes to the direct catalysis. Otherwise, the electro-generated Bi0 from Bi3+ reduction reacts with adsorbed oxygen to H 2 O 2 , enhancing H 2 O 2 production. Additionally, Bi 2 Mo 3 O 12 /Ti was used as cathode in EF system containing ferric alginate gel beads. This EF system shows high efficient characteristics toward the degradation of acid orange II (AOII), and the removal percentage of AOII maintained about 94% in the wide pH range of 3.0–9.0. In brief, this paper not only provides a high efficient Bi 2 (MoO 4) 3 /Ti cathode for H 2 O 2 production, but also reveals a dual catalysis mechanism using Bi 2 (MoO 4) 3 modified cathode in EF system. [ABSTRACT FROM AUTHOR]

Abstract The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H 2 O 2 (AO-H 2 O 2), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO 2 -based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO 2 -based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe2+ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm−2 yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids. Highlights • Degradation of bentazon by OH, M(OH) and sunlight in solar photoelectro-Fenton (SPEF). • SPEF outperformed AO-H 2 O 2 , EF and PEF, whereas BDD was better than Pt and Ti.|RuO 2 • Total herbicide removal by SPEF with BDD anode in 20 min at j = 16.6 mA cm−2 in Na 2 SO 4. • Total but slower removal in urban wastewater after 45 min due to NOM interference. • Reaction pathway: 7 non-chlorinated aromatics, 16 chloro-aromatics and 2 chloro-aliphatics. [ABSTRACT FROM AUTHOR]

Heterogeneous electro-Fenton (EF) process is emerging as an attractive treatment technology for removal of sulfadiazine (SDZ), in which in situ generation of H 2 O 2 and Fe(II) are crucial steps. In this study, Pt-FeO X /G was synthesized as a heterogeneous EF catalyst by incorporating Pt single atoms into a FeO X nanocrystal. The optimized Pt 1 -FeO X /G cathode exhibited an SDZ conversion of >90% within 30 min over a broad pH range (3–11). The Pt 1 -FeO X /G cathode under a strong alkaline medium exhibited very prominent selectivity to H 2 O 2 via 2e− oxygen reduction reaction with a maximum H 2 O 2 concentration of 211.93 mg L−1. The hydroxyl radicals in the cathodic chamber were mainly derived from the in situ conversion of generated H 2 O 2 in the heterogeneous EF system. The structure-activity results of Pt-FeO X /G suggested that the SDZ removal efficiency was closely related to the decentralized morphology and electronic configuration of the Pt-FeO X microcrystalline structure. Three possible SDZ degradation pathways, dominated by S–N bond cleavage, were proposed based on the stage products. The toxicity of the major products was determined using the ecological structure-activity relationship model in conjunction with trophic aquatic organisms. This study demonstrated the feasibility of enhancing heterogeneous EF catalysis for antibiotic-polluted water using multifunctional single-atom alloy cathodes. [Display omitted] • Pd-FeO X /G as heterogeneous EF cathodes could broaden the applicable pH range. • Pd-FeO X /G cathodes has the capacity for in-situ H 2 O 2 production and Fe(II) regeneration. • The introduction of Pt atoms into FeO X crystals improves the removal efficiency of SDZ. • The heterogeneous EF system could effectively reduces toxicity of SDZ-polluted water. [ABSTRACT FROM AUTHOR]

A comparative degradation of antibiotic cefaclor (CEC) between Ti/Ti 4 O 7 and Ti/RuO 2 anodes, in terms of degradation kinetics, mineralization efficiency, and formation of toxic chlorate (ClO 3 −) and perchlorate (ClO 4 −), was performed with electrochemical-oxidation (EO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes. Besides, CEC degradation by EF with boron-doped diamond (BDD) anode was also tested. Results showed CEC decays always followed pseudo-first-order kinetics, with increasing apparent rate constants in the sequence of EO < EF < PEF. The mineralization efficiency of the processes with Ti/Ti 4 O 7 anode was higher than that of Ti/RuO 2 anode, but slightly lower than that of BDD anode. Under the optimal conditions, 94.8% mineralization was obtained in Ti/Ti 4 O 7 -PEF, which was much higher than 64.4% in Ti/RuO 2 -PEF. The use of Ti/RuO 2 gave no generation of ClO 3 − or ClO 4 −, while the use of Ti/Ti 4 O 7 yielded a small amount of ClO 3 − and trace amounts of ClO 4 −. Conversely, the use of BDD led to the highest generation of ClO 3 − and ClO 4 −. The reaction mechanism was studied systematically by detecting the generated H 2 O 2 and •OH. The initial N of CEC was released as NH 4 + and, in smaller proportion, as NO 3 −. Four short-chain carboxylic acids and nine aromatic intermediates were also detected, a possible reaction sequence for CEC mineralization was finally proposed. • Influence of anode materials on cefaclor (CEC) mineralization was investigated. • Higher mineralization and fewer perchlorate were achieved with Ti/Ti 4 O 7 anode. • A plausible CEC mineralization pathway involving •OH by EF and PEF was proposed. • Ti/Ti 4 O 7 was suitable for EF and PEF treatment of chlorinated organic wastewater. • The comparation of toxic by-products generation for different anodes. [ABSTRACT FROM AUTHOR]

