electro-Fenton Reaction Research Articles

The Degradation of Rhodamine B by an Electro-Fenton Reactor Constructed with Gas Diffusion Electrode and Heterogeneous CuFeO@C Particles

Compared with conventional Fenton processes, the electro-Fenton process consumes fewer chemicals and produces less sludge, as it can generate the required Fenton’s reagents in situ. In this work, an electro-Fenton reactor was constructed to treat synthetic rhodamine B (Rh B) wastewater, in which a gas diffusion electrode (GDE) was used as a cathode to produce H2O2, and heterogeneous CuFeO@C particles were used to generate Fe2+ in situ. The results indicated that the gas diffusion electrode made of elements N-S-B and r-graphene oxide (NSB-r-GO) composites produced more H2O2 than the one made from r-graphene oxide (r-GO), under the conditions of 0.1 mol ·L−1 Na2SO4 electrolyte, 10 mA·cm−2 current density, and 1.0 L·min−1 O2 flow rate, with the accumulated H2O2 production reaching 105.43 mg·L−1. Additionally, different iron morphologies, including octahedral Fe (II), octahedral Fe (III), and tetrahedral Fe (III), were found in the calcined CuFeO@C particles, approximately 1.0 mg·L−1 of iron ions dissolved in the electrolyte was detected, which worked simultaneously as conductive electrodes in a conceptual three-dimensional electrochemical reactor consisting of a gas diffusion electrode cathode, Ti/RuSn anode, and CuFeO@C particle electrodes. No external Fenton reagents were necessary.

Treatment of textile dyes with steel flakes via Fenton and Electro-Fenton processes: An experimental analysis

The textile production process is well recognised as one of the most water-intensive industries, with an estimated daily water consumption of several thousand cubic metres. The main objective of the study is to remove the colour and COD of three reactive dyes namely reactive blue, reactive yellow and reactive black by Fenton and Electro Fenton Process. In this research paper, new novel catalyst steel flakes have been employed as part of the Fenton and Electro-Fenton process, replacing the conventional Fenton and Electro-Fenton catalyst. Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Analysis (EDAX), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Thermo Gravimetric Analysis (TGA) was done to characterize the steel flakes. The pH, dye concentration, FeSO4 dosage and H2O2 dosage were studied. The maximum colour and Chemical Oxygen Demand (COD) removal in Fenton process was 98.47 % and 74 % respectively. In Electro Fenton Oxidation the maximum colour and COD removal was 99.65 % and 78 % respectively. The best colour and COD removal was observed by Fenton and Electro Fenton oxidation with optimum Fenton molar ratio of 50:1 and pH 3 in all three dyes. In the laboratory-scale feasibility tests on the Electro-Fenton process, the highest colour removal effectiveness was observed at catalyst dosages of 1 g/L, 132 mM H2O2, and pH 3. The novel modified heterogeneous Electro-Fenton approach presents a distinct cost-effectiveness benefit in comparison to both the conventional Electro-Fenton reaction and the Electro-Fenton reaction employing alternative iron sources.

Using flow-through reactor to enhance ferric ions electrochemical regeneration in electro-fenton for wastewater treatment

