Heterogeneous electro-Fenton Research Articles

Construction of a cathodic MOF/FeOOH heterojunction for boosted Fe(Ⅲ) reduction in electro-Fenton processes

This study developed a self-supported MOF/FeOOH heterojunction cathode without binders for boosted Fe(Ⅲ) reduction in heterogeneous electro-Fenton (EF) processes. The electron transport channels from FeOOH to in-situ grown NH2-MIL-88B(Fe) were established through the spontaneous formation of an internal electric field (IEF), which enhanced the electrical conductivity and disrupted the chemical inertness of the Fe(Ⅲ) reduction. The MOF/FeOOH cathode increased sulfamethazine (SMT) removal up to 95.76 %, 2.5 times better than using PTFE as binders. After ten-consecutive degradation experiments, the Fe(Ⅱ) content at cathode surface increased from 39.23 % to 56.73 %. Density functional theory (DFT) calculations and advanced characterization techniques demonstrated the efficient Fe(Ⅲ) reduction and H2O2 activation during the reaction. These results elucidate the promoting effect of modulating the “contact” between the catalyst and current collectors, as to provide a feasible and promising strategy for the development of efficient heterogeneous EF cathodes.

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.

Effective degradation of ciprofloxacin from aqueous solutions using heterogeneous electro-Fenton coupled with Fe@Fe2O3 core-shell nanoparticle

In the current research, a Ti/RuO2 anode and Fe@Fe2O3 catalyst were synthesized for electro-Fenton (EF) removal of ciprofloxacin (CIP). The results of the ANOVA from response surface methodology (RSM) indicated a significant relationship between experimental and predicted values. 100% CIP and 45% total organic carbon (TOC) removal were predicted at pH of 8.83, time of 14.80min, current density of 19.19mA/cm2, pollutant concentration of 15.13mg/L, and catalyst dosage of 199.03mg/L. Among the operational parameters, current density (F value = 191.90) and catalyst dosage (F value= 5.79) had the greatest and least effect on the CIP removal rate, respectively. The stability tests revealed excellent reusability of electrodes for long-term decomposition of CIP. The BOD5/TOC > 0.6 in the treated solution confirmed acceptable performance of the heterogeneous EF process in CIP degradation. A 25% growth inhibition rate of plant stems in the treated solution demonstrated the low toxicity and biodegradability of the effluent. The efficiency of the heterogeneous EF process for CIP removal in water matrices ranged from 43.65% to 100%. By evaluating the parameters, mineralization, production of different radicals, and energy consumption, the heterogeneous EF process can be considered for the effective decomposition of CIP from aqueous environments.

Synergistic enhancement of electro-Fenton redox processes by iron-molybdenum dual sites for synchronous removal of Cr (VI) and emerging organic pollutants

Synergy removal of heavy metals and emerging organic pollutants (EOPs) poses a formidable challenge in heterogeneous electro-Fenton processes. Here, we present a three-dimensional iron-doped molybdenum disulfide hierarchical microsphere/graphite felt (Fe-MoS2 HS/GF) system. This system exhibits exceptional electrocatalytic redox activity, achieving a 9.75-fold and 18.96-fold increase in Cr (VI) (2.38 × 10-2 min−1) and BPA (8.29 × 10-2 min−1) removal rates compared to the MoS2 HS/GF system, respectively. And it also exhibited a significantly enhanced mineralization efficiency (59.28 %) for BPA, surpassing that of the MoS2/GF system (5.75 %) by a factor of 10.31. Mechanistic insights indicate that the Fe-Mo dual catalytic sites effectively lower reaction barriers of H2O2 dissociation, generating significant amounts of ·OHsurface and 1O2 species for BPA degradation. Moreover, an electric field-driven the variable valence state of the Fe-Mo dual sites facilitates Fe (II) regeneration and Cr (VI) reduction. Notably, this system shows broad applicability for synchronous removal of Cr (VI) and diverse EOPs, exhibiting robust stability under unsteady-state continuous-flow operation (2 L reactor) with reduced biotoxicity in actual wastewater. This study highlights the synergistic benefits of the dual catalytic sites in the heterogeneous electro-Fenton processes for treating multicomponent wastewater.