Abstract The present work undertakes an examination and comparison of electro-Fenton (EF), electro-peroxi-coagulation (EPC) and electrocoagulation (EC) applied to the E. coli inactivation in batch reactor. Indeed, platinum (Pt (anode), EF), stainless steel (SS (cathode), EF, EPC) and ordinary steel (Fe (anode), EPC) and aluminum (Al, EC) were used respectively. The current intensity, nature of electrolytic support, bacterial density and hydrogen peroxide (H 2 O 2) concentration are the most influenced study parameters. The obtained results showed that the high current intensities were significant for better inactivation and destruction of E. coli cells and caused a maximum of energy consumption. Both disinfection and energy consumption were improved by adding NaCl (or Na 2 SO 4) in the three processes. Higher cellular density limited the electrochemical process and has negative effect in E. coli inactivation and the energy consumption. Only in the EPC case, the disinfection was considerably increased in function with H 2 O 2 concentration. The modeling parameters of the inactivation kinetics of E. coli showed a good fitting of the established model (0.9560 < R2 < 0.9979, 0.9267 < R2 adjusted <0.997 and 0.0189 < RMSE <0.4821), faster kinetics of E. coli inactivation (significant values of K max and Sl) in the case of high current intensity (0.2442< K max <0.7440 and 10.50 < Sl < 24.69) , the presence of chlorides or sulfates (0.6662< K max <0.7818 and 11.67 < Sl < 18.59), and the sufficient H 2 O 2 concentration (0.4712< K max <0.9204 and 13.00 < Sl < 16.38). Moreover, the analysis of the results revealed that the EF is more effective in terms of the E. coli inactivation and the energy consumption comparatively to the other studied processes. Graphical abstract Image 1 Highlights • E.coli inactivation is more important with Electro-Fenton and Electro-Peroxi-coagulation. • Electrolysis with chloride ions showed significant improvement on E. coli inactivation. • The kinetic of E. coli inactivation was successfully fitted by the suitable modeling. • Electro-Fenton and Electro-peroxi-coagulation use the minimum of electric energy. [ABSTRACT FROM AUTHOR]

Phosphorus is an essential and irreplaceable element of the ecosystem. In this work, phosphorus has been recovered using an electro-Fenton process. The effects of current intensity, initial pH and H 2 O 2 concentration on the recovery of hypophosphite were investigated. When the current intensity, pH value, and H 2 O 2 concentration were 0.2 A, 3.0 and 90 mM, respectively, hypophosphite was completely oxidized to phosphate. Under such conditions, the phosphate was recovered through the generation of deposition. In order to determine the mechanism of hypophosphite recovery, the morphology and microstructure of the deposition were analyzed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, high resolution transmission electron microscopy, Fourier transform infrared and X-ray photoelectron spectra. The generation of hydroxyl radicals was confirmed using electron spin resonance technique. This method is a clean process for phosphorus recovery, and does not generate hazardous substances. [ABSTRACT FROM AUTHOR]

Due to the high dependence on the pH of influent water and the level of ferrous species, the applicability of the electro-Fenton (EF) system is poor. A highly applicable dual-cathode (DC) EF system with self-adjusting pH and ferrous species is proposed: gas diffusion electrode (GDE) for generation H 2 O 2 and Fe/S doped multi-walled carbon nanotubes (Fe/S-MWCNT) modification active cathode (AC) for adjusting pH and iron species. The strong synergistic enhancement effect between two cathodes (synergy factor up to 90.3%) improves the catalytic activity of this composite system about 12.4 times higher than that of cathode alone. Impressively, AC has the ability of self-regulate to shift towards the optimal Fenton pH (around 3.0) without adding reagents. Even pH can be adjusted from 9.0 to 3.4 within 60 min. This characteristic gives the system a wide range of pH applications, while avoiding the disadvantage of the high cost of traditional EF in pre-acidification. Furthermore, DC has a high and stable ferrous species supply, and the iron leaching amount is about twice less than that of heterogeneous EF system. Long-term stability of the DC system and its easy activity regeneration exhibit the potential of environmental remediation in industrial application. • A dual-cathode electro-Fenton system with high availability was proposed. • The system was capable of self supplying Fe2+ and automatically optimizing pH. • Strong synergetic mechanism of two cathodes ensured the full production of.•OH. • Rapid activation of H 2 O 2 along with lower iron leaching was obtained. • The system exhibited wide pH application range and long-term stability. [ABSTRACT FROM AUTHOR]

Natural Martite ore particles and graphite were modified by alternating current (AC) glow discharge plasma to form nanostructured catalyst and cathode electrode for using in the heterogeneous-electro Fenton-like (Het-EF-like) process. The performance of the plasma-treated martite (PTM) and graphite electrode (PTGE) was studied for the treatment of paraquat herbicide in a batch system. 85.78% degradation efficiency for 20 mg L −1 paraquat was achieved in the modified process under desired operational conditions (i.e. current intensity of 300 mA, catalyst amount of 1 g L −1 , pH = 6, and background electrolyte (Na 2 SO 4 ) concentration of 0.05 mol L −1 ) which was higher than the 41.03% for the unmodified one after 150 min of treatment. The ecofriendly modification of the martite particles and the graphite electrode, no chemical needed, low leached iron and milder operational pH were the main privileges of plasma utilization. Moreover, the degradation efficiency through the process was not declined after five repeated cycles at the optimized conditions, which proved the stability of the nanostructured PTM and PTGE in the long-term usage. The archived results exhibit this method is the first example of high efficient, cost-effective, and environment-friendly method for generation of nanostructured samples. [ABSTRACT FROM AUTHOR]

The widespread presence of humic acids (HAs) and chromium (Cr) in aquatic systems and drinking water sources is a serious threat to the environment and human being. However, no studies on the potential interaction and simultaneous removal of these two types of contaminants have been conducted. Here, a novel electro-Fenton process was reported for the effective and simultaneous removal of HAs and Cr(VI), where H 2 O 2 was in situ produced from the electro-generated H 2 and O 2 on the Pd/Fe 3 O 4 nanocatalyst surface and Fe(II) was provided from the support. We show that HAs exhibit as reductants and sorbents as well as electron shuttles for the removal of Cr(VI); HAs were efficiently mineralized, as revealed by a total organic carbon removal efficiency of beyond 90%, and Cr(VI) was completely reduced with 90% of total Cr removal. The Pd/Fe 3 O 4 nanocatalysts, as electron transfer and hydrogen atom transfer carriers, were found to play fundamental roles for the removal of HAs and Cr(VI). The HAs degradation was driven by the sequentially involved O 2 - and OH radicals during electro-Fenton process. The reduction of Cr(VI) was primarily attributed to the contributions from Pd/Fe 3 O 4 nanoparticles and atomic hydrogen on the catalyst surface. In a similar manner, a good recycle of Fe 3+ to Fe 2+ was accelerated, which favored the Fenton reaction to generate reactive oxidizing species. Importantly, the energy consumption of this electro-Fenton process for HAs degradation was almost 2 orders of magnitude lower than those of reported electrochemical oxidation. The Pd/Fe 3 O 4 nanocatalysts showed excellent removal performances for HAs and Cr(VI) after eight times repeated treatment. This work reports a cost-effective methodology for simultaneous removal of HAs and Cr(VI) and provides a new insight into efficient elimination of complex contaminants by heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