Electrochemical regeneration of ferric ions catches more and more attention since it could decrease iron sludge to avoid the sludge problem while it could simultaneously obtain similar robust removal efficiency to refractory organic contaminants in wastewater treatment as the normal Fenton agent method. However, the electrochemical regeneration of ferric ions in aqueous solution was very slow. In this paper, the mass transfer limit of ferric ions in electro-Fenton reaction was evaluated. Koutecky-Levich equation reveals an extremely low diffusion coefficient (D0) value of ferric ions since its complex coordination of [Fe(HO)x(H2O)6-x]3-x. The D0 value was only 2.70 × 10−6 cm2·s−1. Flow-through reactor was therefore introduced in which the ferric ions was designed to penetrate through the 73.1 μm porous holes in the graphite fiber electrode. The μm-scaled confinement of ferric ions diffusion inside the holes was proved to successfully enhance the reduction current of ferric ions by more than 200 % since the diffusion distance of the ferric ions was significantly decreased in the flow-through reactor. However, besides the benefit of the flow-through reactor, the ferric ions reduction electro-Fenton (FeRR electro-Fenton) in flow-through still faces both the pH limit and H2O2 decomposition problems. Hydrogen evolution reaction (HER) could also cause the decrease of pH which exceeded the optimal pH window for Fenton and therefore destroyed the electro-Fenton reaction consequently although the electrochemical reaction of FeRR was 770 mV prior to HER reaction. The regeneration of Fe (II) process simultaneous destruction of H2O2 since H2O2 e-reduction was 120 mV prior to FeRR reaction, which resulted in only very low H2O2 concentration suitable for FeRR electro-Fenton. Even using stepwise addition of H2O2 in electro-Fenton, the decomposition of H2O2 still could not be avoided. Although the decomposition of H2O2 quite limited the application of FeRR electro-Fenton in real application, FeRR electro-Fenton still supports the enhancement removal efficiency of the refractory organic contaminants under low organic contaminants application.

Advanced electrochemical strategies for simultaneous removal of Microcystis aeruginosa and microcystin-LR: On-demand optimization and mechanistic insights

The frequent occurrence of harmful cyanobacterial blooms and toxins poses significant threats to aquatic life and drinking water safety. This work reports the removal mechanisms of M. aeruginosa and microcystin-LR (MC-LR) using the Pt-Graphite felt (GF) electrochemical system, which builds upon prior research to investigate diverse processes driven by distinct mechanisms within a single reactor, primarily by pH regulation. Factors affecting removal were assessed through single-factor trials and Box-Behnken design, identifying optimal conditions for successful algae removal, finally a 96% removal efficiency of algae cells and an 83% elimination efficiency of MC-LR within a 60-minute timeframe. Particularly at non-optimal pH 7 conditions, the Pt-GF system showcases synergistic effects, enhancing electro-flocculation and weakening electro-Fenton reactions. Conversely, at an optimal pH of 3, the electro-Fenton process is favorably enhanced, leading to improved removal efficiency through escalated reactive oxygen species generation. Additionally, the system exhibits consistent repeatability in its performance. Notably, its effectiveness is substantiated across varying nitrogen and phosphorus levels and in simulated water samples containing multiple algal species. In essence, this subtly adaptable reactor tuning integrates electro-Fenton, electro-flocculation, electro-adsorption, and electrochemical direct oxidation effects for the first time, potentially providing a more effective and manageable solution for addressing harmful algae in water.

Structural Modulation of Covalent Organic Frameworks for Efficient Hydrogen Peroxide Electrocatalysis.

The electrochemical production of hydrogen peroxide (H2O2) using metal-free catalysts has emerged as a viable and sustainable alternative to the conventional anthraquinone process. However, the precise architectural design of these electrocatalysts poses a significant challenge, requiring intricate structural engineering to optimize electron transfer during the oxygen reduction reaction (ORR). Herein, we introduce a novel design of covalent organic frameworks (COFs) that effectively shift the ORR from a four-electron to a more advantageous two-electron pathway. Notably, the JUC-660 COF, with strategically charge-modified benzyl moieties, achieved a continuous high H2O2 yield of over 1200 mmol g-1 h-1 for an impressive duration of over 85 hours in a flow cell setting, marking it as one of the most efficient metal-free and non-pyrolyzed H2O2 electrocatalysts reported to date. Theoretical computations alongside in situ infrared spectroscopy indicate that JUC-660 markedly diminishes the adsorption of the OOH* intermediate, thereby steering the ORR towards the desired pathway. Furthermore, the versatility of JUC-660 was demonstrated through its application in the electro-Fenton reaction, where it efficiently and rapidly removed aqueous contaminants. This work delineates a pioneering approach to altering the ORR pathway, ultimately paving the way for the development of highly effective metal-free H2O2 electrocatalysts.

