electro-Fenton Process Research Articles

Insights into antibiotic cefaclor mineralization by electro-Fenton and photoelectro-Fenton processes using a Ti/Ti4O7 anode: Performance, mechanism, and toxic chlorate/perchlorate formation

A comparative degradation of antibiotic cefaclor (CEC) between Ti/Ti4O7 and Ti/RuO2 anodes, in terms of degradation kinetics, mineralization efficiency, and formation of toxic chlorate (ClO3−) and perchlorate (ClO4−), was performed with electrochemical-oxidation (EO), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes. Besides, CEC degradation by EF with boron-doped diamond (BDD) anode was also tested. Results showed CEC decays always followed pseudo-first-order kinetics, with increasing apparent rate constants in the sequence of EO < EF < PEF. The mineralization efficiency of the processes with Ti/Ti4O7 anode was higher than that of Ti/RuO2 anode, but slightly lower than that of BDD anode. Under the optimal conditions, 94.8% mineralization was obtained in Ti/Ti4O7-PEF, which was much higher than 64.4% in Ti/RuO2-PEF. The use of Ti/RuO2 gave no generation of ClO3− or ClO4−, while the use of Ti/Ti4O7 yielded a small amount of ClO3− and trace amounts of ClO4−. Conversely, the use of BDD led to the highest generation of ClO3− and ClO4−. The reaction mechanism was studied systematically by detecting the generated H2O2 and •OH. The initial N of CEC was released as NH4+ and, in smaller proportion, as NO3−. Four short-chain carboxylic acids and nine aromatic intermediates were also detected, a possible reaction sequence for CEC mineralization was finally proposed.

A review of electro-Fenton and ultrasound processes: towards a novel integrated technology for wastewater treatment.

Nowadays, the presence of persistent dissolved pollutants in water has received increasing attention due to their toxic effects on living organisms. Considering the limitations of conventional wastewater treatment processes for the degradation of these compounds, advanced oxidation processes such as electro-Fenton and sono-chemical process, as well as their combination, appear as potentially effective options for the treatment of wastewater contaminated with bio-recalcitrant pollutants. In view of the importance of the development of processes using real effluents, this review aims to provide a comprehensive perspective of sono-electro-Fenton-related processes applied for real wastewater treatment. In the first section, the fundamentals and effectiveness of both homogeneous and heterogeneous electro-Fenton approaches for the treatment of real wastewater are presented. While the second part of this work describes the fundamentals of ultrasound-based processes, the last section focuses on the coupling of the two methods for real wastewater treatment and on the effect of the main operational parameters of the process. On the basis of the information presented, it is suggested that sono-electro-Fenton processes substantially increase the efficiency of the treatment as well as the biodegradability of the treated wastewater. The combined effect results from mass transfer improvement, electrode cleaning and activation, water electrolysis, and the electro-Fenton-induced production of hydroxyl radicals. The information presented in this work is expected to be useful for closing the gap between laboratory-scale assays and the development of novel wastewater technologies.

Dual-functional single-atomic Mo/Fe clusters–decorated C3N5 via three electron-pathway in oxygen reduction reaction for tandemly removing contaminants from water

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

Petroleum refinery wastewater treatment using a novel combined electro-Fenton and photocatalytic process

In the current study, treatment of petroleum refinery wastewater has been successfully achieved using a novel photocatalysis-ElectroFenton system operated at a batch circulation mode and composed from a tubular electro-Fenton reactor provided with a macro-porous graphite air diffusion cathode (MPGADC) combined with a new configuration of photo reactor. The feasibility of the combined electro-Fenton with photo-catalytic process (EF + UV/ TiO2) was evaluated using response surface methodology (RSM) with Box-Behnken design (BBD). Titanium dioxide (Anatase) was used as a photo-catalyst and characterized by x-ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller surface area (BET). Four main operating variables were studied: current density (5–15 mA/cm2, Fe2+concentration (0.1–0.5 mM), TiO2 dosage (0.1–0.7 g/l), and reaction time (20–60 min). Results revealed that reaction time has the most effective parameter on the EF + UV/ TiO2 process followed by TiO2 dosage, Fe2+concentration, and current density. The optimum operating conditions for maximizing COD removal (RE%) and minimizing the total electrical energy consumption (EECT)) were found to be a current density of 15 mA/cm2, Fe2+ concentration of 0.5 mM, TiO2 dosage of 0.7 g/l, and a reaction time of 54 min in which COD removal of 91.26 % was achieved with claiming EECT of 26.86 kWh/m3. Results revealed a vital improvement of using EF + UV/ TiO2 in comparison with UV/ TiO2 alone where an enhancement of 23% in RE% and a reduction by 55% of EECT were observed. Furthermore, a kinetic study was performed for EF + UV/TiO2 and UV/ TiO2 alone in which the results revealed that decay of COD obeyed a pseudo-first-order kinetic for the two processes with a high-rate constant for EF + UV/ TiO2 process.

