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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]

Electro-Fenton process could remove pollutant in in tannery industry wastewater. The objectives of this is used to know the effect of electro-Fenton on, ammonia (NH3), chromium (III) (Cr(III), total suspended solid (TSS), biological oxygen demand (BOD), and chemical oxygen demand (COD) removal in tannery wastewater treatment. The voltage variation used to trigger the electro-Fenton reaction was 6 V, 8 V, and 10 V. Observation time at 0, 30, 60, 90, and 120 mins was used to see changes in the sample. The results obtained are electro-Fenton method has an effective time of 30 mins to removal efficiency of 60.7%, 32.9%, 72.8%, 53.4%, and 53.4% for NH3, Cr(III), TSS, BOD, and COD respectively. Pollution from tannery effluent can be eliminated to a sufficient extent using the electro-Fenton technique. [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]

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]

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]

[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]

Dyes are common pollutants that are found in industrial wastewater including food, pharmaceutical, and cosmetic industries. This study aimed to degrade Ponceau 4R (P4R) by the electro-Fenton (EF) process based on iron electrodes in the aqueous solutions. For the EF process, a 900 mL glass reactor containing two iron electrodes which connected to a power supply was used. The effects of five experimental variables namely applied voltage (5–20 V), electrolyte concentration (0–0.2 mol L−1 Na2SO4), initial P4R concentration (50–250 mg L−1), pH of the solution (2–6), and H2O2 content (0.033–0.100 %v/v) were investigated in four levels and optimized by Taguchi method (OA16). The residual concentrations of P4R after the EF process were spectrophotometrically determined at 505 nm in the time range of 0–90 min with time intervals of 10 min and the removal efficiencies were obtained. Based on the results, the optimum conditions were obtained as pH = 3, voltage = 20 V, H2O2 = 0.033 % v/v, C Na2SO4 = 0.1 M and the CP4R = 50 mg L−1. Under the optimum conditions, about 100% of P4R was removed during 10 min. The energy consumed in the EF process was calculated as 19.82 KWh/m3 during 10 min. The results obtained good removal efficiencies for the degradation of P4R in the real aqueous solutions introducing it as an efficient decolorization method for treatment of P4R polluted waters. [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]

This study reports, for the first time, on the assessment of a multistage sequential system composed of coagulation–flocculation with different electro-Fenton-based configurations, followed by neutralization (N), for the treatment of raw textile wastewater heavily contaminated with acid black 194 dye and other pollutants. Electrochemical peroxidation (ECP-N), electro-Fenton (EF-N) and peroxi-coagulation (PC-N) were tested at laboratory scale and compared in terms of their efficiency for the removal of organic matter and color, current efficiency and energetic parameter, operating cost and environmental sustainability using life cycle analysis conducted in large-scale virtual reactors. The three electro-Fenton-based systems complied with current environmental standards (color removal > 87%, COD < 400 mg/L, among others) requiring different electrolysis times: ECP-N (52 min) < PC-N (120 min) < EF-N (160 min); energy consumptions: ECP-N (2.27 kWh/m3) < PC-N (4.28 kWh/m3) < EF-N (33.2 kWh/m3); operational costs: ECP-N (2.63 USD/m3) < EF-N (6.65 USD/m3) < PC-N (6.98 USD/m3); among others. Electricity (for ECP-N and EF-N) and reagents (for ECP-N and PC-N) were found as main environmental hotspots. ECP-N presented the lowest carbon footprint of 10.3 kg CO2-Eq/FU (2-Eq/FU) < EF-N (38.0 kg CO2-Eq/FU), had lower incidence in all the impact categories analyzed (ReCiPe-2016 at midpoint level) and can be considered technically, economically and environmentally sustainable for large-scale applications. [ABSTRACT FROM AUTHOR]

Low-cost stainless-steel electrodes can activate hydrogen peroxide (H2O2) by converting it into a hydroxyl radical (•OH) and other reactive oxidants. At an applied potential of +0.020 V, the stainless-steel electrode produced •OH with a yield that was over an order of magnitude higher than that reported for other systems that employ iron oxides as catalysts under circumneutral pH conditions. Decreasing the applied potential at pH 8 and 9 enhanced the rate of H2O2 loss by shifting the process to a reaction mechanism that resulted in the formation of an Fe(IV) species. Significant metal leaching was only observed under acidic pH conditions (i.e., at pH