Coupling Electro-Fenton and Electrocoagulation of Aluminum-Air Batteries for Enhanced Tetracycline Degradation: Improving Hydrogen Peroxide and Power Generation.

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.

The investigation of heavy metal-contaminated dredged sediments by electro-Fenton: Oxidizing organically bound forms of metals with simultaneous efficient dewatering

Based on the principle of electro-Fenton (EF) reaction, this investigation was experimented to treat copper (Cu) and lead (Pb), which are lower mobile in dredged sediment in a self-made EF reactor, and simultaneously dewater it. The results of the study showed that when Fe2+ concentration was 1 mM, the initial current density was 10.4 mA/cm2, and the initial pH was neutral, after 24 h, the conversion of the stable form to the activated state of Cu and Pb were 24.77 % and 68.42 %, respectively. Further, the water content of the dredged sediment was significantly reduced from the initial 58–26 % after the EF. The mechanism experiment confirmed that ·OH and SO4·- were the main factors for converting Cu and Pb forms, destroying the EPS structure in the dredged sediment and decomposing its main components, improving the dewatering property of the dredged sediment. In addition, EF treatment did not decrease microbial diversity in dredged sediments, and Flavobacterium and Bacillus, which are beneficial for agricultural production, became featured taxa after EF. This study provided a new perspective that transforms Cu and Pb into a more easily removable form with simultaneous efficient dewatering, which is more conducive to subsequent conventional treatment of the dredged sediment.

In situ Production of Hydroxyl Radicals via Three‐Electron Oxygen Reduction: Opportunities for Water Treatment

The electro‐Fenton (EF) process is an advanced oxidation technology with significant potential; however, it is limited by two steps: generation and activation of H2O2. In contrast to the production of H2O2 via the electrochemical two‐electron oxygen reduction reaction (ORR), the electrochemical three‐electron (3e‐) ORR can directly activate molecular oxygen to yield the hydroxyl radical (·OH), thus breaking through the conceptual and operational limitations of the traditional EF reaction. Therefore, the 3e‐ ORR is a vital process for efficiently producing ·OH in situ, thus charting a new path toward the development of green water‐treatment technologies. This review summarizes the characteristics and mechanisms of the 3e‐ ORR, focusing on the basic principles and latest progress in the in situ generation and efficient utilization of ·OH through the modulation of the reaction pathway, shedding light on the rational design of 3e‐ ORR catalysts, mechanistic exploration, and practical applications for water treatment. Finally, the future developments and challenges of efficient, stable, and large‐scale utilization of ·OH are discussed based on achieving optimal 3e‐ ORR regulation and the potential to combine it with other technologies.

In Situ Production of Hydroxyl Radicals via Three-Electron Oxygen Reduction: Opportunities for Water Treatment.

The electro-Fenton (EF) process is an advanced oxidation technology with significant potential; however, it is limited by two steps: generation and activation of H2O2. In contrast to the production of H2O2 via the electrochemical two-electron oxygen reduction reaction (ORR), the electrochemical three-electron (3e-) ORR can directly activate molecular oxygen to yield the hydroxyl radical (⋅OH), thus breaking through the conceptual and operational limitations of the traditional EF reaction. Therefore, the 3e- ORR is a vital process for efficiently producing ⋅OH in situ, thus charting a new path toward the development of green water-treatment technologies. This review summarizes the characteristics and mechanisms of the 3e- ORR, focusing on the basic principles and latest progress in the in situ generation and efficient utilization of ⋅OH through the modulation of the reaction pathway, shedding light on the rational design of 3e- ORR catalysts, mechanistic exploration, and practical applications for water treatment. Finally, the future developments and challenges of efficient, stable, and large-scale utilization of ⋅OH are discussed based on achieving optimal 3e- ORR regulation and the potential to combine it with other technologies.