This study presents a systematic study on sequential treatment of highly resistant landfill leachate by electrocoagulation (EC)/aeration, sulfate radical advanced oxidation process (SR-AOP) and electro-Fenton (EF). In case of SR-AOP, peroxymonosulfate (PMS) catalyzed by zero valent iron (ZVI) and ultraviolet irradiation (UV) system was developed. Treatment process was optimized in respect to COD removal. Analysis of results revealed that sequential application of EC/aeration, PMS/ZVI/UV, and EF processes provide an extraordinary performance and meet the environmental regulations. The source of iron for EF process was provided from previous process reducing the cost of sequential process. Separately, EC/aeration (inlet COD = 4040 mg/L), PMS/ZVI/UV (inlet COD = 1560 mg/L), and EF (inlet COD = 471 mg/L) removed 61, 69 and 82% of COD respectively. Overall, sequential processes of EC/aeration, PMS/ZVI/UV and EF could remove the COD, TOC and ammonia of the landfill leachate around 98%, 93% and 94%, respectively. The comparison of different sequences of following processes indicated that current configuration (EC/aeration-PMS/ZVI/UV-EF) could meet the discharge standards. Furthermore, humification degree was significantly improved after oxidative processes. Biodegradability study was also performed by means of BOD/COD, average oxidation state (AOS), and Zahn-Wellens test, and the best results associated with these indices were obtained 0.56, 2.37, and over 98%, respectively. Phytotoxicity of leachate was remarkably reduced and the final effluent can be considered as a non-phytotoxic wastewater. [Display omitted] • EC/aeration, PMS/ZVI/UV and EF process were sequentially used for landfill leachate treatment. • More than 95% of COD, TOC and ammonia was reduced during sequential treatment. • EF used residual ferrous from ZVI for enhanced removal of COD. • Biodegradability was dramatically improved during sequential treatment. • Phytotoxicity of the final effluent was significantly reduced. [ABSTRACT FROM AUTHOR]

Fe-doped carbon xerogels with a highly developed graphitic structure were synthesized by a one-step sol-gel polymerization. These highly graphitic Fe-doped carbons are presented as promising dual-functional electro-Fenton catalysts to perform both the electro-reduction of O 2 to H 2 O 2 and H 2 O 2 catalytic decomposition (Fenton) for wastewater decontamination. The amount of Fe is key to the development of this electrode material, since affects the textural properties; catalyzes the development of graphitic clusters improving the electrode conductivity; and influences the O 2 -catalyst interaction controlling the H 2 O 2 selectivity but, at the same time is the catalyst for the decomposition of the electrogenerated H 2 O 2 to OH• radicals for the organic pollutants oxidation. All materials achieve the development of ORR via the 2-electron route. The presence of Fe considerably improves the electro-catalytic activity. However, a mechanism change seems to occur at around −0.5 V in highly Fe-doped samples. At potential lower than −0.5 eV, the present of Feδ+ species or even Fe–O–C active sites favour the selectivity to 2e-pathway, however at higher potentials, Feδ+ species are reduced favoring a O–O strong interaction enhancing the 4e-pathway. The Electro-Fenton degradation of tetracycline was analyzed. The TTC degradation is almost complete (95.13%) after 7 h of reaction without using any external Fenton-catalysts. [Display omitted] • Fe-doped carbon gels with a highly developed graphitic structure were synthesized. • The presence of Fe considerably improves the electro-catalytic activity. • The present of Feδ+ or Fe–O–C active sites favour the selectivity to 2e-pathway. • Almost total TTC degradation (95.13%) is achieved after 7 h of reaction. • Fe-doped carbon are excellent dual-functional catalysts for water decontamination. Synopsis:Fe-doped carbon xerogels with a highly developed graphitic structure were synthesized and evaluated as promising dual-functional electrodes for wastewater decontamination. [ABSTRACT FROM AUTHOR]

The efficient catalytic activity and strong durability possibility of carbon-based three-dimensional fiber materials remains an important challenge in Electro-Fenton advanced oxidation technology. Graphite felt (GF) is a promising electrode material for 2-electron oxygen reduction reaction but with higher catalytic inertia. Anodizing modification of GF has been proved to enhance it electro-catalytic property, but the disadvantages of excessive or insufficient oxidation of GF need further improved. Herein, the surface reconstituted graphite felt by anodizing and HNO 3 ultrasonic integrated treatment was used as cathode to degrade norfloxacin (NOR) and the substantial role of different modification processes was essentially investigated. Compared with the single modification process, the synergistic interaction between these two methods can generate more defective active sites (DASs) on GF surface and greatly improved 2-electron ORR activity. The H 2 O 2 can be further co-activated by Fe2+ and DASs into •OH (ads and free) and •O 2 − to efficiently degrade NOR. The treated GF with 20 min anodizing and 1 h HNO 3 ultrasound had the highest electrocatalytic activity in a wide electric potential (−0.4 V to −0.8 V) and pH range (3–9) in system and the efficient removal rate of NOR was basically maintained after 5 cycles. Under optimal reaction conditions, 50 mg L−1 NOR achieved 93% degradation and almost 63% of NOR was completely mineralized within 120 min. The possible NOR degradation pathways and ecotoxicity of intermediates were analyzed by LC-MS and T.E.S.T. theoretical calculation. This paper provided the underlying insights into designing a high-efficiency carbon-based cathode materials for commercial antibiotic wastewater treatment. Mechanism of Electro-Fenton removal NOR by surface co-activation reconstruction graphite felt cathode. [Display omitted] • The edge and isomerism DASs were introduced on GF surface. • The co-activated GF enhanced NOR degradation with excellent reusability. • The EH-GF electrode had a wide electric potential and pH range for NOR removal. • The Fe2+ and DASs cooperatively transform H 2 O 2 into.•OH. • The removal mechanism, pathways, and ecotoxicity of NOR were analyzed. [ABSTRACT FROM AUTHOR]

