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The pollution of the aquatic environment by the increasing presence of the non-biodegradable analgesic tramadol (TRA) is increasing due to its high consumption and incomplete elimination in conventional wastewater treatment processes. The aim of the present study is, firstly, to evaluate the oxidative degradation of TRA by the 'electro-Fenton' process, EF for short, at pH 3 (optimal operating pH) for 6 h at a constant current between 60 and 400 mA. Secondly, the possibility of coupling biological treatment with EF will be investigated in order to minimise energy input and increase the profitability of the treatment process. The experimental results showed a considerable mineralisation rate of TRA of over 94% after 6 h of electrolysis at an applied current of 300 mA and a Fe2+ catalyst concentration of 0.1 mM. The TRA degradation in this process followed pseudo-first order kinetics. Several TRA intermediates were identified by LC-MS/MS analysis. A likely reaction pathway for the process of mineralisation was suggested. Combining the EF process with biological post-treatment reduces the energy consumption by more than 66% and increases the economic viability of TRA mineralisation. [ABSTRACT FROM AUTHOR]

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]

The presence of refractory micropollutants in natural waters poses significant environmental and health risks. Preferably, advanced oxidation techniques like electro-Fenton (EF) and bio-electro-Fenton (BEF) are used to mitigate micropollutants; nevertheless, their field-scale implementation is limited by prohibitive catalyst cost. As an alternative, waste-iron electrocoagulated algal biomass (A-BC/Fe) was explored as a heterogeneous Fenton catalyst to eliminate dimethyl phthalate (DMP) from wastewater. The Fenton-conducive morphological, chemical, and electrochemical properties of the A-BC/Fe catalyst were revealed by detailed characterisation. In EF treatment, 10 mg/L of DMP was completely degraded within 15 min at pH of 7.0, 50 mM Na2SO4, and cathode potential of − 1.4 V vs. Ag/AgCl. Moreover, the EF system achieved 87.80 ± 2.10% and 96.14 ± 1.10% of DMP removal from secondary and tertiary treated municipal sewage, respectively. The A-BC/Fe catalyst-driven EF process disintegrated DMP into benign non-toxic by-products and showed stable performance over eight batch cycles with only a 1.71% decline in DMP removal efficiency. Further, the A-BC/Fe-catalysed BEF system eliminated 94.81 ± 1.90% of DMP in 4 h while achieving a maximum power density of 124.03 ± 5.64 mW/m2. This investigation underscores the potential of repurposing electrocoagulated algal biomass as a sustainable heterogenous catalyst for micropollutant remediation. [ABSTRACT FROM AUTHOR]

• A novel side-aerated reactor for in-situ H 2 O 2 electrosynthesis was designed. • Side-aerated reactor coupled with a composite cathode greatly improved H 2 O 2 production. • Different aeration system and cathodes were evaluated for comparison. • Key factors for in-situ H 2 O 2 electrosynthesis were determined. The active graphite felt (GF) catalytic layer was effectively synthesized through a wet ultrasonic impregnation-calcination method, modified with CB and PTFE, and implemented in a pioneering side-aeration electrochemical in-situ H 2 O 2 reactor. The optimal mass ratio (CB: PTFE 1:4) for the modified cathode catalytic layer was determined using a single-factor method. Operating under optimum conditions of initial pH 5, 0.5 L/min air flow, and a current density of 9 mA/cm2, the system achieved a remarkable maximum H 2 O 2 accumulation of 560 mg/L, with the H 2 O 2 production capacity consistently exceeding 95 % over 6 usage cycles. The refined mesoporous structure and improved three-phase interface notably amplified oxygen transfer, utilization, and H 2 O 2 yield. Side aeration led to an oxygen concentration near the cathode reaching 20 mg/L, representing a five-fold increase compared to the 3.95 mg/L achieved with conventional bottom aeration. In the final application, the reaction system exhibited efficacy in the degradation of landfill leachate concentrate. After a 60-minute reaction, complete removal of chroma was attained, and the TOC degradation rate surpassed 60 %, marking a sixfold improvement over the conventional system. These results underscore the substantial potential of the system in H 2 O 2 synthesis and environmental remediation. [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]

Erythrosine B (EB) is a dye widely used in the food and textile industries. Despite many studies that have been proposed in the literature about the electrochemical oxidation of dyes, few studies considered such recalcitrant xanthene compound, although it has been recognized as a threat to health and the environment. Then, this study investigates the oxidation of EB by a homogeneous electro-Fenton process using iron (II) sulfate heptahydrate as a catalyst, carbon felt cathode, and Ti/RuO2 anode. The treated synthetic wastewater contains 100 mg L−1 of EB and has a pH = 3. The effects of three independent variables have been considered for process optimization, such as applied current intensity (0.1–0.5 A), iron concentration (1–10 mM), and stirring rate (100–1000 rpm). Their interactions were investigated considering response surface methodology (RSM) based on Doehlert design as optimization method. EB removal efficiency and energy consumption were considered as model responses after 30 min of electrolysis. Analysis of variance (ANOVA) revealed that the quadratic model was adequately fitted to the experimental data with R2 (0.9819), adj-R2 (0.9276), and low Fisher probability (< 0.0181) for the EB removal model, and R2 (0.9968), adj-R2 (0.9872) and low Fisher probability (< 0.0014) relative to the energy consumption model, suggesting a robust statistical significance. The energy consumption model significantly depends on current density, as expected. The foregoing results obtained by RSM led to the following optimal conditions for EB degradation: current intensity of 0.2 A, iron concentration of 9.397 mM, and stirring rate of 500 rpm, which gave a maximum decolorization rate of 98.15% with a minimum energy consumption of 0.74 kWh m−3 after 30 min of electrolysis. The competitiveness of the electro-Fenton process has been confirmed by the literature analysis proposed as well as by the preliminary economic analysis proposed in the second section of the study. [ABSTRACT FROM AUTHOR]

Textile wastewater, laden with persistent dyes and non‐biodegradable organics, poses a challenge for treatment in common effluent treatment plants (CETPs) using conventional methods. Pre‐treatment of textile effluents is essential to ensure compatibility with CETPs. The present study employed three‐dimensional (3D) aluminum and graphite electrodes for a sequential electro‐coagulation and electro‐Fenton (EC + EF) process. An experimental plan of 25 experiments was constructed using Taguchi method. The combination resulted in high removal efficiencies: 99.91% for color, 93.20% for chemical oxygen demand (COD), and 91.75% for total organic carbon (TOC) for the operating parameters; for EC, current density (J): 20 mA/cm2, time (t): 45 min, speed of rotation (N): 55 rpm; and for EF, current density (J): 25 mA/cm2, time (t): 50 min, iron concentration: 40 mg/L. Post‐treatment, the wastewater exhibited an enhanced biodegradability index of 0.875, rendering it suitable for CETPs. There was an increase of 11% in the total energy consumption when energy spent during rotation and aeration at the time of EC and EF, respectively, were considered. This energy increases the cost and is not accounted for, in previous research. The energy consumption in kWh per g of COD removed at optimum condition for the hybrid treatment was 0.0314, which is lower than the energy consumption by other electrochemical processes employing plate electrodes. This indicates that 3D electrodes are more energy efficient than plate electrodes. Practitioner Points: Hybrid electrochemical processes can be used as pre‐treatment method for textile effluents.Three‐dimensional electrodes improve removal rates with lower energy consumption.Significant color, COD, and TOC abatement were noted post‐hybrid treatment of textile wastewater.Biodegradability of the textile effluent improves after the hybrid treatment. [ABSTRACT FROM AUTHOR]