Efficient generation of singlet oxygen (1O2) by CoP/Ni2P@NF for degradation of sulfamerazine through a heterogeneous electro-Fenton process at circumneutral pH

In electro-Fenton (EF), the development of a catalytic material with wide pH application range and high interference resistance is more suitable for practical wastewater treatment. In this study, the nanoneedle-shaped CoP/Ni2P heterostructure loaded onto a nickel foam substrate (CoP/Ni2P@NF) was successfully fabricated, which was used as a cathode material for heterogeneous electro-Fenton (Hetero-EF) to degrade sulfamerazine (SMR) at circumneutral pH. The SMR degradation efficiency within 90 min went to 100% and 87% at initial pH of 6.8 and 11, respectively. Experiments and theoretical calculations demonstrated that the heterostructure of CoP/Ni2P redistributed the interfacial charge and accelerated the electron transfer, resulting in different two-electron oxygen reduction (2e−ORR) selectivity and activity than CoP and Ni2P. The ion interference and complex water quality experiment exhibited that the degradation performance remained almost unchanged, showing better anti-interference ability and complex water quality applications. Through quenching experiments and EPR tests, it is confirmed that singlet oxygen (1O2) was the major reactive oxygen species (ROS) and 1O2 was converted from hydroxyl radical (·OH) adsorbed on the catalyst surface. This study provides an efficient catalyst for the application of Hetero-EF to remove organic compounds in complex water at circumneutral pH.

Bimetallic FeCu-MOF derivatives as heterogeneous catalysts with enhanced stability for electro-Fenton degradation of lisinopril

A bimetallic FeCu/NC core-shell catalyst, consisting in nanoparticles where zero-valent Fe and Cu atoms, slightly oxidized on their surface, are encapsulated by carbon has been successfully prepared by modifying the synthesis route of MIL(Fe)-88B. FeCu/NC possessed well-balanced textural and electrochemical properties. According to voltammetric responses, in-situ Fe(III) reduction to Fe(II) by low-valent Cu was feasible, whereas the high double-layer capacitance confirmed the presence of a great number of electroactive sites that was essential for continuous H2O2 activation to •OH via Fenton's reaction. Electrochemical impedance and distribution of relaxation times (DRT) analysis informed about the strong leaching resistance of FeCu/NC. To validate the promising features of this catalyst, the advanced oxidation of the antihypertensive lisinopril (LSN) was investigated for the first time. The heterogeneous electro-Fenton (HEF) treatment of 16.1 mg L−1 LSN solutions was carried out in a DSA/air-diffusion cell. At pH 3, complete degradation was achieved within 6 min using only 0.05 g L−1 FeCu/NC; at near-neutral pH, 100 % removal was also feasible even in actual urban wastewater, requiring 60–75 min. The FeCu/NC catalyst demonstrated high stability, still maintaining 86.5 % of degradation efficiency after 5 cycles and undergoing low iron leaching. It outperformed the monometallic (Fe/NC and Cu/NC) catalysts, which is explained by the Cu(0)/Cu(I)-catalyzed Fe(II) regeneration mechanism that maintains the Fenton's cycle. LC-MS/MS analysis allowed the identification of two main primary LSN by-products. It can then be concluded that the FeCu/NC-based HEF process merits to be further scaled up for wastewater treatment.

Heterogeneous electro-Fenton oxidation of Congo red using carboxylic group activated carbon felt cathode: Electrokinetic mechanism and performance

In this study, the carboxyl functional group (–COOH) saturated-carbon-felt (ACF) as functional cathode was prepared and used in heterogenous (Fe2+) electro-Fenton (EF) catalytic degradation of Congo red (CR) in waster. As a heterogeneous catalyst, size-controlled magnetite (Fe3O4) nanoparticles (MNPs) were applied to the surface of the ACF cathode. The selectivity of ACF toward the two-electron oxygen-reduction reaction was estimated based on the proportion of H2O2 production; it was determined as >89 %. The removal efficiency of ACF for CR dye was 94 ± 2 % over 40 min reaction time, almost double that of a pristine CF cathode (48 ± 3 %). The kinetics data fitted to a pseudo-second order (PSO) model with K2 of 8.8 × 10−4 ± 1.72 × 10−5 mol−1 cm3 min−1 (0.88 ± 0.02 M−1 min−1). The mineralization current efficiency and TOC for CR were observed as 58 ± 2 %, and 83 ± 3 %, respectively. Overall, the results insight that the system could be a viable alternative method for treating dye-contaminated water.