Conventional sanitary landfill leachate treatment has recently been complemented and, in some cases, completely replaced by reverse osmosis technology. Despite the good quality of treated water, the efficiency of the process is low and a large volume of reverse osmosis concentrate has to be either discharged or further treated. In this study, the use of anodic oxidation combined with electro-Fenton processes to treat the concentrate obtained in the reverse osmosis of sanitary landfill leachate was evaluated. The anodic oxidation pretreatment was performed in a pilot plant using an electrochemical cell with boron-doped diamond electrodes. In the electro-Fenton experiments, a boron-doped diamond anode and carbon-felt cathode were used, and the influence of the initial pH and iron concentration were studied. For the experimental conditions, the electro-Fenton assays performed at an initial pH of 3 had higher organic load removal levels, whereas the best nitrogen removal was attained when the electrochemical process was performed at the natural pH of 8.8. The increase in the iron concentration had an adverse impact on treatment under natural pH conditions, but it enhanced the nitrogen removal in the electro-Fenton assays performed at an initial pH of 3. The combined anodic oxidation and electro-Fenton process is useful for treating the reverse osmosis concentrate because it is effective at removing the organic load and nitrogen-containing species. Additionally, this process potentiates the increase in the biodegradability index of the treated effluent. [ABSTRACT FROM AUTHOR]

Microbial fuel cell-electro-Fenton system (MEF) has attracted attention due to refractory organic pollutants removal, where H 2 O 2 is in-situ produced without external energy supply. Enhancement of H 2 O 2 production and the activation of H 2 O 2 to ·OH are the keys to improve degradation performance. Development of bifunctional catalytic cathode is a viable strategy. Herein, the α-FeOOH/MoS 2 nanocomposites was fabricated by a novel facile hydrothermal method based on molybdenite-exfoliated MoS 2 nanosheets suspension, which was used as modified cathode in a MEF system. The obtained α-FeOOH/1 wt%MoS 2 cathode exhibited highest power density of 292.38 mW/m2, which was about 3.7 and 1.7 times higher than that of graphite plate and α-FeOOH, respectively. Doping of MoS 2 nanosheets significantly enhanced electrocatalytic activity of the cathode and promoted in-situ H 2 O 2 generation. Meanwhile, the exposed reductive Mo4+ on the surface of MoS 2 could greatly facilitate the conversion cycle of Fe(III)/Fe(II), leading to the efficient activation of H 2 O 2 into ·OH. The MEF with α-FeOOH/1 wt%MoS 2 cathode exhibited excellent degradation and mineralization performance for MB, rhodamine B and tetracycline hydrochloride at optimized reaction condition. Furthermore, the MEF can simultaneously achieve MB oxidation and Cr(VI) reduction, and the corresponding removal ratio can reach up to 91.45% and 100%, respectively. Based on simple preparation method as well as recyclability and excellent catalytic property, the α-FeOOH/MoS 2 composite catalyst is considered as a promising MEF cathode for efficient wastewater treatment. • MoS 2 nanosheets exfoliated from molybdenite were inserted into α-FeOOH nanorod. • A MFC-electro-Fenton system was built with α-FeOOH/1 wt%MoS 2 cathode. • The composite cathode exhibited stable and excellent bifunctional catalytic activity. • The MFC-electro-Fenton presented excellent potential for wastewater treatment. [ABSTRACT FROM AUTHOR]

In this study, a microbial fuel cell powered electro-Fenton system (MFCⓅEFs) was established in order to overcome the shortcomings of low electron flux and unexpected methane production, while simultaneously treating excess sludge (ES, substrate) and refractory syringic acid (SA). A strategy of co-adding lysozyme (LZ, as ES degradation catalyst) and 2-bromoethanesulfonate (BES, as methane inhibitor) into ES was optimized in MFCⓅEFs to maximize electron flux, microbial community diversity and functional gene abundance. The removal of sludge total chemical oxygen demand (TCOD) achieved 81.69% in 25 d under an optimal co-addition strategy (40.41 mg/gSS of LZ, 27.03 mmol/L of BES, adding on 22.8 h of the7th day), with a simultaneous high degradation of SA (99.30% in 25 h). Correspondingly, a maximum power density of 3.35 W/m3 was achieved (only 0.62 W/m3 from the control), which effectively realizes in-situ micro-electricity generation and utilization for bioelectric Fenton processes. Moreover, 42.25% of the total charges were employed for bio-electricity generation. The electricigens of Pseudomonas, Acinetobacter and Chlorobium showed effective enrichment, while the abundance of methanogenesis archaea was extremely decreased. Functional genes associated with methanogenesis including mtaA, hdra, and mcrA were effectively inhibited. The life cycle assessment along with an optimized co-addition strategy illustrated a beneficial environmental effect, particularly in terms of ecosystem quality and climate change. Above all, an enhanced synchronous degradation of excess sludge and refractory pollutants had been realized in a green and environmentally friendly way. [Display omitted] • Co-adding lysozyme and 2-bromoethanesulfonate was optimized by CCD calculation. • The removals of sludge TCOD and SA reached 81.69% and 99.30%, respectively. • Optimal co-addition strategy promoted active bio-electron ratio of electron fluxes. • Exoelectrogens were effectively enriched and methanogensis was inhibited. • The damage categories of climate change were greatly decreased in optimal MFCⓅEFs. [ABSTRACT FROM AUTHOR]