Electro-Fenton (EF) technology has shown great potential in environmental remediation. However, developing efficient heterogeneous EF catalysts and understanding the relevant reaction mechanisms for pollutant degradation remain challenging. We propose a new system that combines aluminum–air battery electrocoagulation (EC) with EF. The system utilizes dual electron reduction of O2 to generate H2O2 in situ on the air cathodes of aluminum–air batteries and the formation of primary cells to produce electricity. Tetracycline (TC) is degraded by ·OH produced by the Fenton reaction. Under optimal conditions, the system exhibits excellent TC degradation efficiency and higher H2O2 production. The TC removal rate by the reaction system using a graphite cathode reached nearly 100% within 4 h, whereas the H2O2 yield reached 127.07 mg/L within 24 h. The experimental results show that the novel EF and EC composite system of aluminum–air batteries, through the electroflocculation mechanism and ·OH and EF reactions, with EC as the main factor, generates multiple •OH radicals that interact to efficiently remove TC. This work provides novel and important insights into EF technology, as well as new strategies for TC removal. [ABSTRACT FROM AUTHOR]

A study of the degradation of diclofenac (DCF) in an electrochemical reactor equipped with two carbon cloth (CC) electrodes operating in recirculation mode, is presented. The analysis of the effects of the operating variables on the degradation of the DCF showed that, as expected, the applied voltage has a direct influence on the reactions that take place at the anode and cathode. In fact, the addition of O2 and Fe(II) to the medium demonstrated that the electro-Fenton (EF) process was taking place and that under the following conditions, 4 V, 0.05 M Na2SO4, 50 mg/L DCF, 0.25 g Fe(II)-loaded resin, and 50 mL/min, 79.8% of DCF mineralization was obtained in a process described by a pseudo-first order kinetics (k = 0.0184 min−1). Using a simulated domestic wastewater effluent, the EF reactor under study not only showed a similar DCF mineralization value (81.8%), but also reasonable energy consumption (2.16 kWh/m3) as well as CC electrode stability upon several treatment cycles. These results suggest that an EF approach using low-cost CC electrodes and neutral pH conditions, constitute a technically and economically viable option for DCF wastewater treatment. [ABSTRACT FROM AUTHOR]

The inertness of carbon felt as cathode is still one of the challenges encountered in the degradation of pollutants by electro-Fenton. In this study, we used a simple ultrasonic oxidation method to introduce oxygen-containing groups and defect carbons on carbon felt surface to improve the electro-Fenton performance. The modified carbon felts were prepared by ultrasonic treatment in three dilute solutions of HNO3, H2SO4, and HNO3–H2SO4. Ultrasound can provide an extra energetic environment to accelerate the oxidation process, while NO3− has stronger oxidation properties in the presence of excess H+, greatly increasing the amounts of C–O–C/C=O and C–C active sites on carbon felt surface. And an electro-Fenton system with modified CF as the cathode was used to degrade rhodamine B, and the factors affecting the degradation were discussed. The results showed that the modified cathode material was significantly more efficient in degrading rhodamine B, under the conditions of O2 flow rate of 0.3 L min−1, pH = 3, voltage of − 0.7 V, and addition of 0.2-mM Fe2+, HNO3–H2SO4 solution modified CF with 37% higher than that of the raw CF, and the decolorization rate reached 96% after 120 min. Modified carbon felt still has good degradation properties after 5 cycles. The CF was modified by ultrasonic oxidation technique to introduce oxygen-containing functional groups and C-sp3 on the surface of the carbon felt.Using this CF as a cathode for the degradation of RhB in an electro-Fenton system. [ABSTRACT FROM AUTHOR]

• Electro-Fenton was integrated with membrane distillation for VOCs interception. • An oxidation barrier containing ·OH was constructed at the gas-liquid interface. • More than 90% phenol and other by-products were successfully intercepted. Membrane distillation (MD) is a promising alternative desalination technology, but the hydrophobic membrane cannot intercept volatile organic compounds (VOCs), resulting in aggravation in the quality of permeate. In term of this, electro-Fenton (EF) was coupled with sweeping gas membrane distillation (SGMD) in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface, so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate. During the so-called EF-MD process, an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface. It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L. Effective interceptions can be achieved in a wide temperature range, even though the permeate flux of phenol was also intensified. The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions, which endowed the long-term stability of the system. This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

The electro-Fenton process is a state-of-the-art water treatment technology used to remove organic contaminants. However, the low O2 utilization efficiency (OUE, <1%) and high energy consumption remain the biggest obstacles to practical application. Here, we propose a local O2 concentrating (LOC) approach to increase the OUE by over 11-fold compared to the conventional simple O2 diffusion route. Due to the well-designed molecular structure, the LOC approach enables direct extraction of O2 from the bulk solution to the reaction interface; this eliminates the need to pump O2/air to overcome the sluggish O2 mass transfer and results in high Faradaic efficiencies (~50%) even under natural air diffusion conditions. Long-term operation of a flow-through pilot device indicated that the LOC approach saved more than 65% of the electric energy normally consumed in treating actual industrial wastewater, demonstrating the great potential of this system-level design to boost the electro-Fenton process for energy-efficient water remediation. [ABSTRACT FROM AUTHOR]

This study investigated the oxidation of wastewater generated during the production of glass fiber manufacturing material, which contains high organic carbon (18.32 g/L) and has a pH of 8.8, by chemical coagulation, electrocoagulation and electroadvanced oxidation techniques. It was determined that the total organic content (TOC) of wastewater was reduced by 53% using the chemical coagulation method. After electrocoagulation with Al/Al electrode pair for 300 minutes at 500 mA, 73% TOC removal was achieved at pH 8.8. While 50% TOC removal was completed in 2 h at 400 mA in electrocoagulation with Fe/Fe electrode pair, 71% TOC removal was obtained in the combined electrocoagulation/electro-Fenton process by adding hydrogen peroxide to the medium under the same conditions. In addition, it was also observed that the success of the anodic oxidation methods alone was lower. The electro-Fenton application after electrocoagulation was effective and provided 78% TOC but required work at pH 3 and a longer treatment time. [ABSTRACT FROM AUTHOR]

The treatment of slaughterhouse wastewater is a complex task demanding careful consideration due to its challenging nature. Therefore, exploring more sustainable treatment methods for this particular type of wastewater is of utmost significance. This research focused on the impact of electrode materials, specifically graphite and titanium, on the efficiency of microbial fuel cells (MFCs) and electro‐Fenton systems in treating slaughterhouse wastewater. Both graphite and titanium electrodes displayed increasing current density trends, with titanium outperforming graphite. Titanium showed superior electron transfer and current generation (2.2 to 21.2 mA/m2), while graphite ranged from 2.4 to 18.9 mA/m2. Titanium consistently exhibited higher power density, indicating better efficiency in converting current to power (0.059 to 22.68 mW/m2), compared to graphite (0.059 to 12.25 mW/m2) over the 48‐h period. In removal efficiency within the MFC system alone, titanium exhibited superior performance over graphite in key parameters, including zinc (45.5% vs. 37.19%), total hardness (39.32% vs. 29.4%), and nitrates (66.87% vs. 55.8%). For the electro‐Fenton system with a graphite electrode, the removal efficiency ranged from 34.1% to 87.5%, with an average efficiency of approximately 56.2%. This variability underscores fluctuations in the efficacy of the graphite electrode across diverse wastewater treatment scenarios. On the other hand, the electro‐Fenton system employing a titanium electrode showed removal efficiency values ranging from 26.53% to 89.99%, with an average efficiency of about 68.4%. The titanium electrode exhibits both a comparatively higher and more consistent removal efficiency across the evaluated scenarios. On the other hand, the integrated system achieved more than 90% removal efficiency from most of the parameters. The study underscores the intricate nature of slaughterhouse wastewater treatment, emphasizing the need for sustainable approaches. Practitioner Points: Microbial fuel cell (MFC) and electro‐Fenton were investigated for slaughterhouse wastewater treatment.The MFC microbial activity started to decrease after 24 h.The integrated system achieved up to 99.8% removal efficiency (RE) for total coliform bacteria.Up to 99.4% of RE was also achieved for total suspended solids (TSS).The integrated system highly improved RE of the pollutants. [ABSTRACT FROM AUTHOR]