Electro-Fenton process could remove pollutant in in tannery industry wastewater. The objectives of this is used to know the effect of electro-Fenton on, ammonia (NH3), chromium (III) (Cr(III), total suspended solid (TSS), biological oxygen deman d (BOD), and chemical oxygen demand (COD) removal in tannery wastewater treatment. The voltage variation used to trigger the electro-Fenton reaction was 6V, 8V, and 10V. Observation time at 0, 30, 60, 90, and 120 mins was used to see changes in the sample. The results obtained are electro-Fenton method has an effective time of 30 mins to removal efficiency of 60.7%, 32.9%, 72.8%, 53.4%, and 53.4% for NH3, Cr(III), TSS, BOD, and COD respectively. Pollution from tannery effluent can be eliminated to a sufficient extent using the electro-Fenton technique.

This study deals with the elimination of methyl orange (MO) from an aqueous solution by utilizing the 3D electro-Fenton process in a batch reactor with an anode of porous graphite and a cathode of copper foam in the presence of granular activated carbon (GAC) as a third pole, besides, employing response surface methodology (RSM) in combination with Box-Behnk Design (BBD) for studying the effects of operational conditions such as current density (3- 8 mA/cm2), electrolysis time (10- 20 min), and the amount of GAC (1- 3 g) on the removal efficiency beside to their interaction. The model was veiled since the value of R2 was high (>0.98) and the current density had the greatest influence on the response. The best removal efficiency (MO Re%) at pH= 3 was 95.62% with an average energy consumption of 6.22 kWh/kg MO, which was achieved at maximal conditions of current density = 5.12 mA/cm2, mass of GAC = 3 g, and time = 20 min with small amounts of Fe2+ (0.124 mM), and Na2SO4 (0.02 M). Moreover, the present work investigated the effectiveness of 3D electro-Fenton assisted by ultrasound known as Sono-Electro-Fenton (SEF), by following a new strategy based on applying the minimum circumstances of EF and comparing its results with that of SEF under the same conditions. MO Re% for EFmin was 49.24% while SEF was 50.51%, which is considered an exiguous improvement. However, using copper foam as a working electrode in the 3D EF system for the degradation of MO was an excellent choice. Furthermore, the suggested approach is characterized by simplicity, speed, and efficiency with a high percentage of pollutant removal, in addition to being eco-friendly.

This study deals with the elimination of methyl orange (MO) from an aqueous solution by utilizing the 3D electroFenton process in a batch reactor with an anode of porous graphite and a cathode of copper foam in the presence of granular activated carbon (GAC) as a third pole, besides, employing response surface methodology (RSM) in combination with Box-Behnk Design (BBD) for studying the effects of operational conditions, such as current density (3–8 mA/cm² ), electrolysis time (10–20 min), and the amount of GAC (1–3 g) on the removal efficiency beside to their interaction. The model was veiled since the value of R² was high (>0.98) and the current density had the greatest influence on the response. The best removal efficiency (MO Re%) at pH = 3 was 95.62% with an average energy consumption of 6.22 kWh/kg MO, which was achieved under maximal conditions of current density = 5.12 mA/cm², mass of GAC = 3 g, and time = 20 min with small amounts of Fe2+ (0.124 mM), and Na2 SO4 (0.02 M). Moreover, the present work investigated the effectiveness of 3D electro-Fenton assisted by ultrasound known as Sono-ElectroFenton (SEF), by following a new strategy based on applying the minimum circumstances of EF and comparing its results with that of SEF under the same conditions. MO Re% for EFmin was 49.24% while SEF was 50.51%, which is considered an exiguous improvement. However, using copper foam as a working electrode in the 3D EF system for the degradation of MO was an excellent choice. Furthermore, the suggested approach is characterized by simplicity, speed, and efficiency with a high percentage of pollutant removal, in addition to being eco-friendly. [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 electro-Fenton oxidation process was used to treat organic pollutants in industrial wastewater as it is one of the most efficient advanced oxidation processes. The novel cell in this process consists of a prepared PbO2 electrode by electrodeposition on graphite substrate and carbon fiber modified with graphene as a cathode. X-ray diffraction, fluorescence, analysis system, atomic force microscopy, and scan electron microscopy were used to characterize the prepared anode and cathode. XRD patterns clearly show the characteristic reflection of the mixture of α - and β phases of PbO2 on graphite and carbon fiber, and AFM results for cathode and anode present that PbO2 on graphite substrate and graphene on carbon fiber surface are on a nanoscale. Contact angle measurement was determined for the carbon fiber cathode before and after modification. The anodic polarization curve showed a higher anodic current when utilizing the PbO2 anode than the graphite anode. Phenol in simulated wastewater was removed by electro-Fenton oxidation at 8 mA/cm² current density, 0.4 mM of ferrous ion concentration at 35 °C up to 6 h of electrolysis. Chemical oxygen demand for the treated solution was removed by 94.02% using the cell consisting of modified anode and cathode compared with 81.23% using modified anode and unmodified cathode and 79.87% when using unmodified anode and modified cathode. [ABSTRACT FROM AUTHOR]