Efficient degradation of refractory pollutant boosted by combining heterogeneous electro-Fenton on the hydrophobic modified gas diffusion electrode with anodic oxidation

To boost refractory pollutant removal over a broad pH range, we here proposed an integrated electrocatalytic process combining electrochemical anodic oxidation (AO) with cathodic electro-Fenton (EF) based on a hydrophobic modified gas diffusion electrode and heterogeneous Fenton catalyst of FeOCl. Total organic carbon (TOC) removal of refractory levofloxacin by EF + AO process was 85% in 120 min under the applied potential of −0.6 V and pH ∼6.7, obviously higher than that of only AO (22%) or EF (62%) process. Significantly, EF+AO process was demonstrated to be efficient and stable for actual wastewater treatment that chemical oxygen demand (COD) value of refinery wastewater after EF + AO treatment was steadily met the discharge standard (GB 18918–2002) for sewage treatment plants in China (I-A: COD < 50 mg/L) during 100 h of consecutive runs. Our results provide new insights into developing an energy-efficient electrocatalytic technology for enhancing refractory pollutant removal.

Electrochemical impedance spectroscopy study of a cavitation assisted electro-Fenton process

In this work, we report the results of a study to detect and quantify the discoloration of a model dye by an electro-Fenton process, in the presence and in the absence of ultrasound induced cavitation. As expected, a substantial increase in the color removal rate of the solution was observed, reflecting a strong synergetic interaction between the electrochemically induced discoloration kinetics and the ultrasound promoted cavitation. Control experiments to assess the dye degradation kinetics due to pure cavitation, also revealed that the synergetic effect under study takes place at the electrode-solution interphase. In order to gain understanding on the nature of the synergy observed, an electrochemical impedance spectroscopy (EIS) study was carried out. The fitted results of the experimental data suggest that, while the effects of ultrasonic cavitation are significant at the carbon cathode|electrolyte interphase, even in the absence of dissolved O2 gas, the effect is comparatively negligible in the bulk of the solution as well as in the electrolyte located inside the pores of the carbon electrode. EIS results also suggest that the synergy observed during the cavitation assisted electrochemical generation of OH radicals in the absence of dissolved O2, points to the future development of novel wastewater treatment processes that, using air saturated solutions, will overcome the low solubility of O2 that frequently limits traditional electro-Fenton approaches.

Modification of Electro-Fenton Process with Granular Activated Carbon for Phenol Degradation – Optimization by Response Surface Methodology

Modification of Electro-Fenton Process with Granular Activated Carbon for Phenol Degradation – Optimization by Response Surface Methodology

Evaluation of the performance of heterogeneous electroFenton process with carbon nanotube/Fe@Fe2O3 for the degradation of amoxicillin from aqueous solutions

Evaluation of the performance of heterogeneous electroFenton process with carbon nanotube/Fe@Fe2O3 for the degradation of amoxicillin from aqueous solutions

Direct-writing of three-dimensional porous Fe3N/FeS electrode for efficient degradation of organic pollutants in water through Electro-Fenton process