Nowadays, the removal of pharmaceutical contaminants from water resources and wastewater is of great importance due to environmental and health issues. Over the decades, various methods have been reported to remove pollutants from wastewater. Among the developed methods, advanced oxidation processes (AOPs) have received significant attention from researchers. In this study, we report the one-pot synthesis of graphene hydrogel-metal (GH-M, M: Co, Ni, Cu) nanocomposites via the combination of polyol and hydrothermal methods. The structure of the resulting nanocomposites was examined by transmission electron microscopy (TEM), inductively coupled plasma-mass spectroscopy (ICP-MS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy methods. Afterward, as-prepared GH-Cu, GH-Co, and GH-Ni nanocomposites were used to prepare cathodes for the electro-Fenton (EF) process to remove rifampicin (RIF) from polluted water. The effect of operational parameters, including current density (mA/cm2), initial pH, initial RIF concentration (mg/L), and process time (min) was investigated via response surface methodology (RSM). The optimal values for current density, pH, initial RIF concentration, and process time using GH-Ni as cathode were 30 mA/cm2, 5, 30 mg/L, and 90 min, respectively. The results at optimal values showed that the maximum RIF removal efficiency for GH-Cu, GH-Co, and GH-Ni cathodes was 90.47, 92.60, and 93.69%, respectively. Brunauer Emmett Teller (BET), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and cyclic voltammetry (CV) analyses were performed to investigate the performance of the cathodes for the RIF removal. Finally, total organic carbon (TOC), gas chromatography–mass spectrometry (GC-MS), and atomic absorption spectroscopy (AAS) analyses were performed for further investigation of the RIF removal from polluted water. The results claimed that one-pot synthesized GH-M cathodes can effectively remove RIF from polluted water through EF process. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency of soil washing treatment of hydrocarbon contaminated soils, an innovative combination of this soil treatment technique with an electrochemical advanced oxidation process (i.e. electro-Fenton (EF)) has been proposed. An ex situ soil column washing experiment was performed on a genuinely diesel-contaminated soil. The washing solution was enriched with surfactant Tween ® 80 at different concentrations, higher than the critical micellar concentration (CMC). The impact of soil washing was evaluated on the hydrocarbons concentration in the leachates collected at the bottom of the soil columns. These eluates were then studied for their degradation potential by EF treatment. Results showed that a concentration of 5% of Tween ® 80 was required to enhance hydrocarbons extraction from the soil. Even with this Tween ® 80 concentration, the efficiency of the treatment remained very low (only 1% after 24 h of washing). Electrochemical treatments performed thereafter with EF on the collected eluates revealed that the quasi-complete mineralization (>99.5%) of the hydrocarbons was achieved within 32 h according to a linear kinetic trend. Toxicity was higher than in the initial solution and reached 95% of inhibition of Vibrio fischeri bacteria measured by Microtox ® method, demonstrating the presence of remaining toxic compounds even after the complete degradation. Finally, the biodegradability (BOD 5 /COD ratio) reached a maximum of 20% after 20 h of EF treatment, which is not enough to implement a combined treatment with a biological treatment process. [ABSTRACT FROM AUTHOR]

Worldwide, most solid waste ends its life in landfill sites, which have a significant environmental impact in several respects. In particular, rainfall over landfill sites results in the production of an aqueous leachate containing compounds having low biodegradability, high toxicity, and a high organic load. For this reason, this study aims to investigate the applicability of electro-Fenton (EF) and photoelectro-Fenton (PEF) processes as alternative for treating a local landfill effluent with high organic content (chemical oxygen demand (COD) = 2684.7 mg-O 2 L −1) in a continuous-flow reactor (using, for first time, this kind of system with higher electrodes area of 35 cm2) using boron-doped diamond anode (Nb/BDD) and a carbon felt cathode (FC) electrodes. The effects of current density j (30, 60 and 90 mA cm−2) and UV radiation wavelength (UVA and UVC) were studied to evaluate the treatment efficiency as well as the energy consumption. Results clearly showed that, the best efficiencies removing organic matter, in terms of COD, were about 66%, 68% and 89% with an energy consumption of only 19.41, 17.61 and 17.59 kWh kg COD−1 for EF, PEF-UVA and PEF-UVC respectively, at 90 mA cm−2 after 4 h of operation. The treatment of this kind of effluent produced organic and inorganic by-products, the acetic and formic acids as well as NO 2 −, NO 3 −, and NH 4 +, being assessed their concentrations. [Display omitted] • Photoelectro-Fenton (PEF) processes significantly remove organic matter from landfill leachate effluent. • Landfill wastewater can be treated by Electro-Fenton, but it can be improved with irradiation. • Between PEF UVA and PEF UVC approaches, the last one was better on COD removal. • PEF UVC system removed 89.1% of COD and 89.9% of TOC at 90 mA cm−2. • PEF UVC energy requirements are competitive with other electrochemical technologies. [ABSTRACT FROM AUTHOR]

Heteroatom-doped carbon materials can effectively activate H 2 O 2 into •OH during the metal-free electro-Fenton (EF) process. However, information on bifunctional catalysts for the simultaneous generation and activation of H 2 O 2 is scarce. In this study, O- and F-doped porous carbon cathode materials (PPCs) were prepared by the direct carbonization of polyvinylidene fluoride (PVDF) for sulfamerazine (SMR) removal in a metal-free EF process. The porous structure and chemical composition of the PPCs were regulated by the carbonization temperature. PPC-6 (carbonized at 600 °C) exhibited optimal electrocatalytic performance in terms of electrochemical H 2 O 2 generation and activation owing to its high specific surface area, mesoporous structure, and optimum fractions of doped O and F. Excellent performance of the 2e− oxygen reduction reaction was found with an H 2 O 2 selectivity of 93.5% and an average electron transfer number of 2.13. An H 2 O 2 accumulative concentration of 103.9 mg/L and an SMR removal efficiency of 90.1% were achieved during the metal-free EF process. PPC-6 was able to stably remove SMR over five consecutive cycles, retaining 92.6% of its original performance. Quantitative structure-activity relationship analysis revealed that doped oxygen functional groups contributed substantially to H 2 O 2 generation, and semi-ionic C–F bonds with high electronegativity were the cause of the activation of H 2 O 2 to •OH. These findings suggest that the PVDF-derived carbonaceous catalysts are feasible and desirable for metal-free EF processes. • O- and F-doped porous carbon (PPCs) were prepared as bifunctional catalysts. • PPC-6 (carbonized at 600 °C) exhibited the optimal metal-free EF performance. • 90.1% of SMR was effectively removed in the metal-free EF process. • Quantitative structure-activity relationship revealed the role of doped O and F. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the degradation and removal of direct yellow 9 (DY9) by the electro-Fenton (EF) process in batch reactor using iron and stainless steel electrodes. DY9 removal decreased with the increase in pH (3 to 8) and increased with the increase in current intensity (0.05 to 0.2 A) and [H2O2] (0 to 0.5 g L −1 , but not with high doses which led to low rates of DY9 removal and OH ∙ uptake). The regression quadratic models describing DY9 degradation yield “ R (percent)” and electrical energy consumption “EEC (kW h kg −1 )” were validated by the analysis of variance (ANOVA) and were both noted to fit well with the experimental data. The R 2 correlation coefficients (0.995, 0.978), those adjusted coefficients (0.986, 0.939), and F values (110.7, 24.9) obtained for the responses validated the efficiency of model. The results revealed that among several other parameters, EEC depended essentially on the degradation yield. The eco-toxicity tests showed a positive correlation between catalase activity and DY9 concentration, and catalase could be qualitatively identified to assess the effect of dye and its by-products generated during the EF process. [ABSTRACT FROM AUTHOR]