Dairy wastewater (DW) contains a high concentration of organic and inorganic pollutants. In recent years, extensive research has been conducted to develop more efficient techniques for the treatment of DW. Electrochemical advanced oxidation processes (EAOPs) have gained significant attention among the various treatment approaches. EAOPs rely on electrochemical generation of hydroxyl radicals (•OH) which are considered highly potent oxidizing compounds for the degradation of pollutants in DW. In this paper, we provide an overview of the treatment of DW using various EAOPs, including anodic oxidation (AO), electro-Fenton (EF), photo electro-Fenton (PEF), and solar photo electro-Fenton (SPEF) processes, both individually and in combination with other techniques. Additionally, we discuss the reactor design and operating parameters employed in EAOPs. The variation in degradation efficiency is due to different oxidizing agents produced in specific approaches and their pollutant degradation abilities. In AO process, •OH radicals generated on electrode surfaces are influenced by electrode material and current density, while EF procedures use Fe2+ to create oxidizing agents both on electrodes and in the DW solution, with degradation mechanisms being affected by Fe2+, pH, and current density; additionally, PEF and SPEF approaches enhance oxidizing component production and pollutant degradation using ultraviolet (UV) light. Integration of EAOPs with other biological processes can enhance the pollutant removal efficiency of the treatment system. There is a scope of further research to exhibit the effectiveness of EAOPs for DW treatment in large scale implementation. [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]

Carbon xerogel spheres co-doped with nitrogen and eco-graphene were synthesized using a typical solvothermal method. The results indicate that the incorporation of eco-graphene enhances the electrochemical properties, such as the current density (JK) and the selectivity for the four transferred electrons (n). Additionally, nitrogen doping has a significant effect on the degradation efficiency, varying with the size of the carbon xerogel spheres, which could be attributed to the type of nitrogenous group doped in the carbon material. The degradation efficiency improved in the nanometric spheres (48.3% to 61.6%) but decreased in the micrometric-scale spheres (58.6% to 53.4%). This effect was attributed to the N-functional groups present in each sample, with N-CNS-5 exhibiting a higher percentage of graphitic nitrogen (35.7%) compared to N-CMS-5 (15.3%). These findings highlight the critical role of sphere size in determining the type of N-functional groups present in the sample. leading to enhanced degradation of pollutants as a result of the electro-Fenton process. [ABSTRACT FROM AUTHOR]