The Electro-Fenton process is getting a rapid development recently as a novel advanced electro-oxidation technology for the removal of organic pollutants from water. In this work, a three-dimensional (3D) porous Fe3N/FeS composite electrode was created from a Fe2(SO4)3-based composite ink by the direct-writing 3D printing technology combined with a high temperature heat treatment under ammonia atmosphere. Fe3N served as the conductive skeleton of the electrode, while FeS could provide Fe2+ to react with in-situ generated H2O2 in the Electro-Fenton process to generate ·OH radicals. Thus, it could eliminate the need of external ferrous ion addition. The 3D porous Fe3N/FeS composite electrode had desired 3D interconnected macro-channels for efficient mass transport and rough rod surfaces to provide more active sites, which resulted in its superior degradation performance on organics than its traditional two-dimensional (2D) plate counterpart. A two-step H2O2 production path was found on the 3D Fe3N/FeS composite electrode, which had been found to possess a faster reaction kinetics. It effectively degraded rhodamine B (RhB) within a wide pH range from ∼3 to ∼ 10, demonstrated stable performances in repeated uses, and had low iron ion leaching, all of which were beneficial for its potential applications. Furthermore, it also demonstrated effective degradation performances on antibiotics of amoxicillin (AMX) and tetracycline hydrochloride (TC-HCl) in both deionized (DI) water and tap water matrixes, indicating its potential to solve the emerging contaminant problem in real water treatment practices.

Removal Of Sumifix Yellow EXF Reactive Azo Dye By Electro-Fenton Method

Reactive dyes can be found in large quantities in textile industry wastewater due to their widespread use for dyeing cotton fabrics and their durable nature. In the treatment of wastewater containing dyestuffs in this class, advanced treatment methods have become necessary due to the inadequacy of conventional treatment methods and their disadvantages. For this reason, electro-Fenton, an electrochemical advanced oxidation method, is a strong alternative as a treatment technology that provides complete disintegration of dye molecules. In this study, the electro-Fenton method was used to treat model wastewater containing the reactive azo dye Sumifix Yellow EXF. The electro-Fenton process is based on the in situ generation of hydroxyl radicals (⦁OH), a strong oxidant, using Fe2+ and H2O2 released at the electrodes or added from outside. In the electrochemical cell used, carbon fiber was used as the cathode and iron was used as the anode. While Fe2+ ion was produced at the anode, H2O2 was added to the cell externally. In the experiments carried out at room temperature, a 250 mL glass beaker was used as a reactor. In the study, the optimization of the parameters was achieved by using the classical experimental design method. According to this method, one parameter is changed and other parameters are kept constant. In order to achieve the highest dyestuff removal, experiments were conducted by varying the voltage (5–10 V), H2O2 concentration (9–74 mM), Na2SO4 concentration (6–25 mM), and pH (3-5), and the impact of these factors on dye removal and energy consumption was evaluated. It was found that for the best dye removal, voltage is 7.5 V, the H2O2 concentration is 74 mM, the Na2SO4 concentration is 25 mM and the optimum pH value is 4. At these values, 98.14% removal at 30 minutes was achieved with an energy consumption of 7.98 Wh/L. The electro-Fenton method was found to be a highly effective approach for wastewater treatment and environmental remediation, showing remarkable dye removal efficiency with reasonable energy consumption under optimized conditions.

Facile synthesis of bimetallic ACF/CC@FeOCl–Cu composite cathode for efficient degradation of sulfamethoxazole at neutral pH by a flow-through heterogeneous electro-Fenton process

Flow-through heterogeneous electro-Fenton (FHEF) process shows a broad prospect for refractory organic pollutants removal. However, maintaining a long-term service life of higher catalytic cathode is crucial for the development of cathode materials, especially for iron-functionalized cathode operated under harsh conditions. In this study, a novel bimetallic CC@FeOCl–Cu composite was synthesized through one-step calcination, coupled with a series of microstructure characterization methodology, including XRD, SEM-EDS, XPS, and FTIR. The superior catalytic activity of CC@FeOCl–Cu could be ascribed to Fe–Cu synergy and better dispersion of FeOCl nanosheets. With the optimal Cu:Fe ratio of 1:60, the bifunctional ACF/CC@FeOCl–Cu cathode was employed in FHEF process, exhibiting an outstanding performance for sulfamethoxazole (SMX) removal over a wide pH range (3.0–9.0). Comparison of experimental results indicated that the ACF/CC@FeOCl–Cu-FHEF process showed higher performance than ACF/CC@FeOCl-FHEF and homogeneous EF processes. The average SMX removal efficiency was 98% and TOC removal efficiency was more than 57% even after 10 cycles. Radical quenching experiments and electron spin resonance test confirmed that •OH was the primary active species. More •OH was generated in the ACF/CC@FeOCl–Cu-FHEF process because the doping of Cu could enhance catalytic activity of cathode. In addition, the satisfactory performance could be observed in the ACF/CC@FeOCl–Cu-FHEF process for the treatment of real landfill leachate, indicating its potential for practical application in wastewater treatment.