Efficient bioelectro-Fenton degradation of styrene using Fe/Mn modified bimetallic catalysts as microbial fuel cell cathodes

Microbial fuel cells (MFCs) can generate electricity to drive electro-Fenton (EF) reactions for contaminant degradation. The oxygen reduction ability, catalytic ability, electron transfer efficiency, and styrene degradation efficiency of the catalysts were evaluated by loading iron and manganese ions on graphite fiber (GF) as bimetallic catalysts on the cathode of MFC/EF. The surface-loaded Fe–Mn@GF cathode had the highest reduction peak current density (−136.64 mA/cm2), which was 1.99 times that of the Fe@GF (−68.62 mA/cm2) cathode and 16.64 times that of the GF (−8.21 mA/cm2) cathode. Polymorphic crystals of Fe2O3 and MnO2 were observed in the Fe–Mn@GF-loaded cathode, resulting in many active sites on the surface of the cathode to enhance the catalytic ability of the material. The maximum power density (469.71 mW/m2) and minimum total internal resistance (189.63 Ω) of Fe–Mn@GF as the MFC cathode demonstrated that the Mn-doped cathode has superior electrical conductivity and electron transfer rate, thus significantly decreasing the electron transfer resistance. The styrene removal efficiency of MFC/EF using Fe–Mn@GF in a three-cycle run was maintained at over 90.31 %−98.14 %. The bimetallic catalyst effectively promoted hydrogen peroxide (H2O2) generation, demonstrating that the Fe–Mn@GF system could stably produce ·OH for styrene degradation, and that MFC/EF with Fe–Mn@GF had almost no remaining biotoxicity after the first run. The most novel aspect of this study is the successful application of the MFC/EF system for styrene removal, providing a new approach for treating organic pollutants. Establishing this technology has important application value for improving water quality and environmental protection.

Fe-Ce based metal-organic framework as a novel heterogeneous catalyst accelerating redox cycle for efficient degradation of sulfamethoxazole in wide pH ranges

The electro-Fenton (EF) technology holds immense potential for wastewater treatment. However, there persist certain factors that affect its degradation efficiency, such as the restricted pH range, production of iron sludge and sluggish conversion rate between Fe2+ and Fe3+. Herein, 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) was introduced as the organic ligand to synthesize a series of efficient iron-based MOF catalysts (FexCe1-HHTP (x = 1, 2, 3, 4)) with different molar ratios for sulfamethoxazole (SMX) degradation in heterogeneous EF system. HHTP with electron-rich functional groups is beneficial to enhance performance of oxygen evolution reaction. Among these catalysts, Fe3Ce1-HHTP catalyst achieved 97.3 % degradation efficiency in 30 min and mineralization rate was 89.7 % at 1 h. The introduction of Ce promoted the transition of Fe3+ and Fe2+ in heterogeneous EF reaction. The synergistic effects between Fe3+/Fe2+ and Ce4+/Ce3+ further catalyzed the generation of hydroxyl radicals and it was proved as the main active species. The heterogeneous catalyst showed good performance in wide pH range, good stability, and high degradation efficiency to other pollutants. Three possible SMX degradation routes are suggested on basis of intermediates detected by mass spectrum analysis and theoretical calculations. The toxicity of these intermediates was assessed using Toxicity Estimation Software Tool (T.E.S.T.). This work provides valuable guidance for the design of highly efficient and stable heterogeneous EF catalyst for antibiotic degradation and expand the application potential in wastewater treatment of organic pollutants.