A batch-scale electro-Fenton (EF) process was performed using graphite anode and waste battery-based Fe -Mn -Zn/C electrocatalyst coated on low-cost graphite felt cathode. The effectiveness of the EF's performance was evident with around 83.9 + 4.1% removal of 20 mg/L of sodium-dodecyl sulfate surfactant (SDS) at an optimum current density (CD) of 5.0 mA/cm2, Na2SO4 of 0.05 M, initial pH of 7.2, and electrolysis time of 180 min. Moreover, nearly 1.78-fold more removal of SDS was achieved in EF than in the electro-oxidation process operated without any catalyst. The operating cost of 0.35 $ of per m3 per order was needed to treat SDS wastewater. The remediation of SDS follows pseudo-first-order kinetics with a rate constant of 0.0095 min−1. Additionally, 90.3 + 2.1% of SDS and 57 + 2.6% of total organic carbon (TOC) removal was attained during 240 min of treatment time in secondary treated real wastewater; hence, additional 60 min of treatment time is required for effectively treating real wastewater than synthetic wastewater. Thus, EF is effective with battery waste-derived magnetic catalyst for treating wastewater containing SDS, which can lead to achieving sustainable environmental goals. HIGHLIGHTS The current work demonstrates a waste-to-treat-waste approach.; Magnetic Fe–Mn–Zn/C catalyst derived from battery waste was used in electro-Fenton.; Efficacious degradation of surfactant was obtained with a battery waste catalyst.; The kinetics of removal obtained a pseudo-first-order kinetic model.; Lauric acid was formed during sodium dodecyl sulfate degradation.;

Abstract: This review provides a current opinion on the most recent works that have been published toward the application of electrochemical advance oxidation processes (EAOPs) for the degradation of pharmaceutical and personal care products (PPCPs) in water streams. Advances in the application of anodic oxidation (AO)- and electro-Fenton (EF)-based processes are reported, including operational conditions, electrode performance, and removal. Although AO- and EF-based processes can easily reach 100% removal of PPCPs, mineralization is desirable to avoid the generation of potential toxic byproducts. The following section exploring some techno-economic aspects of the application of EAOPs is based on electrode selection, operational costs as well as their use as cotreatments, and their synergistic effects. Finally, this short review ends with perspectives about the emerging topics that are faced by these technologies applied for the degradation of PPCPs in research and practice.

• 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]

Herein, a carbon felt (CF) cathode modified by the acidic oxidised carbon nanotubes (OCNTs) exhibited a high yield of the H2O2 generation in electro-Fenton. Rotating disk electrode (RDE) measurements showed that the selective generation of H2O2 occurred on the CF cathode coated by OCNTs (OCNTs/CF), which was attributed to the high amount of oxygen-containing functional groups in OCNTs. Moreover, the pollutant degradation efficiency could almost reach 100% within 60 min in electro-Fenton with OCNTs/CF as the cathode. Furthermore, the pollutant removal efficiency was kept constant after five consecutive cycles, indicating the high stability of OCNTs/CF cathode. Besides, the hydrophilicity of OCNTs/CF cathode was significantly enhanced owing to the abundant oxygen-contained functional groups on the surface of the OCNTs/CF cathode, which facilitated the mass transfer between the OCNTs/CF cathode and the reactants in the bulk solution. To reveal the possible mechanism in electro-Fenton equipped with the OCNTs/CF cathode, quenching experiments and electron paramagnetic resonance (EPR) investigations were further conducted. This work provided valuable insights into the fabrication of the non-metallic cathode with a high ability towards H2O2 generation in electro-Fenton for efficient pollutant removal. [ABSTRACT FROM AUTHOR]

This research explored the use of a granular activated carbon (GAC) column to treat dissolved organics in Combined Sewer Overflows (CSOs), a major river pollutant. The regeneration efficiency of spent GAC was assessed utilizing three distinct methods: biological denitrification, electro-Fenton oxidation, and Sono-Fenton oxidation. Among the six organics tested, sucrose and raw sewage demonstrated the most comparable adsorption characteristics. GAC adsorption factors are multifaceted, involving pore size, surface functional groups, and competing solution substances, rather than just organic matter hydrophobicity. The biological denitrification enabled the utilization of the adsorbed organic matter on spent GAC, consequently reducing the initial NO3-N concentration from 99 mg/L to 8 mg/L over a period of 48 hours. Electro-Fenton treatment revealed marginal performance differences between SUS-SUS and Ti/Pt-Ti/Pt; however, the latter proved superior in terms of electrode stability over prolonged use. A combined strategy employing ultrasound and Fenton treatment at a frequency of 40 kHz yielded marginally higher GAC regeneration efficiency (68.5%) as compared to that at 750 kHz (67.8%). Among all regeneration techniques applied in this investigation, the Sono-Fenton method showed the highest efficiency. [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]