Comparison of Electro-Fenton and Photoelectro-Fenton for removal of Acrylonitrile Butadiene Styrene (ABS) from petrochemical wastewater

The purpose of this study was the evaluation the Electro-Fenton (EF) and Photo Elecro-Fennton (PEF) efficiencies to remove of some pollution indicators from effluents of Acrylonitrile Butadiene Styrene (ABS) petrochemical industries affected by the operational parameters such as operation time, pH, current density, and concentration of H2O2. The EF and PEF reactors were made and a batch study was performed to optimize the operational parameters. The optimum operating conditions were determined as pH 5, reaction time 60 min, H2O2 concentration 50 mmol/lit and current density 20 mA/cm2 for EF process and pH 5, operation time 30 min, H2O2 concentration 25 mmol/lit, current density of 20 mA/cm2 for PEF process. The highest removal efficiencies of COD (chemical oxygen demand), turbidity, total kejaldahl nitrogen (TKN) and total suspended solids (TSS) by EF and PEF processes under optimal conditions were obtained 86.7, 88.1, 67.9 and 64.1% for EF and 92.4, 93.7, 70.5 and 67.2% for PEF process, respectively. The PEF process resulted in higher removal efficiencies than that of the EF process to remove COD and TKN especially. Also, the amount of energy consumption for EF and PEF were obtained 10.1 and 9.3 kW h/m3, respectively. The PEF process was more capable to remove the pollutants from wastewater, than the EF process in a shorter time and with a lower H2O2 concentration due to the presence of UV radiation, which causes the photocatalytic decomposition of organic pollutants.

Heterogeneous electro-Fenton system using Fe-MOF as catalyst and electrocatalyst for degradation of pharmaceuticals

In recent years, heterogeneous electro-Fenton processes have gained considerable attention as an alternative to homogeneous processes. In this context, the aim of this study is the use of a commercial iron metal-organic framework (Fe-MOF), Basolite® F-300, as a base material for the design of a heterogeneous electro-Fenton treatment system for the removal of antipyrine. Initially, the catalyst was applied as powder in aqueous solution and three key parameters of the electro-Fenton process (pH, Fe-MOF concentration and current density) were evaluated and optimized by a Central Composite Design Face Centred (CCD-FC) using antipyrine removal and energy consumption as response functions. Near complete antipyrine removal (94%) was achieved under optimal conditions: pH 3, Fe-MOF 157.78 mg/L and current density 6.67 mA/cm2, obtaining an energy consumption of 0.29 W·h per mg of antipyrine removed. Later, two electrocatalysts (Fe-MOF functionalized cathodes), prepared by different Fe-MOF immobilisation approaches (composite of carbon black/polytetrafluoroethylene or by electrospinning on Ni foam), were synthesized. Their characterisation showed notable Fe-MOF incorporation into the material and favourable properties as electrocatalysts. Both Fe-MOF functionalized cathodes were evaluated in the removal of antipyrine at different pH (acidic and natural) and current density (27.78 and 55.56 mA/cm2), achieving in the best conditions removal levels around 80% in 1 h without any operational problems. In addition, several intermediates generated during the treatment were identified and their toxicity estimated. According to the obtained results, the degradation compounds have less toxicity than the parent compounds, confirming the effectiveness of the treatment.

Removal of pharmaceuticals and personal care products from wastewater via anodic oxidation and electro-Fenton processes: current status and needs regarding their application.

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.