In this work, hydrogen peroxide (H 2 O 2) is produced using an optimized electrochemical cell equipped with a gas diffusion electrode (GDE) as cathode, reaching efficiencies as high as 20.1%, when operating in a single compartment configuration, which increases up to the range 50–60, when a proton exchange membrane is used to separate the anodic and cathodic compartments, pointing out the great significance of the anodic oxidation of H 2 O 2 and the scavenging effects of the oxidants produced on the anode surface. As compared to previous materials tested, the GDE implemented in this cell underwent a more sustainable manufacturing procedure and exhibited an outstanding performance. The H 2 O 2 produced electrochemically is dosed to the real leachate of an industrial dump, strongly polluted with derivatives of lindane. This waste is associated to the operation of a large facility in the seventies and contains different isomers of hexachlorocyclohexane and other chlorinated hydrocarbons, produced during the ageing of the dump. Effects of the addition of iron (II) sulfate salts and irradiation of UVC were also evaluated. All electrochemically-assisted technologies evaluated (named as chemical (EACO), Fenton (EAFO), photolysis (EAPO) and photo-Fenton (EAPFO) oxidations) were able to successfully remove the pollutants, although with important differences in the efficiencies reached. Results demonstrate that EACO, that is, oxidation by molecular H 2 O 2 is the most effective treatment for the treatment of this type of wastes, pointing out that activation of H 2 O 2 to hydroxyl radicals, either by electrochemically assisted Fenton or photolysis is not positive for this waste. As well, among the different pollutants contained in the raw waste, removal of hexachlorocyclohexane (HCHs) and non-chlorinated volatile organic compounds (VOCs) stands out (both groups being the primary species contained in the wastes). These results are very important not only because of the outstanding productions of H 2 O 2 reached with the novel approach of electrochemical cell used, but also because of the implications of the mechanistic understanding of the attack of H 2 O 2 species in the design of a full-scale application to remediate this real important problem. [Display omitted] • Improved production of H 2 O 2 with a novel GDE and cell. • H 2 O 2 is produced with efficiencies over 20% in non-divided configurations. • Improved efficiency when using divided cells, with values as high as 50–60%. • Several electrochemical H 2 O 2 based technologies suitable for degradation wastes. • Unexpectedly H 2 O 2 more efficient that hydroxyl radicals in destroying CHCs. [ABSTRACT FROM AUTHOR]

Methylisothiazolinone (MIT) is a commonly used bactericide in wastewater treatment. Residual MIT in wastewater can lead to high environmental risks and toxicity. In this work, an emerging material MXenes has been introduced into the heterogeneous electro-Fenton catalysts to degrade MIT. Ti3C2Tx@Fe3O4, V2CTx@Fe3O4, and Mo2CTx@Fe3O4 were assessed as catalysts for MIT removal. The reasons for the differences among the three catalyst effects were analyzed according to different characterization results. Mo2CTx@Fe3O4 exhibited the best catalytic activity for MIT degradation. At pH = 3, the removal rate of MIT and corresponding chemical oxygen demand of catalyst Mo2CTx@Fe3O4 were 93.41% and 62.46% after 120 min. Among the three catalysts, Mo2CTx@Fe3O4 had larger surface area and porosity. Mo2CTx@Fe3O4 had the highest surface iron content, which meant that Fe3O4 was more easily loaded on the surface of Mo2CTX. What is more, Mo2CTX had the strongest ability to accelerate the regeneration of Fe2+. The durability of Mo2CTx@Fe3O4 was also evaluated. After four cycles, the removal efficiency of MIT only decreased from 92.51% to 89%. This work supports the development of heterogeneous electro-Fenton catalysts and the degradation of MIT. [ABSTRACT FROM AUTHOR]

In this study, a new hybrid system composed of a photo-catalysis (UV/ZnO) process combined with an electro-Fenton (EF) process equipped with a micro porous graphite air diffusion cathode (MPGADC) was used to treat petroleum refinery wastewater (PRW). The hybrid system was operated in a batch recycle mode and its performance was investigated and optimized using a response surface methodology (RSM). Three operating parameters affecting on the removal efficiency (RE%) of chemical oxygen demand (COD) were investigated including current density (2–10 mA/cm2), ZnO dosage (0.05–0.35 g/L), and Fe2+concentration (0.05–0.15 mM). Results showed that the optimum operating conditions can be achieved using a current density of 6.44 mA/cm2, with ZnO dosage of 0.35 g/L, and concentration of Fe2+ ions at 0.05 mM in which RE% of 90.15% was obtained with requiring a total electrical energy consumption (EEC T) of 19.102KWh/m3. Furthermore, analysis of variance (ANOVA) exhibited a high value of determination coefficient (R2) close to 98.24% indicating a satisfactory fit between the obtained regression model and the experimental results. Moreover, ANOVA results revealed that current density has the most significant effect on RE% with a contribution of 52.41% followed by ZnO dosage and Fe 2 + concentration both of them with a contribution of 11.64%. The comparison between the individual photo-catalysis process and hybrid process showed that RE% increases from 77.83% to 90.15% making an enhancement by 15.83% in RE% while EEC T decreased from 27.171to 19.102KWh/m3 making a reduction by 29.7% in EEC T. Hence, combining EF with photo-catalysis process improves the efficiency and reduced the required energy in comparison with the individual photo-catalysis process. Therefore, the combined process could be considered as an alternative, sustainable, green and cost-effective method for treatment of refinery wastewaters. [Display omitted] • A novel photocatalysis-ElectroFenton system was applied successfully for treatment wastewater. • The optimum conditions were: current density of 6.44 mA/cm2, Fe2+concentration of 0.05 mM, Zn O 2 dosage of 0.35 g/l. • A maximum COD removal (RE% = 90.15% %) with a lower energy consumption (EEC T = 19.102kWh/m3) were achieved after operation of 40 min. • Reaction time was the most effective parameter followed by Z n O 2 dosage, Fe2+ concentration, and current density. • EF+UV/ZnO in comparison with UV/ZnO alone results in an enhancement of 15.83% in RE% and a reduction by 29.7% in EEC T. [ABSTRACT FROM AUTHOR]

The Electro-Fenton process is getting a rapid development recently as a novel advanced electro-oxidation technology for the removal of organic pollutants from water. In this work, a three-dimensional (3D) porous Fe 3 N/FeS composite electrode was created from a Fe 2 (SO 4) 3 -based composite ink by the direct-writing 3D printing technology combined with a high temperature heat treatment under ammonia atmosphere. Fe 3 N served as the conductive skeleton of the electrode, while FeS could provide Fe2+ to react with in-situ generated H 2 O 2 in the Electro-Fenton process to generate ·OH radicals. Thus, it could eliminate the need of external ferrous ion addition. The 3D porous Fe 3 N/FeS composite electrode had desired 3D interconnected macro-channels for efficient mass transport and rough rod surfaces to provide more active sites, which resulted in its superior degradation performance on organics than its traditional two-dimensional (2D) plate counterpart. A two-step H 2 O 2 production path was found on the 3D Fe 3 N/FeS composite electrode, which had been found to possess a faster reaction kinetics. It effectively degraded rhodamine B (RhB) within a wide pH range from ∼3 to ∼ 10, demonstrated stable performances in repeated uses, and had low iron ion leaching, all of which were beneficial for its potential applications. Furthermore, it also demonstrated effective degradation performances on antibiotics of amoxicillin (AMX) and tetracycline hydrochloride (TC-HCl) in both deionized (DI) water and tap water matrixes, indicating its potential to solve the emerging contaminant problem in real water treatment practices. [ABSTRACT FROM AUTHOR]