Endogenous iron-enriched biochar loaded nickel-foam cathode in electro-Fenton for ciprofloxacin degradation: performance, mechanism and DFT calculation

Steel mill wastewater sludge, with abundant endogenous iron resources, could be pyrolyzed into iron-enriched biochar (SBC) in one step and loaded onto nickel foam cathode (Ni-Foam) to construct a heterogeneous electro-Fenton system (SBC@Ni-Foam/EF). The purpose of this study were to optimize SBC@Ni-Foam/EF for efficient ciprofloxacin (CIP) removal, and its degradation mechanism and pathway in the presence of endogenous iron were elucidated by DFT calculation. The results showed that the highest CIP degradation efficiency (95.11 %) was achieved at a SBC pyrolysis temperature of 800 °C, an initial solution pH of 3, a Na2SO4 concentration of 0.05 mol L−1, a current density of 40 mA cm−2, and an aeration rate of 200 mL min−1. The degradation of CIP by SBC@Ni-Foam/EF was dominated by cathodic catalytic oxidation, and ·OH played a major role in the CIP degradation process. Combined with characterization and DFT calculation, the endogenous iron was dispersed in the stable Fe3O4 crystalline phase, which provided surface defects and catalytic sites for the cathode and promoted H2O2 activation to generate ·OH through iron cycling. The possible degradation pathways of CIP were proposed to include the cleavage of piperazine and quinolone rings, hydroxylation, and substitution or detachment of fluorine, etc., and the overall toxicity of the intermediates was alleviated after SBC@Ni-Foam/EF treatment. Therefore, this study was expected to achieve a win–win situation for iron-enriched sludge biomass resource utilization and CIP wastewater treatment.

Highly efficient FeS/Fe3O4 @ biomass carbon bifunctional catalyst with enriched oxygen vacancies for heterogeneous electro-Fenton catalysis

Low H2O2 production, narrow adaptive pH range and slow Fe(II) regeneration on the cathode still limit efficiency of electro-Fenton (EF) and its application. Herein, we designed a bifunctional catalyst with FeS and Fe3O4 nanoparticles dispersed on porous carbon (CFeS@C) using template of sodium alginate (SA)/FeSO4 hydrogel mixed with carbon black (CB), which presented high H2O2 generation efficiency and outstanding tetracycline degradation efficiency under wide pH ranges (3-8) with a low energy consumption of 19.6 kWh/kg total organic carbon (TOC). The introduction of CB created abundant oxygen vacancies in CFeS@C, promoting the oxygen adsorption and the electrochemical generation of H2O2, which further boosted the formation of •OH due to the interaction with Fe2+ on the cathode surface. Simultaneously, the reaction between the outer layer of FeS and Fe3+ not only accelerated iron cycling but also reduced the solution pH. It was verified that •OH and 1O2 played a dominant role in organics degradation. The system maintained stability after 10 cycles and effectiveness in the treatment of pharmaceutical wastewater. This study would offer a new strategy to develop an efficient and durable bifunctional catalyst for heterogeneous EF system working in wide pH conditions for wastewater treatment.