Enhanced hydrogen peroxide electrosynthesis and prolonged lifespan by preparing gas diffusion electrode via electrodeposition of CB on Ni foam

In-situ hydrogen peroxide (H2O2) production is pivotal for the effective implementation of the electro-Fenton reaction. However, challenges such as low H2O2 yields and a short electrode lifespan have hindered its application. This study introduced a novel gas diffusion electrode (GDE), the CB(E)-Ni foam(GDE), fabricated through a combination of carbon black (CB) electrodeposition and polytetrafluoroethylene (PTFE) impregnation techniques. Comprehensive physicochemical characterizations and electrochemical evaluations indicated that CB was more uniformly dispersed across the Ni foam, enhancing its electrochemical activity. When employed as a cathode, the CB(E)-Ni foam(GDE) demonstrated superior two-electron oxygen reduction reaction (2e− ORR) capabilities, marked by increased oxygen utilization and reduced energy demands, achieving a remarkable H2O2 concentration of 897.73 mg/L after 120 min. This performance significantly outpaces that of traditional GDEs. The unique structure of the CB(E)-Ni foam(GDE) not only prolonged electrode life by preventing rapid deactivation but also boosted H2O2 production and oxygen efficiency by 31.78% and 31.79%, respectively, when compared to a standard non-GDE configuration. In practical applications, the CB(E)-Ni foam(GDE) demonstrated utility by facilitating an 84.1% degradation rate of fulvic acid over 120 min within a homogeneous electro-Fenton system, highlighting its potential for environmental remediation.

Hemp-ball-like structured Fe3O4-hollow carbon sphere nanozymes functionalized carbon fiber cathode for efficient flow-through electro-Fenton

Electro-Fenton (EF) technology has been recognized as a highly promising electrochemical advanced oxidation process. Promoting effective contact between active species and contaminant is crucial in electrocatalysis. Herein, we had innovatively designed a unique nanozymes in the form of hemp-ball-like structures, consist of the uniform growth of Fe3O4 nanoparticles on nitrogen-doped nano hollow carbon spheres (NHCS). This catalyst was employed in a flow-through EF system with carbon felt (CF) filters serving as the work electrode. The active sites were fully exposed through the ultradispersed Fe3O4 nanoparticles, and the NHCS facilitated efficient cycling of Fe3+/Fe2+. The results showed that the generation capacity of hydroxyl radicals (·OH) was enhanced, and the oxidation flux reached 370.080 mg h−1m−2 with low energy consumption. The superiority of the hollow carrier was proved by the degradation results and COMSOL calculation for various carbon carriers. Moreover, the active catalyst exhibited adaptability in complex water matrices. This study offers a new perspective to synergize nanomaterials, EF reactions and flow-type systems.

Oxygen vacancy-induced nonradical degradation of nitroso-containing organics in Fe3O4@N[sbnd]C electro-Fenton reaction at a wide pH range

In this work, Fe3O4-anchored nitrogen-doped carbon catalyst (Fe3O4@N–C) with abundant oxygen vacancies (Vo) and mesoporous structure was successfully synthesized for electro-Fenton (EF) catalytic process. The catalyst demonstrated impressive degradation efficiency towards nitroso-containing organics due to the superior electronic transfer of N–C skeleton and Vo, making it easier for the electron-deficient –NO2 groups to adsorb on the catalyst surface and oxidize rapidly. Typically, the degradation efficiency of p-nitrophenol (PNP) reached 95.6 % in natural pH. Notably, the catalyst exhibited excellent performance over a wide pH range (3 ∼ 11), and has strong anti-interference performance against anions and natural organic matter in water matrix. Mechanism analysis indicated that Vo could promote the formation of highly active electron-rich Fe(II) species, and promote the activation of H2O2 and O2 as additional active sites, thus, a large amount of ·OH and O2·- would be produced and then quickly converted into 1O2. As a result, 1O2 is the main reactive species for PNP degradation in Fe3O4@N–C electro-Fenton reaction. The results will provide insights into the design of high-performance catalysts for the selective oxidation of organic pollutants in wastewater.