The strong metal–support interactions induced electrocatalytic three-electron oxygen reduction to hydroxyl radicals for water treatment

As a promising environmental remediation technology, the electro-Fenton (EF) process is mainly limited by the two rate-limiting steps, which are H2O2 generation and activation. The electrocatalytic three-electron oxygen reduction reaction (3e- ORR) can directly activate oxygen to hydroxyl radicals (•OH), which is expected to break through the rate-limiting steps of the EF process. However, limited success has been achieved in the design of 3e- ORR electrocatalysts. Herein, we propose Cu/CoSe2/C with the strong metal-support interactions to enhance the 3e- ORR process, exhibiting remarkable reactivity and stability for •OH generation. Both experiment and DFT calculation results reveal that CoSe2 is conducive to the generation of H2O2. Meanwhile, the metallic Cu can enhance the adsorption strength of *H2O2 intermediates and thus promotes the one-electron reduction to •OH. The Cu/CoSe2/C catalyst exhibits the electron-transfer number close to 3.0 during the ORR process, and exhibits the outstanding •OH generation performance, achieving a higher apparent rate constant (6.0 times faster) toward ciprofloxacin compared with its analogy without the SMSI effect. Our work represents that the SMSI effect endows Cu/CoSe2/C high activity and selectivity for •OH generation, providing a unique perspective for the design of a high-efficiency 3e- ORR catalyst.

Carbon Gels-Green Graphene Composites as Metal-Free Bifunctional Electro-Fenton Catalysts.

The Electro-Fenton (EF) process has emerged as a promising technology for pollutant removal. However, the EF process requires the use of two catalysts: one acting as an electrocatalyst for the reduction of oxygen to H2O2 and another Fenton-type catalyst for the generation of ·OH radicals from H2O2. Thus, the search for materials with bifunctionality for both processes is required for a practical and real application of the EF process. Thus, in this work, bifunctional electrocatalysts were obtained via doping carbon microspheres with Eco-graphene, a form of graphene produced using eco-friendly methods. The incorporation of Eco-graphene offers numerous advantages to the catalysts, including enhanced conductivity, leading to more efficient electron transfer during the Electro-Fenton process. Additionally, the synthesis induced structural defects that serve as active sites, promoting the direct production of hydroxyl radicals via a 3-electron pathway. Furthermore, the spherical morphology of carbon xerogels enhances the accessibility of the reagents to the active sites. This combination of factors results in the effective degradation of Tetracycline (TTC) using metal-free catalysts in the Electro-Fenton process, achieving up to an impressive 83% degradation without requiring any other external or additional catalyst.

In-situ investigation into the dynamic evolution of electrode surface H* and H* mediated pH-independent and residue-free electro-Fenton process

The practical use of Fenton process has been thus far limited by the harsh pH and accumulation of iron-rich sludge, while these two shortcomings will be tackled hopefully via developing non-metallic-catalyzed green Fenton-like approach. Herein, we investigate in-situ the dynamic evolution of electrode surface atomic hydrogen (H*) and H* mediated pH-independent and residue-free electro-Fenton process via operando electrochemical investigation and visualization techniques. The H* generated on the surface of palladium-coated electrode enables effective activation of hydrogen peroxide (H2O2) to generate hydroxyl radical (OH) for efficient bisphenol A degradation (>99%), validated by in-situ cyclic voltammetry and electron spin resonance. Meanwhile, in-situ Raman spectra confirms that H2O2 is activated through a transition state of *H3O2 adduct with a low reaction energy barrier of 0.51 eV, whereby the lone electron in H* can readily cleave peroxide bond to produce OH and H2O as the only products (ΔG = −1.03 eV). More importantly, the electron-driven H* production is independent of the solution pH as both H+ and H2O can act as precursors verified by in-situ fluorescence analyses, so that the H2O2 activation mediated by H* extends successfully to a wider pH range (3–10). Our research provides a promising path toward eliminating restrictions of traditional Fenton process and paves the way simultaneously for in-situ investigation into reaction mechanism of such electrochemical processes.