A fruit processing wastewater was submitted to different advanced oxidation processes, namely, electro-Fenton (EF), electrochemical oxidation (EO), activated persulfate (PS), and combined EF/PS. The performance of the treatment processes, at different experimental conditions, regarding organic load removal, biodegradability increment, toxicity reduction, and specific energy consumption (E sp), was evaluated. At the experimental conditions studied, EO led to the treated solutions with the highest biodegradability increment, from 0.24 to 0.48, and toxicity reduction towards Daphnia magna , from 5.8 to 1.5 toxic units, without requiring the addition of chemicals. Nevertheless, the highest chemical oxygen demand (COD) removals were obtained for EF and combined EF/PS treatments. For the electrochemical processes, an increase in COD removal rate with applied current density (j) was observed. However, the increase in j substantially raised the E sp. In PS treatment, COD removals above 80% were only achieved for high amounts of added persulfate and iron, which led to less biodegradable and more toxic solutions. Combined EF/PS attained the lowest E sp values, mainly due to the conductivity increase originated by the persulfate and iron salts addition. Besides the disadvantage of the chemicals added, this combined treatment led to treated solutions with very acidic pH and significant iron content. [Display omitted] • Electrooxidation at BDD promoted the highest reduction in toxicity. • EF and EF + PS treatments led to the highest organic load removals (>90%). • Higher current densities induce higher toxicity abatement. • Combined PS/EF promotes lower energy consumptions, but effluents with high [SO 4 2−]. [ABSTRACT FROM AUTHOR]

The degradation of emerging contaminant coumarin was separately investigated in anodic, electro-Fenton and subcritical water oxidation processes. With respect to the anodic and electro-Fenton oxidation, the influence of constant current, treatment time and initial concentration of coumarin was studied. Regarding subcritical water oxidation, the effect of the oxidant concentration, temperature, treatment time and initial coumarin concentration was investigated. In anodic and electro-Fenton oxidation processes, coumarin degradation proceeded in a similar manner, achieving 99% degradation, after 180 min at a constant current of 200 mA. In both set-ups, further increasing the applied current lowered the degradation efficiency due to the formation of by-products and the increasing occurrence of side-reactions. The highest degradation of 88% was achieved in subcritical conditions, specifically at 200 °C, using 150 mM H 2 O 2 and after 37.5 min of treatment. Under subcritical conditions, temperature was the most prominent parameter, followed by the H 2 O 2 concentration. Under all methodologies, increasing treatment time had a small positive effect on coumarin degradation, indicating that time is not the most influential parameter. A comparison of the three methodologies in terms of performance as well as energy consumption and simplicity of operation highlighted the advantages of subcritical water oxidation. • Degradation of coumarin was investigated using three different oxidation processes. • >99% degradation was achieved in anodic and electro-Fenton oxidation processes. • Subcritical water oxidation at 200 °C achieved 88% degradation after 37.5 min. • O -coumaric acid, salicylaldehyde and catechol were intermediate products under subcritical conditions. [ABSTRACT FROM AUTHOR]

This study aims to compare the efficiency of anodic oxidation with electrogenerated H 2 O 2 (AO-H 2 O 2), electro-Fenton (EF), and their association with UV irradiation (photo anodic oxidation (PAO), and photo electro-Fenton (PEF) for the removal of Direct Red 23 from wastewater using a BDD/carbon felt cell in chloride and sulfate medium and in their combination. The effect of the supporting electrolyte was investigated in AO-H 2 O 2 and EF processes. High discoloration efficiency was obtained in chloride media while a higher mineralization rate was achieved in sulfate media. The EF process reached higher total organic carbon (TOC) removal efficiency than AO-H 2 O 2. 90% TOC removal rate was achieved by the EF against 82% by AO-H 2 O 2 in sulfate media. The influence of using the mixt supporting electrolyte formed of 75% Na 2 SO 4 + 25% NaCl was found to have beneficial effect on TOC removal, achieving 89% and 97% by AO-H 2 O 2 and EF, respectively. High currents led to higher mineralization rates while low currents yielded to a higher mineralization current efficiency (MCE%) and lower energy consumption (EC). UV irradiation enhanced process efficiency. Mineralization efficiency followed the sequence: AO-H 2 O 2 < PAO < EF < PEF. The PEF process was able to remove TOC completely at 5 mA cm−2 current density and 6 h of electrolysis with a MCE% value of 16.57% and EC value of 1.29 kWh g−1 TOC removed. • AO, EF, PAO, and PEF were compared for DR23 removal in chloride and sulfate media. • BDD/carbon felt cell achieved efficient discoloration and mineralization. • Combination of chloride and sulfate as supporting electrolyte provided a beneficial effect. • The mineralization follows the order: AO < EF < PAO < PEF. • Complete removal of DR23 was achieved by PEF at low current of 5 mA cm-2. [ABSTRACT FROM AUTHOR]