Coal gasification technology is essential for realizing clean and efficient conversion of coal, as well as for reducing carbon emissions. However, coal gasification technology is accompanied by a large amount of coal gasification wastewater that is biodegradable. In this work, tourmaline was applied as a catalyst in electro-Fenton like process for treating coal gasification wastewater. The optimal applied parameters of coal gasification wastewater were investigated as follows: current density of 90 mA cm−2, tourmaline dosage of 8 g L−1, electrode gap of 1 cm, and temperature at 25 °C; the COD removal ratio reached 91.24% after 240-min treatment. In addition, the current density and tourmaline dosage were further optimized by response surface method. The result was about current density with 82.4 mA cm−2 and catalyst with 7.57 g L−1; the predicted COD removal efficiency was 86.91%. Under the optimal parameters the actual COD removal efficiency was 88.25% a little high than the predicted value. To explore the reusability of tourmaline as Fenton reaction catalyst, five cycles of experiments were carried out. The result demonstrated that tourmaline could be used as catalyst for treating coal gasification wastewater by electro-Fenton like process. [ABSTRACT FROM AUTHOR]

In this study, cobalt etched graphite felt electrodes were produced using a simple etching technique. It was used in combination with a solid polymer electrolyte (SPE) for the degradation of the target contaminant Orange II by Electro-Fenton (EF) technique in low conductivity water. In this method, 94% of Orange II in low conductivity water was removed in 90 min. The characterization analysis substantiates the hypothesis that the electrodes produced exhibit a three-dimensional porous structure, augmented defect concentration, and enhanced electron transfer capability. In addition, the potential reaction mechanism was inferred from the radical quenching experiments, and hydroxyl radicals (·OH) were deemed the main reactive substances. The combination of cobalt etched graphite felt electrodes with SPE demonstrates remarkable efficacy in the treatment of organic wastewater characterized by low electrical conductivity. [ABSTRACT FROM AUTHOR]

Wastewater containing reactive textile dyes constitutes a crucial environmental problem as they are permanent and dangerous. The electro-Fenton (EF) method is promising as an effective technique for degrading organic materials such as dyestuffs. In this study, the optimization of influential variables in removing reactive yellow 145 azo textile dye by EF was investigated using response surface methodology (RSM). Central composite design was used to study the combined effects of critical parameters such as voltage (2.5–12.5 V), H2O2 addition (0.1–1.3 mL), pH (1.75–4.75), electrode spacing (0.25–3.25 cm), and treatment time (25–85 min). The optimum values of the variables to ensure the highest dye removal efficiency (approx. 93%) with the lowest energy consumption (approx. 3.4 Wh/L) were approximately 9.4 V voltage, pH 3.7, 2.5 cm electrode spacing, 1 mL H2O2 addition, and a 40-min treatment time. ANOVA analysis of the predicted quadratic polynomial model showed a regression coefficient value of approximately 0.97 for both objective functions; this highlights the model's applicability for navigating the design space. Simultaneous optimization of process parameters using RSM was achieved with a few experiments. [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]

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]

A comparative study of the results obtained from using Fenton and electro-Fenton processes in textile wastewater treatment is presented. Global indicators, color, COD, TOC, and BOD5 were employed to investigate the treatments. Examination of the representative by-products gave new insights into Fenton. Even though the color removal was higher for classical Fenton (almost 100% color removal) than for electro-Fenton, the overall purification effect was not directly advantageous for Fenton. We found that electro-Fenton removed COD and TOC more efficiently. The biodegradability BI (BOD5/COD) parameter was investigated, where the textile wastewater was hardly biodegradable (BI was 0.12 ± 0.007). BI of Fenton was also low (0.044 ± 0.006). Electro-Fenton yielded a considerably more promising result, where BI was 0.83 ± 0.15, and proved more bio-friendly than classical Fenton. Additionally, electro-Fenton was more efficient in by-product removal, especially the naphthalic component, with 90% removal (while Fenton removed 50%). The by-products influenced the after-treatment toxicity assessment of V. fischeri. The EC50 values were below 2% and even lower for electro-Fenton. The results of the color matching parameters (DECMC) of re-dyeing were unacceptable using after-Fenton water at 8.66. DECMC results were between 1.01 and 2.71 after electro-Fenton treatment and had a recycling perspective.