3D-TNAs/N-TiO2 photoanode assisted heterogeneous electro-Fenton with a novel Fe-MOFs@CF cathode for efficient synergetic oxidation of organic contaminants

Photoelectro-catalysis (PEC) and heterogeneous electro-Fenton (HEF) reactions are two frontier research fields for real effluent treatments. In the present work, a synergetic system with integration of both PEC and HEF has been developed for pollutant removal. PEC process with lower external bias results in the efficient separation of photogenerated hole and electrons, which can also modulate the HEF catalytic performance at the counter electrode, and in other cases the active HEF reaction can in turn affect the intrinsic activity of PEC. In this system, three dimensional TiO2 nanotube arrays coupled with nitrogen doped TiO2 nanoparticles (3D-TNAs/N-TiO2) was prepared as photoanode for solar light-driven PEC process while NH2-MIL-101 loaded on carbon felt (Fe-MOFs@CF) have been used as the cathode for HEF reaction. The performances of the synergetic system showed much higher degradation efficiency, which were evaluated by degrading typical organic containments in water (with the best of∼95 % in 5 min with 2*3 cm2 electrode area). The reaction rate in the coupling system were ∼7.25 and 1.18 times higher than single PEC or HEF with a wide pH applied range, well recycled and good stability for further application in water purification.

A novel bifunctional particle electrode with abundant Fe/Fe3C and Fe-N-C sites to enhance the performance of electro-Fenton in degrading organic pollutant

Electro-Fenton (EF) technology emerges as a promising approach to address the treatment of persistent organic pollutants. Nevertheless, its practical implementation often comes with certain drawbacks, like the low H2O2 activation efficiency, poor pH adaptability, and difficult recycling of the catalysts. To this end, we introduced highly active Fe-N-C sites onto the surface of nitrogen-doped graphene, improved the chemical environment of its central Fe atoms with Fe/Fe3C nanoparticles, effectively regulated the multi-electron oxygen reduction process of the catalyst in the electrochemical reaction, and realized the efficient production and activation of H2O2 in the electro-Fenton process. The synthesized Fe/Fe3C@FeNG-1000 achieved efficient removal of refractory organic pollutants in neutral conditions. The rate constant of degradation for tetracycline hydrochloride (TC) in the electro-Fenton reaction system at pH 7 was recorded as 0.1011 min−1. Additionally, a removal rate of 67.4% for total organic carbon (TOC) was achieved in just 120 min. The treatment of actual wastewater also showed excellent performance, with an average specific energy consumption of 6.16 kWh kg−1 COD−1. Fe/Fe3C@FeNG-1000 can still achieve more than 90% degradation efficiency after 5 consecutive cycles of the experiment, showing excellent stability, and the catalyst can be conveniently retrieved via magnetic methods following the reaction. The results show that the Fe/Fe3C@FeNG-1000-EF system has a wide range of pH applicability, long-term stability and good recyclability, has a good application value in practical wastewater treatment.

TCE degradation of modified graphite felt cathode in a flow-through electro-Fenton system and its H2O2 production ability in a real contaminated field

A modified graphite felt (MGF) was prepared with carbon black (CB) and polytetrafluoron (PTFE) for cathodic electrochemical H2O2 production, which was used in a flow-through cathodic electro-Fenton reactor to degrade chlorinated hydrocarbons. Cathode electrode was floating on aqueous surface and 369.1 mg/L H2O2 could be produced after 1 h 150 mA power applied without O2 aeration. The main O2 source for H2O2 production was confirmed from air with this floating position. In a 2.0 L flow-through cathodic electro-Fenton system, 95.97 % degradation efficiency for 5.0 mg/L trichloroethylene (TCE) was achieved in 90 min with 13.4 mL/min influent rate. Reducing the reactor volume to 0.14 L, 5.0 mg/L TCE could be degraded completely in 10 min with continuous 4 L influent. The mixed chlorinated hydrocarbons (TCE, cis-1,1-dichloroethylene, 1,2-dichloroethane, and dichloromethane) were also rapidly degraded in 20 min. The flow-through cathodic electro-Fenton reactor presented excellent degradation ability for chlorinated hydrocarbons with a smaller volume. In the simulated sand tank system, after continuously operated 27 days, H2O2 concentration in electrode well was still remained at 80 mg/L. In the contaminated field in Tianjin, China, H2O2 yield of MGF in groundwater could keep at about 60 mg/L after 220 min operating.