With the increasingly discharging and inappropriately disposing of antibiotics from human disease treatment and breeding industry, extensive development of antibiotic resistance in bacteria raised serious public health concern. In this work, algal biochar was coated onto the stainless steel mesh, and was employed as cathodic electrode for the degradation of sulfadiazine (SDZ) in an electro-Fenton (EF) system. It was found that algal biochar pyrolyzed at 600 °C with 1:1 KOH achieved best catalytic performance to generate H 2 O 2 via oxygen reduction. Moreover, removal efficiency of SDZ reached 96.11% in 4 h with an initial concentration of 25 μg/mL, under the optimized condition as: initial pH at 3, 50 mM of Na 2 SO 4 as electrolyte and an applied current of 20 mA/cm2. In addition, it was found that the SDZ removal kept at about 96.99% even after four repeated degradation process. Moreover, four possible SDZ degradative pathways during the EF process were proposed according to determined intermediates, model optimization and density functional theory calculation. Finally, acute and chronic biotoxicity of the degradative products against fish and green algae was evaluated, to further elaborate the environmental impact of SDZ after electrochemical degradation. • The best sulfadiazine removal efficiency reached 96.11% in 4 h using biochar coated cathode. • Biochar coated electrode has higher electroactive surface area and lower mass transfer impedance. • Modified cathode was reliable and stable after four repeated sulfadiazine degradation process. • Four possible sulfadiazine degradative pathways during the electro Fenton process were proposed. [ABSTRACT FROM AUTHOR]

A heterogeneous electro-Fenton (hetero-EF) system can effectively broaden the applicable pH range, although the decreased electrogeneration efficiency of H 2 O 2 at elevated pH (especially neutral conditions) is unfavorable for the efficient removal of organic pollutants. Herein, a tannic acid-Fe complex derivative-modified carbon felt (TFD@CF) cathode was prepared for hetero-EF treatment of organic pollutants over a wide pH range. Interestingly, the as-prepared hetero-EF cathode could act as a pH regulator that acidified the solution over a wide pH range. As expected, the TFD@CF cathode exhibited excellent hetero-EF activity for the removal of diverse organic pollutants (such as methyl orange, methylene blue, sulfamerazine, bisphenol A and 2,4-dichlorophenoxyacetic acid) at neutral and even alkaline pH (removal efficiency >90 %). A total of 2.98 kWh kg−1 COD−1 with 83.2 % COD removal could be achieved by the TFD@CF cathode for the treatment of actual textile dyeing secondary wastewater. Electrochemical characterizations proved that the TFD@CF cathode had excellent electrochemical properties with improved electron transfer ability and a well-pronounced Fe(III) electroreductive response. Meanwhile, more acidic groups were newly generated during the electrochemical reaction (an increase of 30.1 %), thus dissociating more H+ into solution. The identification of reactive oxygen species suggested that OH and 1O 2 could be responsible for the removal of organic pollutants in the TFD@CF EF system. These interesting findings may provide new insights into the design of multifunctional hetero-EF cathodes for the removal of refractory organic pollutants. [Display omitted] • TFD@CF cathode was successfully prepared for hetero-EF treatment. • TFD@CF cathode could act as pH regulator to broaden the applicable pH range. • The hetero-EF activity of TFD@CF cathode was proved satisfactory at pH of 3–9. • TFD@CF cathode exhibited improved electron transfer ability compared with raw CF. • OH and 1O 2 were the dominant reactive oxygen species in TFD@CF hetero-EF system. [ABSTRACT FROM AUTHOR]

This study investigated the degradation of the antineoplastic agent 5-fluorouracil (5-FU) widely applied to treat different cancers using different advanced oxidation processes such as electro-Fenton (EF), photocatalysis with TiO 2, and H 2 O 2 -modified subcritical water oxidation. The treatment with the EF process was the most efficient compared to others. Interestingly, in the EF process, the oxidative degradation of 5-FU behaved differently depending on the anode used. At low currents (20 and 40 mA), Pt and DSA anodes performed better than BDD and Ti 4 O 7 anodes. In contrast, at the higher current of 120 mA, the production of heterogeneous hydroxyl radicals (M(•OH)) became important and contributed significantly to the oxidation of 5-FU in addition to homogeneous •OH generated in the bulk solution. These latter have high O 2 -evolution overpotential leading to the high amount of physisorbed M(•OH) compared to Pt and DSA. The oxidative degradation of 5-FU was then performed by titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes, both of which showed a lower degradation efficiency and failed to achieve complete mineralization. Finally, a comparison was performed in laboratory-scale, taking into account the following performance indicators: the degradation efficiency, the mineralization power, the cost of equipment and reagents, and the energy required for the treatment of 5-FU. [ABSTRACT FROM AUTHOR]

A novel binder-free anthraquinone (AQS)/polyaniline (PANI) modified carbon felt (CF) cathode for selective H 2 O 2 generation and efficient pollutant removal in electro-Fenton was fabricated by CV electro-deposition method. AQS, the oxygen reduction reaction (ORR) catalyst, was immobilized by the PANI film, which contributed to the obtained high stability of the AQS/PANI@CF cathode. The concentration of the electro-generated H 2 O 2 on AQS/PANI@CF cathode (83.3 μmol L−1) was about 10 times higher than that of the bare CF cathode. And the high yield of H 2 O 2 was attributed to the catalytic reduction of O 2 by AQS to generate more superoxide radical (O 2 •-), which combined with H+ to form H 2 O 2. Additionally, the rhodamine B (RhB) degradation efficiency reached 98.8% within 60 min with the AQS/PANI@CF served as the cathode with high stability and good repeatability. The main generated reactive radicals were determined by the quenching experiments and the electron paramagnetic resonance (EPR) tests. Besides, a plausible mechanism of the AQS/PANI@CF cathode applied electro-Fenton process was proposed. This work provided a reliable reference for the subsequent investigations of the binder-free cathode with high performance and stability. [Display omitted] • A novel anthraquinone/polyaniline coated carbon felt (AQS/PANI@CF) was prepared. • The AQS/PANI@CF cathode could enhance the yield of the electro-generated H 2 O 2. • The AQS/PANI@CF cathode has high performance and stability in electro-Fenton. • Mechanism of the AQS/PANI@CF cathode applied in electro-Fenton was proposed. [ABSTRACT FROM AUTHOR]