The three-dimensional electrode-electro-Fenton method is a new advanced oxidation method that introduces three-dimensional electrode electrocatalytic technology on the basis of electro-Fenton，which has been widely used in water treatment. The activated brilliant orange X-GN wastewater was used as the treatment object，and the loaded three-dimensional electrode was prepared by excessive impregnation calcination method. The effects of pH，voltage，Fe2+ dosage and electrolyte concentration on the treatment effect were studied by experiments，and the experimental conditions were optimized by response surface method. The results showed that under the condition of pH 4.7，the supply voltage 20.39 V，the dosage of Na2SO4 2.13 g/L，and the dosage of Fe2+ 2.5 mmol/L，the removal rates of COD and chromaticity could reach 85.41% and 92.18%. The loaded three-dimensional electrode-electro-Fenton method has ideal treatment effect on the chromaticity and COD of reactive brilliant orange X-GN wastewater.

The aim of this study was to investigate the metronidazole (MNZ) degradation and real MNZ pharmaceutical wastewater treatment in the pulsed switching peroxi-coagulation (PSPC) process. Different pulsed switching frequencies and running times of H2O2 and Fe2+ productions were tested in the PSPC process. Results demonstrated that MNZ removal of 96.9 ± 1.2 % was realized in the PSPC process with a 200 mg/L MNZ and 0.1 M Na2SO4 solution within 80 min under a pulsed switching frequency of 6s: 1s and a current density of 20 mA/cm2 (H2O2) and 20 mA/cm2 (Fe2+). High MNZ removal could be attributed to efficient •OH production with the highest •OH concentration reached 321 ± 15 μM in the PSPC process. The hydroxyl and carboxyl groups of MNZ were sequentially oxidated by •OH and mineralized based on seven identified intermediates during the MNZ degradation. However, only 56.9 ± 6.7 % of COD was removed in the real MNZ wastewater treatment by the PSPC process within 90 min. A PSPC combined with electro-Fenton (EF) process was developed to enhance the COD removal in the MNZ wastewater. With MNZ wastewater as electrolytes, 3.3 ± 0.3 g/L of H2O2 was produced in a conventional EF reactor. The final COD removal reached 86–90 % using the mixture of effluent from the PSPC, the anode, and cathode chambers of the EF reactor, resulting in less than 80 mg/L COD in the effluent. Results from this study should provide a useful way to enhance real MNZ pharmaceutical wastewater treatment.

Hydrogen peroxide (H2O2) in situ electrosynthesis by O2 reduction reaction is a promising alternative to the conventional Fenton treatment of refractory wastewater. However, O2 mass transfer limitation, cathodic catalyst selectivity, and electron transfer in O2 reduction remain major engineering obstacles. Here, we have proposed a systematic solution for efficient H2O2 generation and its electro-Fenton (EF) application for refractory organic degradation based on the fabrication of a novel ZrO2/CMK-3/PTFE cathode, in which polytetrafluoroethylene (PTFE) acted as a hydrophobic modifier to strengthen the O2 mass transfer, ZrO2 was adopted as a hydrophilic modifier to enhance the electron transfer of O2 reduction, and mesoporous carbon CMK-3 was utilized as a catalyst substrate to provide catalytic active sites. Moreover, feasible mass transfer of O2 from the hydrophobic to the hydrophilic layer was designed to increase the contact between O2 and the reaction interface. The H2O2 yield of the ZrO2/CMK-3/PTFE cathode was significantly improved by approximately 7.56 times compared to that of the conventional gas diffusion cathode under the same conditions. The H2O2 generation rate and Faraday efficiency reached 125.98 mg·cm−2·h−1 (normalized to 5674.04 mmol·g−1·h−1 by catalyst loading) and 78.24% at −1.3 V versus standard hydrogen electrode (current density of −252 mA·cm−2), respectively. The high H2O2 yield ensured that sufficient OḢ was produced for excellent EF performance, resulting in a degradation efficiency of over 96% for refractory organics. This study offers a novel engineering solution for the efficient treatment of refractory wastewater using EF technology based on in situ high-yield H2O2 electrosynthesis.