Reduced sulfur accelerates Fe(III)/Fe(II) recycling in FeS2 surface for enhanced electro-Fenton reaction

FeS2 is well-known for its role in redox reactions. However, the mechanism within heterogeneous electron-Fenton (Hetero-EF) systems remains unclear. In this study, a novel FeS2 based three-dimensional system (GF/Cu–FeS2) with self-generation of H2O2 was investigated for Hetero-EF degradation of sulfamethazine (SMZ). The results revealed that SMZ could be completely removed in 1.5 h, accompanying with the mineralization efficiency of 96% within 4 h. This system performed excellent stability, evidenced by consistently eliminated 100% of SMZ within 2 h over 4 cycles. The generated Reactive Oxygen Species (ROS) of •OH and •O2− in every degradation cycle were quantitatively measured to confirm the stability of the GF/Cu–FeS2 system. Additionally, the redox reaction mechanism on the surface of FeS2 was thoroughly analyzed in detail. The accelerated reduction of Fe(III) to Fe(II), triggered by S22− on the surface of FeS2, promoted the iron cycling, thereby quickening the Fenton process. Density Functional Theory (DFT) results illustrated the process of S22− to be oxidized to in detail. Therefore, this work provides deeper insight into the mechanistic role of S22− in FeS2 for environmental remediation.

Investigation of cluster magnetorheological electro-Fenton composite polishing process for single-crystal GaN wafer based on BBD experimental method

A cluster magnetorheological (MR) electro-Fenton composite polishing technique was proposed in this work, which can realize high efficiency, ultra-smooth and damage-free of GaN wafer by the synergistic effect of electro-Fenton reaction and flexible mechanical removal of MR polishing. The key parameters of electro-Fenton were optimized through methyl orange degradation experiments based on BBD experimental method. The results showed that the decolorization rate had a strong dependence on H2O2 concentration, Fe–C concentration and pH value, where the decolorization rate had the maximum value when the H2O2 concentration of 5 wt%, Fe–C concentration of 3 wt% and pH value of 3. Compared with the Fenton reaction, the decolorization and REDOX potential of methyl orange solution were significantly improved in the electro-Fenton reaction. Furthermore, the process parameters of the cluster MR electro-Fenton composite polishing were optimized to obtain the best polishing result, which was realized under the conditions of 3 wt% diamond (grain size: 0.5 µm), a polishing gap of 0.9 mm and a polishing time of 60 min. The novel method achieved a material removal rate of 10.79 μm h−1, which was much higher than that of the conventional technique. In addition, an ultra-smooth and damage-free surface with a roughness of 1.29 nm Ra was obtained.

High-entropy selenide catalyst for degradation of organic pollutants

In this study, pollution from sewage was addressed using a novel high-entropy material to decompose organic pollutants containing azo groups. Se_(AlCrCuFeNi) (Se_HEC) nanomaterials were employed as an active catalyst to restore organic pollution in aqueous solutions by using the electro-Fenton technique. The efficacy of Se_HEC catalysts in degrading pollutants during the electro-Fenton reaction and the potential of functionalized high-entropy materials to decompose pollutants were investigated. The Se_HEC material was synthesized through rapid calcination followed by selenization. This Se_HEC cathode demonstrated a remarkable removal efficiency of 98% for methyl orange in aqueous solutions and high stability in an acidic environment with a pH of 3. Additionally, the effects of various parameters, such as applied current and pH, were assessed. The results revealed that an increase in the current led to a higher reaction rate for the entire process, with the optimal conditions occurring at pH 3. The potential methyl orange degradation pathway was elucidated through a reactive oxygen species (ROS) test conducted during the electro-Fenton process.