The removal of trace antibiotics from the aquatic environment has received great interest. In this investigation, NaOH activated graphite felt (NaOH-GF) was characterized by multiple-methods, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle, linear sweep voltammetry (LSV) and electron paramagnetic resonance (EPR). The NaOH-GF was then used as the cathode in the electro-Fenton process for oxytetracycline (OTC) degradation, the experiment was carried out in an undivided and light-proof beaker with a Pt anode and a NaOH-GF cathode at pH 3. The results showed that the modification with NaOH enhanced the antibiotics degradation efficiency of graphite felt by increasing the oxygen reduction capacity and hydroxyl radicals yielding rate. Complete OTC removal was achieved at 5.17 mA cm−2 after 40, 60 and 90 s with initial OTC concentration of 22, 44, and 66 μM, respectively. With an initial OTC concentration of 44 μM, after 30 min the removal rates of chemical oxygen demand (COD) by Raw-GF and NaOH-GF were 59.18% and 83.75%, respectively. The proposed degradation mechanism of OTC was an EF process, which consisted of hydroxylation, secondary alcohol oxidation, demethylation, decarbonylation, dehydration and deamination. This study demonstrates that NaOH activated GF cathode possesses high degradation capacity and good stability. It provides insight into the removal of non-biodegradable antibiotics and may shed light on future to its practical application. Image 1 • Cathode of graphite felt activated by NaOH promoted Oxytetracycline removal. • Decay of OTC with low concentration agrees with a pseudo-first-order kinetics. • Hydroxyl radicals produced in electro-Fenton process was captured by EPR. • Six degradation pathways of OTC were detected in special order by electro-Fenton. [ABSTRACT FROM AUTHOR]

In the present study, the potential of Azolla filiculoides (A. filiculoides) was first investigated for degradation of Phenazopyridine (PhP), an analgesic drug. The effects of main variables such as initial pharmaceutical concentration, amount of plant, and pH were studied on the efficiency of the biological process. It was observed that A. filiculoides was able to remove pharmaceuticals from contaminated water up to 85.90% during 48 h. Then, the electro-Fenton (EF) method was applied for further removal of PhP yielding a removal rate of about 98.72% under optimum conditions during 2 h. The effects of variables including the current, amount of catalyst, and pH were also studied in this phase. Also, the probability of adsorption was investigated during this step. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were performed for the used magnetite nanoparticles, total organic carbon (TOC) were performed to investigate PhP removal efficiency during the reaction time and Gas chromatography–mass spectrometry (GC-MS) were performed to analyze degradation byproducts of PhP. Based on the results, it was found that a combination of these bioremediation and electrochemical removal steps were capable of PhP removal from contaminated water. Therefore, this approach may be effective for phytoremediation of pharmaceutical-contaminated aquatic ecosystems. Image 1 • Biological and Electro-Fenton methods were merged for PhP removal. • Azolla filiculoides was used as phytoremediator and Electro-Fenton method used for further removal of PhP. • Effect of operational parameters during the process were examined. • High decolorization and degradation efficiency of PhP was observed using graphite electrodes. • Degradation byproducts of PhP were identified using GC-MS method. [ABSTRACT FROM AUTHOR]

This study deals with the development of efficient and economic electrochemical treatment processes to confront the treatment of liquid wastes containing non-polar organochlorine pesticides. In previous works, it was demonstrated that it is possible to use electrocoagulation (EC) as a concentration technique for a model organochlorine pesticide (oxyfluorfen). Within this framework, the present work describes a process for the degradation of wastes containing non-polar organochlorines (oxyfluorfen or lindane) in two consecutive stages: 1) a first stage of concentration by electrocoagulation; 2) a second stage of electrochemical degradation by electro-oxidation (EO) or electro-Fenton (EF). The first result reached in the present work is that it is possible to remove close to 50% of both pollutants using EO and more that 94% using EF. Additionally, it was proved that the addition of a pre-concentration stage decreases by a factor of 20 the power consumption needed to deplete by EO the same amount of the initial pollutant. Moreover, when EF process is performed to the concentrated stream, the power consumption is further reduced, getting values (for 1-log removal) as low as 14.51 kWh m−3 for oxyfluorfen decrease and 49.7 kWh m−3 for lindane. These results strengthen the fact that the removal efficiency increases with the concentration of the pollutant and demonstrate that the combination of concentration steps and electrochemical degradation technologies is an efficient and promising alternative for the degradation of non-polar organochlorines. Image 1 • A concentration step reduces by 20 the specific power consumption. • The electric energy per order is 14.5 kWh m−3 for oxyfluorfen decrease. • The electric energy per order is 49.7 kWh m−3 for lindane decrease. • The process allows maximum removal degrees of 94% for both oxyfluorfen and lindane. [ABSTRACT FROM AUTHOR]

Nano-layered double hydroxide (NLDH) decorated with Fe and Cu was applied as a novel heterogeneous catalyst for catalytic degradation of gentamicin by the electro-Fenton (EF) process. The EF process was equipped with graphite plate under aeration to electrochemically generate hydrogen peroxide in the solution. The characterization analyses confirmed the suitable structure of as-synthesized Cu-Fe-NLDH to be acted as catalyst for treating the target pollutant. The comparative study showed the highest removal efficiency of 91.3% when the Cu-Fe-NLDH-equipped EF process was applied in comparison with the Fenton (50%) and the electro-oxidation alone (25.6%). The acidic pHs favored the degradation of gentamicin. Increasing the current resulted in the enhanced degradation of gentamicin, while the excessive electrolyte concentration (0.1 mol/L) and catalyst dosage (1.5 g/L) led to the tangible drop in the reactor performance. At a specified reaction time, the injection of O 3 gas enhanced the efficiency of the Cu-Fe-NLDH-equipped EF process. The presence of ethanol led to more suppressing effect than benzoquinone, indicating the dominant role of OH radical in the degradation of gentamicin compared with other free radical species such as O 2 - radical. Only 10% drop in the degradation efficiency of gentamicin was observed within 10 operational runs. The mineralization efficiency of about 77% was achieved after 300 min in terms of chemical oxygen demand (COD) removal. The intermediate byproducts generated during the destructive removal of gentamicin were also identified. Heterogeneous electro-Fenton process using Cu-Fe-NLDH for degradation of gentamicin. Image 1 • Preparation of Cu-Fe-NLDH using facile hydrothermal method. • Degradation of Gentamicin through electro-Fenton process using Cu-Fe-NLDH catalyst. • Study of catalytic activity of Cu-Fe-NLDH under different operational conditions. • Reusability of Cu-Fe-NLDH catalyst over ten repeated runs. • In situ generation of H 2 O 2 and its conversion to.•OH radicals over Cu-Fe-NLDH. [ABSTRACT FROM AUTHOR]