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.

In this study, an electro-Fenton-like method in the presence of iron particles was used for degradation of toxic thiophene pollutant from aqueous samples with performance >99%. In an electrolytic reactor, the effect of current density, H2O2 dosage, and pH of the sample on the treatment efficiency was investigated and optimized using the response surface method in the experimental design methodology. The conditions were optimized in current density of 20 mA/cm2, H2O2 dosage 500 ppm and pH = 3.0. In this process, a laser pulse ablation was used to produce iron nanoparticles in the electro-Fenton reactor to decrease the treatment time. Also, two bimetallic iron–copper and iron–zinc were used to investigate the synergistic effect of bimetallic catalyst on degradation efficiency of thiophene. The removal of thiophene nearly 100% can be provided in the presence Fe0.5/Cu0.5, Fe0.5/Zn0.5 and Fe alone in 10, 15 and 20 min, respectively. Also, the effect of hydroxyl scavenger and the consumption of catalysts were studied in the proposed procedure. Techniques of gas chromatography-flame ionization detector (GC-FID), gas chromatography-sulphur chemiluminescence detector (GC-SCD) and total sulphur analyser were used to follow thiophene degradation. A thiophene petrochemical wastewater was treated by the proposed method, and the results showed a significant reduction in amounts of chemical oxygen demand (COD) and biochemical oxygen demand (BOD). [ABSTRACT FROM AUTHOR]

This work focuses on applying a combined process combining electro-Fenton (EF) pretreatment with biological degradation to mineralize the antiviral Ribavirin in an efficient, economical and ecological manner. First, the main experimental parameters affecting the efficiency of the electro-Fenton process, namely applied current intensity, Fe(II) catalyst concentration and initial Ribavirin concentration were evaluated and optimized. Indeed, the mineralization rate reaches maximum residual values of 99% after 4 hours of electrolysis applying a current of 200 mA. This mineralization is accompanied by an increase in biodegradability, evaluated from the BOD5/COD ratio, which goes from 0.04 at the beginning of treatment (1 h) to 0.45 after 2 hours of electrolysis, demonstrating the feasibility of a biological treatment. In addition, the energy efficiency decreased when the treatment time was extended due to the limitation of mass transport. Thus, the feasibility of coupling electro-Fenton and biological treatment has been successfully demonstrated on a laboratory-scale was, achieving a 96.66% removal rate by the Bio-EF process. A Box-Behnken design based on response surface methodology was applied to develop a model for predicting Rib removal rate. The interaction of factors such as Rib concentration (X1), catalyst concentration (X2) and electrolysis time (X3) was analyzed to identify optimal operating conditions. The model results obtained are statistically significant with an R2 of 0.99, indicating that the proposed model is significant and relevant. In addition, the iso-response curves obtained enabled us to determine the optimal experimental conditions required for effective mineralization of the targeted antiviral. [ABSTRACT FROM AUTHOR]

The dairy industry is among the most contaminated of the food industries. Dairy industry wastewater contains a high organic load and chemical oxygen demand (COD). In recent years, due to the development of the dairy industry, the administration of dairy effluents has become the main problem since dairy effluents can be a dangerous and significant threat, especially to the aqueous environment. Therefore, there is an important need to improve the management and remediation of dairy effluents in order to ensure the economic viability of this major agricultural industry and to decrease environmental problems. Several works focused on the remediation of dairy wastewater. In this study, the effect of the electro-Fenton process on COD and turbidity removal from dairy wastewater was studied. The electro-Fenton process was optimized for four independent variables (pH, reaction time, volume of H2O2, and H2O2/Fe2+ (the molar ratio)). Moreover, the response surface methodology was utilized to design experiments and determine optimum operating conditions. Under optimal conditions (pH = 5.95, reaction time = 60 min, volume of H2O2 = 1.5 ml and the molar ratio of H2O2/Fe2+ = 1.8), the removal efficiency of COD was 95.8%. Also under optimal conditions (pH = 6.37, reaction time = 60 min, volume of H2O2 = 1.5 ml and the molar ratio of H2O2/Fe2+ = 2.09), the removal efficiency of turbidity was 97.2%. [ABSTRACT FROM AUTHOR]