Inspired by the development of single-atom catalysts (SACs), the fabrication of multimetallic SACs can be a promising technical approach for the in situ electro-Fenton (EF) process. Herein, dual-functional atomically dispersed Mo-Fe sites embedded in carbon nitride (C3N5) (i.e., MoFe/C3N5) were synthesized via a facile SiO2 template method. The atomically isolated bimetallic configuration in MoFe/C3N5 was identified by combining the microscopic and spectroscopic techniques. The MoFe/C3N5 catalyst on the cathode exhibited a remarkable catalytic activity toward the three electron-dominated oxygen reduction reaction in sodium sulfate, leading to a highly effective EF reaction with a low overpotential for the removal of organic contaminants from wastewater. The new catalyst showed a superior performance over its conventional counterparts, owing to the dual functions of the dual-metal active sites. Density functional theory (DFT) analysis revealed that the dual-functional 50-MoFe/C3N5 catalyst enabled a synergistic action of the Mo-Fe dual single atomic centers, which can alter the adsorption/dissociation behavior and decrease the overall reaction barriers for effective organic oxidation during the EF process. This study not only sheds light on the controlled synthesis of atomically isolated catalyst materials but also provides deeper understanding of the structure-performance relationship of the nanocatalysts with dual active sites for the catalytic EF process. Additionally, the findings will promote the advanced catalysis for the treatment of emerging organic contaminants in water and wastewater. [ABSTRACT FROM AUTHOR]

A magnetorheological electro-Fenton composite polishing technology was proposed that enables chemical and mechanical "double enhancement" of the machining process to improve processing efficiency. In this process, a novel high-efficiency catalytic oxidation magnetorheological chemical polishing slurry is configured. Frictional wear experiments are carried out in a magnetorheological electro-Fenton environment to study the corrosion mechanism and material removal behavior of electro-Fenton chemical reactions during magnetorheological electro-Fenton compound polishing. Finally, cluster magnetorheological electro-Fenton compound polishing tests are carried out using the optimized parameters. The results show that the •OH generated by the reaction in the friction and wear of the magnetorheological electro-Fenton composite can effectively oxidize GaN in the friction and wear trajectory to produce a loose cracked Ga2O3 corrosion layer. The corrosion effect increases and then decreases as the current increases from 20 to 60 mA; the corrosion effect also shows a trend of increasing and then decreasing when the rate of H2O2 supplementation increases from 0.30 to 0.60 g/min. The best corrosion effect was achieved when the current was 20 mA, and the H2O2 was replenished at a rate of 0.30 g/min, with a mass fraction of 58.6% of the element O on the sample surface. Using silica sol to polish the GaN for 1 h under the same process, magnetorheological electro-Fenton compound polishing can reduce the surface roughness from Ra 2 to 0.8 nm, while ordinary magnetorheological polishing roughness is only reduced to Ra 1.86 nm. A magnetorheological basis combined with electrochemical means to control and enhance the chemical effect can significantly improve the polishing efficiency. [ABSTRACT FROM AUTHOR]

As Fenton reagents, Fe-based amorphous alloys have achieved good results in the treatment of dye wastewater. However, it is rarely reported how to exert the high activity and high adsorption capacity of those amorphous alloys to treat the oily wastewater with more complex components. In this article, Fe78Si8B14 amorphous ribbon was used as the anode and graphite as the cathode to degrade a kind of emulsified oil wastewater by the electro-Fenton (EF) method. The catalytic degradation under such processing parameters as current density, pH values, and H2O2 concentration was investigated. The catalytic performance of the Fe-Si-B amorphous ribbon was characterized by using the degradation efficiency of the emulsified oil wastewater. The water samples before and after degradation by Fe-Si-B amorphous ribbons were examined by infrared spectrophotometry and gas chromatography-mass spectrometer (GC-MS), respectively. The results show that the degradation efficiency of 99.91% is obtained under optimum process conditions of the current density of 30 mA/cm2, pH value of 3, and H2O2 concentration of 20 g/L. Furthermore, all the long-chain organic compounds in the emulsified oil wastewater are decomposed into short-chain organic substances within 40 min of the reaction. Therefore, the EF method with amorphous alloy as anode and graphite as cathode has a good prospect for the degradation of emulsified oil wastewater. Moreover, the obtained results provide a theoretical basis and guidance for the application of amorphous alloy catalysts in practical wastewater remediation applications. [ABSTRACT FROM AUTHOR]

Petrochemical alcoholic wastewater is one of the most pollutant and toxic wastewaters and its treatment has always been associated with a lot of problems for the petrochemical industry. Electro-Fenton process as an efficient technique can be applied to reduce the chemical oxygen demand of an alcoholic effluent prepared by 2-Ethylhexanol (2EH) unit. The Box-Behnken module was used to design the experiments and then evaluate the effect of various parameters during the treatment. The optimum conditions (81.70% for COD removal) were experimentally found at pH of 4.62, reaction time of 61.81 (min), volume ratio of H2O2 to wastewater of 1.52 (ml/l), H2O2/Fe2+ molar ratio of 3.17 and current density 68.17 (mA/cm2). [ABSTRACT FROM AUTHOR]

A low-cost micro porous graphite air diffusion cathode (MPGADC) has been utilized successfully for the in-situ hydrogen peroxide generation via O 2 reduction in 0.05 M Na 2 SO 4. Using a tubular electrochemical reactor with a novel design composed of MPGADC as a cathode and a hollow cylinder porous graphite as an anode, a maximum of 68 mg/ L of H 2 O 2 was produced at a current density of 25 mA/cm2, an air flow rate of 3 L/min, and a pH value of 3. Electro-Fenton (EF) process was adopted to remove the chemical oxygen demand (COD) from the wastewater of Al-Dora petroleum refinery in Iraq using this new style of tubular electrochemical reactor. Based on the response surface methodology (RSM) with Box-Behnken design (BBD), the effect of EF operating parameters on the COD removal was investigated. The optimal conditions for maximizing COD removal efficiency (RE%) with lowering specific energy consumption (SEC) using EF process were determined to be a current density of 6.66 mA/cm2, Fe2+ concentration of 0.80 mM, and an electrolysis duration of 60 min, in which RE% of 94% with SEC of 3.75 kWh/kg COD were achieved. In addition, the results demonstrated that the current density has the greatest influence on the COD removal, followed by electrolysis duration and then Fe2+ concentration. Furthermore, current density has the greatest impact on the specific energy consumption, followed by time, while Fe2+ concentration has a negligible effect. The high R2 value (98.33%) confirmed the goodness of fitting the model equation. These results established the viability of employing the new cathode design for the EF process in treatment of petroleum refinery wastewaters. [Display omitted] • Low-cost micro porous graphite air diffusion cathode was utilized for COD removal from wastewater using electro Fenton. • The effects of various operational parameters on COD removal(RE%) were evaluated and optimized by RSM. • The new cathode generated a maximum of 68 mg/ L of H 2 O 2 at current density of 25 mA/cm2 and air flow rate of 3L/min. • Current density has the greatest influence on the RE%, followed by electrolysis duration and Fe2+ concentration. • The optimal conditions were current density of 6.66 mA/cm2, Fe2+ concentration of 0.80 mM, and 60 min, in which RE% and SEC were 94% and 3.75 kWh/kg COD. [ABSTRACT FROM AUTHOR]

Spent caustic is a highly contaminated wastewater from critical industries with complicated chemistry and different environmental adverse effects. Conventional wastewater remediation approaches are not effective enough for the remediation of spent caustic. Hence in this study, Electro-Fenton (EF) technology as a subsection of Advanced Oxidation Processes (AOPs) was applied for the removal of chemical oxygen demand (COD) in spent caustic effluent. For statistical analysis and experimental design of each factor including H 2 O 2 /COD, current density, pH, and treatment time on the COD removal (response), the Box Behnken Design (BBD) was used. The optimal conditions for operating factors were as the following: H 2 O 2 /COD = 0.73, pH= 5.46, current density = 18.83 mA/cm2 and treatment time= 69.88 min. In these conditions, the actual and predicted COD removal was 93.0% and, 94.38%, respectively. Finally, it concludes that Electro-Fenton technology was reliable and outstandingly efficient for COD removal in spent caustic wastewater. The kinetic studies confirmed that the removal of COD tracked the first-order kinetic model and the constant reaction rate and half-life of COD removal kinetic were 0.0257 min−1 and 27 min, respectively. The operating costs analysis showed that the Electro-Fenton process had lower operating costs and it can be a good opportunity for the treatment of spent caustic wastewater on an industrial scale. The operational cost for this process was found to be 1.562$ M−3kg−1COD removal. [ABSTRACT FROM AUTHOR]