Enhanced heterogeneous electro-Fenton degradation of salicylic acid by different Fe3O4 loaded carriers

Different types of materials were used as catalyst carriers to enhance the degradation of salicylic acid in the heterogeneous electro-Fenton system. During the experiments, activated carbon, carbon felt and carbon cloth were selected as carbon based materials, and sodium alginate, chitosan and polyvinyl alcohol were chosen as polymer matrix, and foam metal included zinc foam, iron foam and nickel foam (NF). The changes of surface structure and morphology of the above carriers were studied, and combined with the effects of the carriers on the degradation of salicylic acid in the electro-Fenton system. The NF was the best carrier materials for the heterogeneous electro-Fenton system, and Ni and Fe3O4 had synergistic effect in enhancing redox reactivity. With salicylic acid concentration of 100 mg/L, the temperature of 25 ℃ and the pH of 7, the NF@Fe3O4 achieved the best salicylic acid degradation performance after reaction for 2 h. The NF@Fe3O4 enhanced the performance of the electro-Fenton system, which provided a valuable reference for the application of heterogeneous catalyst carriers in the electro-Fenton system.

Vanadium doped Fe-Mn bimetallic oxides as cathodic materials for boosted heterogeneous electro-Fenton degradation of organic contaminants

The design of cathode materials with both sustainable H2O2 selectivity and accelerated recyclable regeneration remains a challenge for contaminants removal in heterogeneous electro-Fenton (HEF) process. Herein, a series of ternary Fe0.50Mn0.5−δVδOx (δ = 0.005, 0.01, 0.05) metal oxides have been synthesized and employed as cathodic materials for the degradation of various organic contaminants in water matrix. 99.7 % removal rate was achieved for carbamazepine (CBZ) in 60 min with 98.8 % mineralization rate. Simultaneously, the catalyst exhibited outstanding degradation efficiency (96.0–99.7 %) with other pollutants including sulfonamides (SMX), bisphenol A (BPA), 2,4-dichlorophenol (2,4-DPC) and ofloxacin (OFX), demonstrating its potential application. Factors affecting the EF process, including current density, pH, oxygen flow rate and compatibility of inorganic anions were thoroughly evaluated and the degradation mechanism was studied in detail. Density functional theory (DFT) calculations revealed that the improved catalytic efficiency was originated from vanadium doping to access optimized electronic structure, which endows enhanced 2e− ORR selectivity as well as excellent overall performance for the EF process. This work may enrich the study on EF system and offers a promising strategy for contaminants removal with FeMnVO materials in water treatment applications.

Improvement of heterogeneous electro-Fenton oxidation of dimethyl phthalate by embedding Fe/Co bimetallic active sites into waste wine lees biochar

Phthalates (PAEs) are frequently detected in the water environment and pose a severe threat to the ecosystem and human health. Electro-Fenton technology is regarded as an effective approach to degrade PAEs; however, the preparation of inexpensive and efficient cathode materials has restricted its further application. In this study, Fe/Co bimetallic sites were incorporated into solid waste wine lees to synthesize highly active heterogeneous catalyst, and dimethyl phthalate (DMP) was chosen as the target pollutant to investigate the activity of the catalyst. Both the degradation of DMP and the removal of total organic carbon (TOC), the performance of Fe/Co co-modified biochar (FeCo@NOPC) is superior to that of Fe (Co) alone (Fe@NOPC/Co@NOPC) and modified biochar (NOPC). Under neutral conditions. Within 5 h, the DMP removal rate reached 89 % and TOC was reduced by approximately 40 %. The mechanism study reveals that the degradation of DMP is mainly attributed to the OH generated by the cathode, and the anodic oxidation and cathode adsorption only play minor roles. Finally, the degradation path of DMP was analyzed by LC-MS technique. This study offers a novel way to utilize solid waste and reduce the cost of heterogeneous electro-Fenton system.

Amorphous CoSx in heterogeneous electro-Fenton: A 1O2-mediated system for efficient and selective water decontamination

Heterogeneous electro-Fenton (hetero-EF) technology represents a promising and safe approach to water treatment. However, conventional hetero-EF catalysts still face the challenges of removing contaminants selectively and operating efficient in complex water quality. We proposed a novel system utilizing amorphous CoSx (A-CoSx) that overcame these limitations. This material generated only singlet oxygen (1O2), a highly specific oxidant, for contaminants degradation. Unlike traditional crystalline catalysts, A-CoSx efficiently utilized hydrogen peroxide (H2O2) to directly produce 1O2, exhibiting high catalytic activity across a wide pH range (3.0–11.0). The formation mechanism of 1O2 was confirmed through experimental investigations, density functional theory (DFT) calculations, and advanced characterization techniques. This system effectively degraded contaminants even in complex water with interferences and enabled selective targeting of pollutants with electron-donating groups. This innovative approach using amorphous materials offers a promising strategy for the regulation of ROS and enabling selective contaminant removal in water treatment.