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Pharmaceutical wastewater containing contaminants like aspirin, ofloxacin, and amoxicillin are emerging as a worldwide issue due to its significant effects on the ecosystem and public health. In this study, wastewater containing aspirin was treated by using Mn3O4 etched graphite felt (EGF) as a cathode in an MFC-powered electro-Fenton system. The electrochemical characterization of etched electrodes revealed that etching at 400 °C for 1.5 h showed the highest electrochemical activity and rapid electron transfer with a peak current of − 0.058A. The physicochemical characterization exhibited a porous morphology with high defect concentration (ID/IG ratio of 1.56) and increased specific surface area and superhydrophilicity, proving its ability to regenerate Fe2+ on the cathodic surface and promote H2O2 generation. MFC exhibits a maximum power density of 0.053 W/m2 and a current density of 0.516 A/ m 2 . Under optimized conditions of 0.7 mM iron concentration, pH 3, and 100 Ω resistance, the MFC-powered electro-Fenton system showed a maximum of 95.85% aspirin degradation in 30 h with a highest H2O2 generation of 11.84 mg/l. The results highlight the potential of EGF electrodes as efficient cathodes in MFC-powered electro-Fenton systems and suggest that this technology can be opted as an energy-saving system for degrading pharmaceuticals such as aspirin from wastewater. [ABSTRACT FROM AUTHOR]

The electro-Fenton process is based on the generation of hydroxyl radicals (OH•) from hydroxide peroxide (H2O2) generated in situ by an oxygen reduction reaction (ORR). Catalysts based on carbon gels have aroused the interest of researchers as ORR catalysts due to their textural, chemical and even electrical properties. In this work, we synthesized metal-free electrocatalysts based on carbon gels doped with graphene oxide, which were conformed to a working electrode. The catalysts were prepared from organic-gel-based inks using painted (brush) and screen-printed methods free of binders. These new methods of electrode preparation were compared with the conventional pasted method on graphite supports using a binder. All these materials were tested for the electro-Fenton degradation of amoxicillin using a homemade magnetite coated with carbon (Fe3O4/C) as a Fenton catalyst. All catalysts showed very good behavior, but the one prepared by ink painting (brush) was the best one. The degradation of amoxicillin was close to 90% under optimal conditions ([Fe3O4/C] = 100 mg L−1, −0.55 V) with the catalyst prepared using the painted method with a brush, which had 14.59 mA cm−2 as JK and a H2O2 electrogeneration close to 100% at the optimal voltage. These results show that carbon-gel-based electrocatalysts are not only very good at this type of application but can be adhered to graphite free of binders, thus enhancing all their catalytic properties. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2), as a versatile and environmentally friendly oxidant, has drawn increasing attention in energy and environmental applications. Aiming at boosting the in situ electrocatalytic H2O2 production and activation toward water purification, we developed a two-dimensional (2D) CuO nanosheet-modified activated carbon fiber (CuO NSs/ACF) bifunctional free-standing hybrid composite electrode. The introduction of 2D CuO NSs well modulated the electronic structure and surface wettability of hybrid electrodes, promoting the two-electron oxygen reduction reaction (ORR) for H2O2 generation and the following CuO-catalyzed Fenton efficiency. Taking bisphenol A (BPA) as the target pollutant, the BPA degradation and TOC removal could reach 99.45 and 74.04%, respectively, after 30 min electrolysis. We identified the reactive oxygen species (•OH and •O2–) produced in the CuO NSs/ACF system and further discussed the tuning mechanisms. This work provided a promising 2D material modification strategy for boosting in situ electrochemical H2O2 production and electro-Fenton activity and facilitating its application for water purification. [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]

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 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]