The use of microfluidic electrochemical reactors has been introduced several decades ago, but their application in the field of wastewater treatment is more recent (2010). The parallel development of electrochemical advanced oxidation processes (EAOPs) as promising technologies for effluent treatment make them good candidates to be implemented as thin film cells. This allows favoring the mass transfer, which is particularly interesting for heterogenous electro‐oxidation. Moreover, the energy requirement is reduced, while there is possibility to treat low‐conductivity solutions. This review intends to provide instructions on the main operating parameters to be optimized during the EAOPs treatment. Directions on engineering aspects have been given to overcome the main drawbacks of microreactors, such as fouling, scaling, and low treatment capacity, based on recent encouraging results given in literature. The promising development of hybrid processes that combine electroseparation with electroconversion would also benefit from such reactor designs. [ABSTRACT FROM AUTHOR]

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use of advanced oxidation processes (AOPs) as a powerful tool for the degradation of persistent pollutants. These AOPs are based mainly on the in-situ production of hydroxyl radicals (OH•) generated from an oxidizing agent (H2O2 or O2) in the presence of a catalyst. Among the most studied AOPs, the Fenton reaction stands out due to its operational simplicity and good levels of degradation for a wide range of emerging contaminants. However, it has some limitations such as the storage and handling of H2O2. Therefore, the use of the electro-Fenton (EF) process has been proposed in which H2O2 is generated in situ by the action of the oxygen reduction reaction (ORR). However, it is important to mention that the ORR is given by two routes, by two or four electrons, which results in the products of H2O2 and H2O, respectively. For this reason, current efforts seek to increase the selectivity of ORR catalysts toward the 2e− route and thus improve the performance of the EF process. This work reviews catalysts for the Fenton reaction, ORR 2e− catalysts, and presents a short review of some proposed catalysts with bifunctional activity for ORR 2e− and Fenton processes. Finally, the most important factors for electro-Fenton dual catalysts to obtain high catalytic activity in both Fenton and ORR 2e− processes are summarized. [ABSTRACT FROM AUTHOR]

As an easily obtained organic waste, by-product acetic acid could be an appropriate co-substrate with blue algae wastes (increase C/N ratio of substrates) for co-fermentation of PHA production. However, there are still acrylic acid and other chemicals in by-product acetic acid, which could cause severe inhibition for fermenting microorganisms during PHA production process. The current study represented that alkali pretreatment (pH level of 12) is a more favorable method compared with thermal pretreatment (80 ℃ for 30 min) for breaking cell walls of blue algae. It seemed that there was no synergistic effect of the combination of thermal and alkali pretreatment methods (temperature of 80 ℃ and pH level of 12). Optimal parameters during electro-fenton process for removal of inhibitors in by-product acetic acid were under current of 0.5 A, pH level of 3 and reaction time of 120 min. Both the highest dry weight of PHA and PHA concentration were achieved by applying blue algae and by-product acetic acid (after pretreatment) as co-substrates (mixed ratio of 3:1, stirring speed of 200 r/min, 24 h), indicating that using by-product acetic acid (after pretreatment) as co-substrate could increase C/N ratio and promote PHA production successfully. The current study could offer new insights for improving PHA production by co-fermentation. [Display omitted] • Alkali pretreatment is a more favorable method compared with thermal pretreatment. • There was no synergistic effect of the combination of thermal and alkali pretreatment. • Optimal parameters for removal of inhibitors in by-product acetic acid were determined. • By-product acetic acid (after pretreatment) as co-substrate could promote PHA production. [ABSTRACT FROM AUTHOR]

• Dual-cathode electro-Fenton was realized by coupling CA with Ti cathode. • Cu-organic intermediates possessed higher activity for in situ H 2 O 2 activation. • Enhanced production of Cu(I) by Ti cathode promoted •OH and Cu(III) generation. • •OH was predominant for the decomplexation and Cu(III) played a minor role. Heavy metals that are readily chelated with coexisting organic ligands in industrial wastewaters impose threats to environment and human health but are also valuable metal resources. Traditional treatment methods generally require additional chemicals and generate secondary contaminants. Here, a reagent-free dual-cathode electrochemical system was proposed for the efficient destruction of Cu-organic complexes and synchronous cathodic recovery of Cu, whereby in situ production of H 2 O 2 at carbon aerogel (CA) cathode was coupled with the reduction of Cu(II) to Cu(I) and finally to Cu(0) at Ti cathode. The intermediate Cu(II) complexes enabled the self-reinforced degradation owing to their higher activities toward •OH generation by activating H 2 O 2 in contrast to initial Cu-ethylenediaminetetraacetic acid (Cu-EDTA). The enhanced production of Cu(I) by Ti cathode facilitated both •OH and Cu(III) formation, and the copper redox cycle was realized in the self-reinforced system, maintaining its sustainable catalytic activity. The energy cost of the dual-cathode system is 0.011 kWh/g for decomplexation and 0.057 kWh/g for Cu recovery, which is much lower than single Ti or CA cathode system. This established process provides a prospective approach for cost-effective destruction of chelating metal complexes and metal resources recovery from heavy metal wastewaters. [Display omitted] [ABSTRACT FROM AUTHOR]

• Selective electro-Fenton system was fabricated via cathode-mediated PMS activation. • Microenvironment regulation of atomic Fe inhibits undesirable radical pathways. • Optimal B-FeN 4 CA/PMS system exhibits highest 1O 2 generation of 63.4 μmolL⁻¹min⁻¹. • Preferential removal of sulfonamides was achieved in different water matrices. • Pilot electrochemical device was used to assess the performance in real-scenario. Electro-Fenton technologies driven by peroxymonosulfate (PMS) activation have been extensively explored for abatement of organic pollutants from water. Unfortunately, a great diversity of matrix components in contaminated water scenarios inevitably and significantly compromises the efficiency of the generated radicals toward target pollutants. Thus, selective oxidation of the electro-Fenton technologies is urgently desired for cost effective and sustainable water treatment, but challenged by the traditional electron transfer pathway from cathode to PMS to mainly form SO 4 •− and HO• radicals. In this study, we successfully realized selective generation of 1O 2 , a non-radical species specific for electron-rich pollutants, by regulating the second-shell coordination environment of single-atom Fe in carbonaceous cathode. The doped electron-accepting B drives directional electron transfer from PMS to electrode and inhibiting the undesirable radical pathways. Besides, the electrochemical reduction of H+ in-situ generated from the dissociation of H-O in PMS is favourable for the formation of 1O 2 as high as 163.4 μmol.L−1min−1. Fast and preferential removal of sulfonamides pollutants in different water matrices demonstrated the excellent matrix tolerance of the newly developed electro-Fenton process. A pilot electrochemical device was designed to further selective remove phenols in real-scenario application. No residual phenol was detected (<0.01 mg/L) with TOC removal around 50% (down to 23.9±0.3 mg L−1) during the continuous 24-h operation. This study is also believed to shed new light on how to achieve desirable electrochemical reactions via microenvironmental regulation in response to sustainable water decontamination and beyond. [Display omitted] [ABSTRACT FROM AUTHOR]