Enhanced generation of reactive radicals and electrocatalytic oxidation of levofloxacin using a trimetallic CuFeV layered double hydroxide-containing electrode

In Electro-Fenton (EF) processes, the use of iron as a catalyst under acidic conditions results in increased costs and potential secondary pollution. To address these issues, we developed a CuFeV layered double hydroxide (LDH) coating on graphite felt (GF) (CuFeV LDH@GF) that offers an effective performance across a broad pH range without causing metal pollution. The CuFeV LDH@GF cathode exhibited a good oxygen reduction performance, high stability, and an efficient removal of levofloxacin (LEV) over a wide pH range (pH = 3–10). The simultaneous presence of Cu2+/Cu3+, Fe2+/Fe3+, and V4+/V5+ redox pairs played a crucial role in facilitating interfacial electron transfer, thereby enhancing the production and subsequent activation of H2O2 within the system. The apparent rate constant (kapp) of LEV removal under neutral conditions with the CuFeV LDH@GF electrode was more than twice that of the raw GF electrode. This improvement can be attributed to the CuFeV LDH coating, which increased the generation of hydroxyl radicals (•OH) from 0.64 to 1.27 mM. Importantly, the CuFeV LDH@GF electrode maintained its efficiency and stability even after 10 reuse cycles. Additionally, GC–MS analyses revealed the degradation of intermediate compounds, which included cyclic and aliphatic compounds. This study provides significant insights into the synergistic effects of trimetallic LDHs, contributing to the development of high-performance cathodes.

Characterization of Bismuth Composited to Carbon Nanotube-Coated Titanium Cathode in Electro-Fenton System

Bismuth (Bi) is a highly reactive catalyst for the generation of hydroxyl (∙OH) radicals. Cathodes constructed from composites of Bi and carbon nanotube (CNT) exhibit high stability and low resistance, which enhance their electron transfer capability. In this work, a titanium substrate was coated with multi-walled carbon nanotube (MWCNT/Ti) using electrophoretic deposition process, followed by electrodeposition of Bi onto the MWCNT-coated Ti (Bi/MWCNT/Ti). The effects of Bi electrodeposition time on the surface morphology of Bi/MWCNT/Ti cathodes were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy, and the electrochemical characteristics of each cathode were identified via a series of electrochemical analyses further. The results demonstrated that electrodeposition at −0.85 V vs. Ag/AgCl for 5 min revealed uniform distribution of dense Bi across the surface of cathode, which provides better hydrophilicity for cathode and promotes highest electron transfer rates, respectively; when the Bi/MWCNT/Ti cathode was used as an electro-Fenton (EF) cathode, the EF system achieved a rhodamine B degradation rate of 80.8% after 30 min, which is a significant increase (83.63%) than the unmodified Ti cathode. The use of Bi in EF cathodes improves the efficiency of the EF process.

Efficient degradation of carbamazepine using a modified nickel-foam cathode (Ni-FM/CNTs) in penetrating electro-Fenton process

A modified nickel-foam (Ni-FM) cathode coated with multi-walled carbon nanotubes (Ni-FM/CNTs) was synthesized for carbamazepine (CBZ) highly energy-efficient degradation in penetrating electro-Fenton. Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD) test proves that multi-walled CNTs were successfully coated on the surface of nickel foam. The linear sweep voltammetry (LSV) results revealed the greater electrochemical activity of Ni-FM/CNTs compared to Ni-FM. The H2O2 accumulation performance tests showed that Ni-FM/CNTs cathode had higher H2O2 accumulation performance than Ni-FM cathode, and the H2O2 yield of Ni-FM/CNTs was 5.7 times higher than that of Ni-FM after 1 h of electrolysis. The reaction rate of CBZ degradation in penetrating electro-Fenton process was 2.5 times that of planar electro-Fenton process because the flow-through process enhanced O2 mass transfer and promoted the production of H2O2. The Box-Behnken Design response surface method was used to analyze the factors affecting the degradation efficiency of CBZ in the penetrating electro-Fenton process. The CBZ degradation efficiency could reach 100%, and electric energy consumption was 0.4356 Wh/L at current density of 9 mA/cm2, pH = 3, concentration of Fe2+ was 0.3 mM, and the through-flow velocity of 60 mL/min. The quenching experiment and EPR test results confirmed the degradation of CBZ was mainly the oxidation of·OH, and O2-·is the prerequisite for the production of·OH. Eight possible degradation products of CBZ degradation were identified and the probable degradation route was proposed. The ECOSAR program was used to predict the toxicities of CBZ and its degradation products, and the consequences revealed that the electro-Fenton process has a detoxification effect on CBZ, but may also produce more toxic organic compounds than the parent compound.