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.

In-situ interconnected 1D/2D/3D architectures of CNT/MoS2/Fe3O4 membranes for increasing degradation efficiency of penetrative electro-Fenton under low energy consumption

The electro-Fenton oxidation process for the degradation of organic pollutants in recalcitrant wastewater has garnered significant attention and research efforts in the field of advanced water treatment. This is primarily due to its highly effective degradation capabilities and the advantages it offers, including the avoidance of unsafe transportation and storage of hydrogen peroxide (H2O2). However, challenges such as relatively high energy consumption, complex operational requirements, and limited operational stability continue to pose significant economic constraints on the widespread application of electro-Fenton technology in water purification. In this study, we employed a secondary hydrothermal method to construct a multi-layered CNT/MoS2/Fe3O4 composite heterostructure in situ. Leveraging the synergistic effects of the introduced variable valence elements, Fe and Mo, and the interconnected multi-layered membrane structure, the CNT/MoS2/Fe3O4 electro-Fenton membrane holds promise in a permeable filtration system. Under the conditions of a current density of 1.50 mA/cm² and an electrolyte concentration of 0.50 mol/L, the CNT/MoS2/Fe3O4 composite membrane exhibited a degradation efficiency of over 90.00 % for 100.00 mg/L RhB within 10 minutes, and the degradation rate approached nearly 99.00 % at 60 minutes. Furthermore, the degradation efficiency for various recalcitrant organic dye wastewaters, including phenol, methyl orange, and methylene blue, could be maintained at levels ranging from 80.00 % to 97.00 %. Particularly, under optimized operating conditions, the specific energy consumption (EC) for the CNT/MoS2/Fe3O4 membrane process was measured at 0.60±0.01 kWh/m³, showcasing exceptionally low energy consumption characteristics. In conclusion, it is expected to contribute to the reduction of the overall consumption of heterogeneous electro-Fenton oxidation systems and enhance their operational efficiency. This innovative approach represents a significant advancement in the field, offering the potential to address the economic limitations associated with electro-Fenton technology in water quality purification.

Remarkable mass-transfer enhancement via constructing ordered framework structure by 3D-priniting strategy for stable pesticides removal

Heterogeneous electro-Fenton (HEF) processes are potential pathways for aquatic contaminants removal. However, synergies from catalysts dense accumulation, the sluggish inner diffusion and the loss of active sites inside the catalyst, have limited the practical application of traditional monolithic cathodes. In this work, it has been proofed that the highly controlled porosity in 3D-printed ordered framework shows obvious diffusion enhancement and offers more active sites. The stable and efficient HEF catalysts guarantee the removal and mineralization of aqueous pesticides. H2O2 is effectively generated in situ via 2-electron oxygen reduction reaction by the carbon lattice in the pH range of 4–10, which is then activated into hydroxyl radicals by the encapsulated Fe2P/Fe in 3D printed cathodes. Estimated by the mass-transfer simulation, the Grid structure has the largest convective transport velocity of 8 × 10-5 m∙s-1, which optimizing mass-transfer effect and maximizing the active sites utilization. Grid-2 % achieves 3.54 ± 0.05 mg∙g-1 napropamide degradation at neutral condition in one hour, which is 82 % and 269 % higher than degradation obtained by Star-2 % and Diamond-2 %, respectively.