• Building an electro-Fenton system based on Fe electrodes and CaO 2 in composting. • The electro-Fenton system promoted more precursors to form humus substances. • Enrichment of electroactive bacteria promoted humification. • The electro-Fenton system reduced CO 2 , CH 4 , and N 2 O emissions. The Fenton-like system and electric field assistance are two novel and efficient strategies to improve traditional composting. However, the coupling impacts of the Fenton-like system and electric field assistance on humification and greenhouse gas emissions in composting are rarely studied. Therefore, this study used an iron plate as the electrode material to construct a new electro-Fenton system by adding CaO 2 particles and evaluated the effects and potential mechanisms of this system on humification and greenhouse gas emissions in composting. The results showed that the electro-Fenton system not only effectively promoted more precursor substances to form humic substances by participating in the Maillard reaction, but also effectively enriched electroactive bacteria such as Bacillus , Geobacillus , and Klebsiella , which facilitated the humification by accelerating electron transfer. In addition, the electro-Fenton system effectively reduced greenhouse gas emissions. In summary, electro-Fenton is an effective strategy to improve humification and reduce greenhouse gas emissions during composting. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrode preparation process and electro-Fenton catalytic mechanism in the N,P-C/B 3 C-EF system. • Monolithic electrode was prepared by a simple green method with biochar as precursor. • N,P-C/B 3 C showed great activity and stability for purification of actual wastewater. • Degradation pathways and toxicity assessment of organic contaminants was revealed. • Synergistic effect of N, P sites was revealed by characterization and calculation. • Prr N-P, Gra N-P, and Prr N-P are conducive to accelerate 2e- ORR and ROS generation. The utilization of renewable carbon resources (waste biomass) and the study of metal-free active components have received much attention in the field of catalysis, also showing great development potential for the preparation of electro-Fenton (EF) electrode material toward the efficient wastewater remediation, but there are still many challenges in the revelation of microstructures regulation and EF catalytic mechanism induced by biochar and metal-free active sites. So, in this work, the monolithic biomass-derived electrode (N,P-C/B 3 C) was prepared by a simple and green strategy, in which the biochar derived from waste bagasse and the heteroatom N, P acted as the carbon-based precursor and the metal-free active sites, respectively. The regulation of electrode microstructure induced by different raw materials was explored. The catalytic performance, stability, energy consumption, toxicity analysis, and organic degradation path in this N,P-C/B 3 C-EF system were investigated in detail by treating simulated wastewater and real pharmaceutical wastewater, respectively. According to experiments, characterization analysis, and density functional theory (DFT) calculation, the enhanced EF reaction mechanism by the synergistic effect of N,P co-coped sites in carbon matrix was revealed, where Prr N-P and Gra N-P structures may be the suitable sites for 2e- ORR process, accelerating the O 2 adsorption and breaking the *–OOH bond to form H 2 O 2. Significantly, Prr N-P possesses the most powerful thermodynamics and the lowest energy barrier toward the rate-determining step (conversion of·H 2 O 2), being the superior active site for H 2 O 2 adsorption and activation to produce strongly oxidizing ROS. [ABSTRACT FROM AUTHOR]

In this study, the efficacy of electrocoagulation (EC), electro-Fenton (EF), and a combined EC/EF approach—in treating real chemical industrial wastewater—was investigated. Optimal conditions for the EC process were identified at an applied current density of 480 mA/cm2 and a duration of 13 min. In contrast, the EF process demonstrated peak performance at a current density of 350 mA/cm2 and a duration of 147 min. Importantly, a consistent supporting electrolyte concentration of NaCl at 3.3 g/L was maintained for both EC and EF treatments. Under these optimized conditions, the EC process showcased superior efficiency in total suspended solids (TSS) removal, achieving an impressive 82.87% removal rate, whereas the EF process yielded a moderate 41.41%. Conversely, the EF process outperformed in organic removal, registering an exceptional 96.83% removal rate compared to the 53.21% achieved by the EC treatment. Remarkably, the sequential application of both EC and EF processes led to the complete removal of TSS and organics, resulting in a CI reduction to zero. Biological testing corroborated the effectiveness of the combined treatment, confirming the water to be 100% sterilized and thereby suitable for both irrigation and potable use. The novelty of this study lies in the sequential application of electrocoagulation (EC) and electro-Fenton (EF) processes, which, for the first time, achieved complete removal of total suspended solids (TSS) and organics from real chemical industrial wastewater, while also sterilizing the water, rendering it suitable for irrigation and potable use. [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]

Heterogeneous electro-Fenton (hetero-EF) technology represents a promising and safe approach to water treatment. However, conventional hetero-EF catalysts still face the challenges of removing contaminants selectively and operating efficient in complex water quality. We proposed a novel system utilizing amorphous CoS x (A-CoS x) that overcame these limitations. This material generated only singlet oxygen (1O 2), a highly specific oxidant, for contaminants degradation. Unlike traditional crystalline catalysts, A-CoS x efficiently utilized hydrogen peroxide (H 2 O 2) to directly produce 1O 2 , exhibiting high catalytic activity across a wide pH range (3.0–11.0). The formation mechanism of 1O 2 was confirmed through experimental investigations, density functional theory (DFT) calculations, and advanced characterization techniques. This system effectively degraded contaminants even in complex water with interferences and enabled selective targeting of pollutants with electron-donating groups. This innovative approach using amorphous materials offers a promising strategy for the regulation of ROS and enabling selective contaminant removal in water treatment. [Display omitted] • The role of amorphous CoS x catalyst for 1O 2 generation in hetero-EF system was revealed. • A-CoS x achieved nearly 100 % H 2 O 2 utilization efficiency and 1O 2 conversion in the hetero-EF system. • The A-CoS x /hetero-EF system demonstrated exceptional efficiency and selectivity in water decontamination. [ABSTRACT FROM AUTHOR]

The treatment of highly concentrated and recalcitrant organic pollutants in industrial wastewater has garnered significant attention, with Fenton oxidation emerging as a promising approach. However, traditional iron-based Fenton reagents present certain limitations, and copper-based Fenton systems are often less efficient. Thus, it is necessary to develop innovative copper-based Fenton catalytic materials. In this study, Cu₂O and Ag-modified activated carbon fibers (Cu₂O-Ag@ACF) were synthesized via liquid-phase reduction. The composition, structure, and morphology of Cu₂O-Ag@ACF were systematically characterized. The Cu₂O-Ag@ACF was employed as a functionalized cathode in the electro-Fenton process to degrade a highly concentrated organic pollutant solution, with methylene blue serving as a model contaminant. The loading of Cu₂O and Ag not only enhances the electrochemical performance of ACF but also improves its Fenton oxidation efficiency. Cu₂O-Ag@ACF exhibited less than 1 % performance degradation after five cycles of use, highlighting its potential for industrial applications under simulated realistic conditions. Moreover, the electro-Fenton system parameters, including current density, pH, electrode spacing, and solution temperature, were optimized. Under the optimal conditions, the degradation rate of methylene blue by Cu₂O-Ag@ACF reached 92.8 % within 120 minutes. Kinetic analysis indicated that the reaction followed a first-order kinetic model, with a rate constant of 0.253 min⁻¹. Furthermore, this study revealed that trace silver doping significantly accelerated the generation of reactive oxygen species, thereby enhancing the efficiency of the Cu-based Fenton-like catalysts. In conclusion, this work presents a convenient strategy for the sustainable and efficient purification of industrial wastewater, contributing to the improvement of human life quality. [Display omitted] • A novel copper-silver hybrid Fenton-like functionalized cathode (Cu₂O-Ag@ACF) was developed. • Cu₂O-Ag@ACF demonstrates significant potential for industrial applications under simulated realistic conditions. • Trace doping with Ag significantly enhanced the generation rate of reactive oxygen species. [ABSTRACT FROM AUTHOR]