Degradation of antiviral drug molnupiravir using a dual function FeIIFeIIILDH@carbon felt cathode in the heterogeneous electro-Fenton process: Kinetics and mineralization study

Pharmaceuticals constitute one of the more widely reported anthropogenic micropollutants, and their removal usually requires a specific treatment method. The oxidative degradation and mineralization of molnupiravir (MNP), a novel antiviral drug used for COVID treatment, were investigated for the first time by EF processes using both raw carbon felt (CF) and modified dual-function CF cathodes. The classical electro-Fenton (CEF) process using CF cathode has significant challenges, including a narrow pH range and a lack of ability to reuse the catalyst. To overcome these limitations, a dual-function FeIIFeIII layered double hydroxide modified carbon felt (FeIIFeIIILDH@CF) cathode was developed using a hydrothermal method. The FeIIFeIIILDH@CF cathode was characterized using BET, FTIR, SEM, cyclic, and linear sweep voltammetry. The efficiency of FeIIFeIIILDH@CF cathode for the removal of MNP compared with that of raw carbon felt (CF) cathode, including the effects of operating parameters. The heterogeneous electro-Fenton (HEF) process with FeIIFeIIILDH@CF cathode allowed an almost complete mineralization (98.08 % TOC removal) of 0.1 mM MNP solution. The mineralization ability of the FeIIFeIIILDH@CF cathode was more than 95 % after 5 cycles, suggesting a good reusability of the synthesized cathode. The absolute rate constant for the oxidation of MNP with ●OH (2.22 ± 0.03 ×109 M−1 s−1) was also determined for the first time. In addition, the modified LDH cathode has the advantage of being effective over a wide pH range while avoiding the use of an iron salt as a catalyst.

High efficiency two-step electrocatalysis boosted by dual-motif bridge Co-S-Mo for Heterogeneous Electro-Fenton: Enhanced H2O2 production and fluoxetine elimination synergistic mechanism

Heterogeneous electro-Fenton process is widely recognized as intensive in-situ strategy with environmental compatibility. However, the simultaneous elevation of H2O2 production and exploitation efficiency during electrocatalysis remains a challenge. Here, we propose an innovative dual-site catalyst (MoxCo9xS8yNy; MCN) with Mo active motifs for enhanced two-electron oxygen reduction reaction and Co active motifs for enhanced reactive oxygen species generation to promote H2O2 generation and fluoxetine (FLX) degradation. As determined by Mo scaling and application performance, the optimal MCN catalyst provided at least 20 % increase in contaminant elimination within 30 min, reduced the reaction potential by over 1.4 eV, and diminished environmental exposure to toxic products. The optimal MCN@CF cathode efficiently removed approximately 96.7 % FLX and 55.1 % total organic carbon at a pH of 3 within 35 min. The critical dual-motif bridge Co–S–Mo mediated by S could disrupt the synergistic *O and *OOH binding energies, significantly penetrating the catalysis barriers. This work unravels the structural optimization evolution of non-single-site catalysts, providing new solutions to the refractory issues of wastewater decontamination.

Integrated Heterogeneous Electro-Fenton Process and Constructed Wetland for the Treatment of Stabilized Landfill Leachate

Treatment of stabilized landfill leachate is a great challenge due to its poor biodegradability. Present study made an attempt to treat this wastewater by combining electro-Fenton (E- Fenton) and constructed wetland (CW). E-Fenton treatment was applied prior to Constructed wetland process to enhance the biodegradability of leachate, which will be beneficial for the subsequent biological process. This study also investigates the efficiency of Magnetite (Fe3O4) nanoparticles as a heterogeneous catalyst in E-Fenton process. The objectives of this study are to synthesize chitosan to obtain magnetite nanoparticles via iron ions assembly and to characterize the synthesized nanoparticles using SEM, XRD and FTIR analysis to assess its nature. The effects of initial pH, catalyst dosage, applied voltage and electrode spacing on Chemical Oxygen Demand (COD) removal efficiency were analysed to determine the optimum conditions. Heterogeneous E-Fenton process gave 84.29% COD removal at catalyst dosage of 50 mg/L, pH 2, electrode spacing 3 cm, voltage 5 V and electrode area 25 cm2. The proficiency of utilizing eggshells as a media in constructed wetlands was evaluated for the treatment of wastewater previously subjected to electro-Fenton treatment. And it was found that combined E-Fenton and biological treatment (CW) resulted in overall COD removal of 95.79%, bringing down the final COD to 292 mg/L. Thus, the combination of the E-Fenton process followed by a biological process is efficient for complete mineralization with lower operational cost.

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.