Currently, most magnetorheological polishing methods use point or linear scanning. When these methods are applied to large-size semiconductor polishing, they are often limited by efficiency, making it difficult to simultaneously consider the surface quality and processing efficiency. In addition, because the mechanism of magnetorheological polishing is not yet clear, it is difficult to achieve the effect of synergistic enhancement of polishing efficiency and surface quality by simply increasing the magnetic field strength or introducing chemical reactions. In this paper, we propose a new method of combining the flexible force of magnetorheological action with the controllable electro-Fenton chemical action, and experimentally confirm the mechanism of the new skin corrosion effect that occurs under the flexible force applied to the magnetorheological micro-abrasive head, which provides a favorable theoretical research basis for improving the quality and efficiency of magnetorheological polishing. We also simulated the process using a magnetorheological electro-Fenton friction wear device and analyzed the influence of various parameters on the formation of the new skin corrosion effect. The results show that in the case of conventional friction and wear methods failing to form significant material removal corrosion trajectories, the composite friction method of magnetorheological electro-Fenton was able to form a corrosion layer of significant thickness over the entire range of action after the use of magnetorheological electro-Fenton composite friction method. Different third-generation semiconductor materials and crystal directions are presented with very significant corrosion effects. In particular, the best results were obtained when H 2 O 2 was continuously added at a rate of 0.30 g/min, a current parameter of 20 mA, a concentration of 3 wt% diamond particles, and a load of 0.418 N was applied, resulting in a cracked corrosion layer. [Display omitted] [ABSTRACT FROM AUTHOR]

Inspired by the growing development of dual single-atom catalysts (SACs), a bimetallic single-atom alloy (SAA) based macro-assembled graphene aerogel (MAGA) was synthesized in this study. The single-atom NiCo alloy-based graphene aerogel (i.e., NiCo/GO aerogel) with pinning effect was used as a sustainable cathode material in an in-situ H 2 O 2 generation system (i.e., electro-Fenton (EF) process). The atomic structure of NiCo/GO aerogel was identified by the combined microscopic and spectroscopic techniques. The SAA cathode exhibited a remarkable catalytic activity towards the two-electron-dominated oxygen reduction reaction (ORR) with the EF process for wastewater treatment. The energy consumption was calculated to be around 0.660 kW·h/t for treatment of water containing 2 mg L−1 ibuprofen (IBU). Density functional theory (DFT) analysis revealed the specific roles of the dual-functional NiCo SAA in the GO aerogel cathode, i.e., the Co sites more preferentially adsorb O 2 molecules for H 2 O 2 generation while the Ni sites function as the active sites for H 2 O 2 dissociation and activation. The research findings shed light on the controlled synthesis of SAAs for advanced catalysis and its potential application in the treatment of emerging organic contaminants for water safety and pollution control. [Display omitted] • Single-atom NiCo/GO aerogel with pinning effect was used as a sustainable cathode material in an EF system. • The energy consumption was calculated to be around 0.660 kW·h/t for treatment of water containing 2 mg L−1 IBU. • DFT revealed that Co sites were for H 2 O 2 generation, while the Ni sites function as active centers for H 2 O 2 activation. • A flow-through system was established as well. [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]

[Display omitted] • N-doped porous carbon materials (WNPC) were derived by ZIF-8 modified balsa wood. • WNPC showed excellent H 2 O 2 generation capability in electro-Fenton system. • WNPC has a good selectivity for two electron oxygen reduction reaction. • Hydroxyl radicals were the main active substances for efficient TC degradation. Efficient electrochemical advanced oxidation processes (EAOPs) based on carbon catalysts are highly promising candidates for green environmental remediation technologies. Wood derived N-doped porous carbon (WNPC) was prepared the balsa wood with in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) was used as precursor. WNPC acted as self-supporting electric Fenton cathode with high yield and selectivity (96 %) of in-situ H 2 O 2 generation, which effectively avoided the use binder for powder material. Owing to abundant N-doping and oxygen functional groups, the H 2 O 2 yield of WNPC was three times that of balsa wood derived carbon (WC) in electro-Fenton system. The graphite-N promoted the electron transfer, while the pyridinic-N could enhance the selectivity of the 2e-ORR for H 2 O 2 generation. Furthermore, the specific surface area of WNPC was 10 times of WC, with improved hydrophilicity and accelerated electron transfer. The removal efficiency of tetracycline hydrochloride (TC) achieved 91 % within 120 min in electro-Fenton system with WNPC and Fe2+, which was much higher than that with WC (63 %). Free radical scavenging and electron paramagnetic resonance experiments confirmed that ·OH and O 2 –· were the main active substances for TC degradation in electro-Fenton system. In addition, WNPC has good stability, reusability, and comparable degradation performance of various organic pollutants, and also had efficient degradation performance with actual water. This research proposed a novel strategy to construct efficient electro-Fenton catalyst with wood as precursor, which provides an advancing electrocatalytic methods to achieve efficient and environmentally conscious water purification. [ABSTRACT FROM AUTHOR]

Low H 2 O 2 production, narrow adaptive pH range and slow Fe(II) regeneration on the cathode still limit efficiency of electro-Fenton (EF) and its application. Herein, we designed a bifunctional catalyst with FeS and Fe 3 O 4 nanoparticles dispersed on porous carbon (CFeS@C) using template of sodium alginate (SA)/FeSO 4 hydrogel mixed with carbon black (CB), which presented high H 2 O 2 generation efficiency and outstanding tetracycline degradation efficiency under wide pH ranges (3-8) with a low energy consumption of 19.6 kWh/kg total organic carbon (TOC). The introduction of CB created abundant oxygen vacancies in CFeS@C, promoting the oxygen adsorption and the electrochemical generation of H 2 O 2 , which further boosted the formation of •OH due to the interaction with Fe2+ on the cathode surface. Simultaneously, the reaction between the outer layer of FeS and Fe3+ not only accelerated iron cycling but also reduced the solution pH. It was verified that •OH and 1O 2 played a dominant role in organics degradation. The system maintained stability after 10 cycles and effectiveness in the treatment of pharmaceutical wastewater. This study would offer a new strategy to develop an efficient and durable bifunctional catalyst for heterogeneous EF system working in wide pH conditions for wastewater treatment. [Display omitted] • H 2 O 2 generation and multiple reactive species was achieved on FeS/Fe 3 O 4 @C as cathode. • The multi-layered reaction centers of O V , FeS and Fe 3 O 4 promoted pollutants removal. • Radical and non-radical oxidants were produced simultaneously on the cathode. • This system exhibited efficient degradation behavior in wider application pH. • It was promising and stable for removing various pollutants in water/wastewater. [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]

[Display omitted] • Polymerization of phenolic pollutant is initiated by HO• derived from H 2 O 2. • Simultaneous pollution reduction and organic carbon recovery is achieved. • Recyclable suspended solid organic polymers accounts for 53% of the initial COD. • Only requires a quarter of H 2 O 2 consumption compared to degradation process. • Much lower total energy consumption compared to previous Fenton-like processes. Converting organic pollutants into easily recyclable solid polymers has the advantages of saving oxidants and recovering organic carbon, compared to degrading them into smaller organic molecules. Taking o -cresol as a representative phenolic pollutant, this study realizes the dominant reaction of organic polymerization and the recovery of organic carbon from wastewater via a cathode/Fe2+/H 2 O 2 process. With HO• initiation, 53 % of chemical oxygen demand is removed in the form of suspended solid polymers and equivalent organic carbon is recovered. At the same time, the dissolved organic carbon (DOC) removal reaches 64 %, and the H 2 O 2 consumption is only a quarter of that in an ideal degradation process. The recovered solid polymers are oligomers derived from o -cresol and its derivatives, with the molecular weight ranging from 400 to 2500 Da. The polymerization pathway involves repeated HO• oxidation and coupling of intermediate organic radicals. The energy consumption is 26.7 kWh/kg DOC, significantly lower than that of previous Fenton-like processes in the literature. This study broadens the scope of polymerization-based technologies for organic wastewater treatment, and demonstrates that HO• has the potential to simultaneously reduce organic pollution and recover organic carbon by generating suspended solid organic polymers, which may provide new avenues for H 2 O 2 -based Fenton processes toward resource recovery and water purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • 'Dual-catalytic-site' strategy is developed in MoS 2 -based electro-Fenton process. • Fe-MoS 2 HS/GF synchronously remove Cr (VI) and diverse organic pollutants. • Fe-Mo dual sites reduce H 2 O 2 dissociation energy and favor ·OH surface generation. • Electric-driven valence shifts in Fe-Mo sites accelerate Fe (II) regeneration. • Continuous-flow system shows good stability and practical use in real wastewater. Synergy removal of heavy metals and emerging organic pollutants (EOPs) poses a formidable challenge in heterogeneous electro-Fenton processes. Here, we present a three-dimensional iron-doped molybdenum disulfide hierarchical microsphere/graphite felt (Fe-MoS 2 HS/GF) system. This system exhibits exceptional electrocatalytic redox activity, achieving a 9.75-fold and 18.96-fold increase in Cr (VI) (2.38 × 10-2 min−1) and BPA (8.29 × 10-2 min−1) removal rates compared to the MoS 2 HS/GF system, respectively. And it also exhibited a significantly enhanced mineralization efficiency (59.28%) for BPA, surpassing that of the MoS 2 /GF system (5.75%) by a factor of 10.31. Mechanistic insights indicate that the Fe-Mo dual catalytic sites effectively lower reaction barriers of H 2 O 2 dissociation, generating significant amounts of ·OH surface and 1O 2 species for BPA degradation. Moreover, an electric field-driven the variable valence state of the Fe-Mo dual sites facilitates Fe (II) regeneration and Cr (VI) reduction. Notably, this system shows broad applicability for synchronous removal of Cr (VI) and diverse EOPs, exhibiting robust stability under unsteady-state continuous-flow operation (2 L reactor) with reduced biotoxicity in actual wastewater. This study highlights the synergistic benefits of the dual catalytic sites in the heterogeneous electro-Fenton processes for treating multicomponent wastewater. [ABSTRACT FROM AUTHOR]

Emerging contaminants (ECs) are concerned worldwide due to their ubiquitous, persistence, high toxicity and low treatment efficiency in conventional processes. Meanwhile, the electro-Fenton (EF) technique has gained significant attention owing to its high efficiency and environmental compatibility for the degradation of ECs. Nevertheless, the EF process has suffered low Faraday efficiency, high cost and poor mass transfer, mainly in the low efficiency of Fe3+/Fe2+ cycle, insufficient capacity of oxygen reduction and limitation of low pH. The ways to improve EF efficiency include adding catalysts, optimizing electrode materials, and coupling other technologies. Among them, cathode material is the key factor affecting EF efficiency. In recent years, researchers have carried out a large number of related studies, among which carbonaceous materials (CMs) have become one of the most promising EF cathode materials due to their excellent performance advantages. Many works on the preparation and modification of novel carbon materials have been paid attention to, but lacks a systematic review report summarizing carbon cathode in EF process. Aiming at this issue, this paper summarizes the modification of CMs to improve H 2 O 2 electrogeneration, strengthen Fe3+/Fe2+ cycle efficiency, and broaden pH window, respectively. Besides, the development of biochar materials is summarized, and the existing shortcomings and future development directions in the field of cathode EF are briefly discussed. [Display omitted] • Cathode material is a key factor affecting cathode electro-Fenton efficiency. • Various carbonaceous cathodes for emerging contaminants degradation are summarized. • Cathode modification for H 2 O 2 generation, Fe3+/Fe2+ cycle and pH window are reviewed. • The development of biochar materials as electro-Fenton cathode is introduced. • The shortcomings and future research directions for electro-Fenton are proposed. [ABSTRACT FROM AUTHOR]

Introducing the source, water quality and harm of landfill leachate, and introduces an u environment-friendly technology" 一electrochemical method, which can effectively remove refractory and toxic organics in landfill leachate・ Electrochemical technologies in landfill leachate treatment mainly include electrocoagulation, electrooxidation, electro・Fenton and coupling of electrochemical technology with other technologies. Their principles, characteristics, treatment effects and application prospects are analyzed. [ABSTRACT FROM AUTHOR]

The fast and complete removal of the anti-cancer drug cytarabine (CYT) from water was studied, for the first time, by the electro-Fenton process using a BDD anode and carbon felt cathode. A catalytic amount (10−4 M) of ferrous iron was initially added to the solution as catalyst and it was electrochemically regenerated in the process. Complete degradation of 0.1 mM (24.3 mg L−1) CYT was achieved quickly in 15 min at 300 mA constant current electrolysis by hydroxyl radicals (●OH) electrocatalytically generated in the system. Almost complete mineralization (91.14% TOC removal) of the solution was obtained after 4 h of treatment. The mineralization current efficiency (MCE) and energy consumption (EC) during the mineralization process were evaluated. The absolute (second order) rate constant for the hydroxylation reaction of CYT by hydroxyl radicals was assessed by applying the competition kinetics method and found to be 5.35 × 109 M−1 s−1. The formation and evolution of oxidation reaction intermediates, short-chain carboxylic acids and inorganic ions were identified by gas chromatography-mass spectrometry, high performance liquid chromatography and ion chromatography analyses, respectively. Based on the identified intermediate and end-products, a plausible mineralization pathway for the oxidation of CYT by hydroxyl radicals is proposed. [ABSTRACT FROM AUTHOR]

In this study, Firstly, an Electro-Fenton (EF) system was established by converting the biochar products obtained by pyrolysis from the mixed furniture waste biomass to electrodes of without modification (raw) and after thermal modification. The modification variables of biochars were determined as: gas type (N2,CO2), temperature (500-900°C) and time (1-4 h). In the EF system, the effects of modified biochar electrodes used as cathodes on peroxide production-current efficiency (CE) and dye removal efficiency were examined and the most effective biochar electrode and modification conditions were determined. In the study, pH:3, EF time: 0.5 hours, cathodic potential:2 V, catalyst (FeSO4) concentration:0.2 mM, electrolyte (Na2SO4) concentration: 50 mM as EF conditions and Astrazon blue aqueous solution (50 mg/L) were chosen as a model contaminant. Among the electrodes, the most effective electrode was determined as the electrode (CO2-700-1), which was thermally modified in CO2 gas at 700°C for 1 hour. In addition, the energy efficiency and economic results of the study were analyzed. When the electrodes are evaluated in terms of treatment cost for 100% dye removal in the EF system, it is found that the treatment cost obtained with the electrode (CO2-700-1) is 68.2% lower than the raw electrode (N2-350-4). It was observed that the dye removal efficiency of the regenerated electrode did not change after 10 cycles. [ABSTRACT FROM AUTHOR]

A weak aspect of the electro-Fenton (EF) oxidation of contaminants is the dependence of the Fenton reaction on acidic pH values. Therefore, the rationale of this work was to develop a novel catalyst capable of promoting the EF oxidation process at near-neutral and basic pH values. In this framework, rhombohedral FeCO3 was synthesized hydrothermally and used as a catalyst in the EF oxidation of p-benzoquinone (BQ). The catalyst was characterized using various surface and spectroscopic methods. Moreover, the effects of applied current (100–500 mA), time (1–9 h), catalyst dosage (0.25–1.00 g L−1), and initial concentration of BQ (0.50–1.00 mM) on the total organic carbon removal efficiency were determined. The results indicated that a 400 mA current was sufficient for a 95% total organic carbon removal and that the increase in catalyst dosage had a positive effect on the mineralization of BQ. It was determined that at pH 3, FeCO3 behaved like a homogeneous catalyst by releasing Fe3+ ions; whereas, at the pH range of 5–7, it shifted to a homogeneous/heterogeneous catalyst. At pH 9, it worked solely as a heterogeneous catalyst due to the decrease of Fe ions passing into the solution. Finally, the spent catalyst did not undergo structural deformations after the EF treatment at higher pH values and could be regenerated and used several times [ABSTRACT FROM AUTHOR]