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Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process. [ABSTRACT FROM AUTHOR]

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

This study deals with the elimination of methyl orange (MO) from an aqueous solution by utilizing the 3D electroFenton process in a batch reactor with an anode of porous graphite and a cathode of copper foam in the presence of granular activated carbon (GAC) as a third pole, besides, employing response surface methodology (RSM) in combination with Box-Behnk Design (BBD) for studying the effects of operational conditions, such as current density (3–8 mA/cm² ), electrolysis time (10–20 min), and the amount of GAC (1–3 g) on the removal efficiency beside to their interaction. The model was veiled since the value of R² was high (>0.98) and the current density had the greatest influence on the response. The best removal efficiency (MO Re%) at pH = 3 was 95.62% with an average energy consumption of 6.22 kWh/kg MO, which was achieved under maximal conditions of current density = 5.12 mA/cm², mass of GAC = 3 g, and time = 20 min with small amounts of Fe2+ (0.124 mM), and Na2 SO4 (0.02 M). Moreover, the present work investigated the effectiveness of 3D electro-Fenton assisted by ultrasound known as Sono-ElectroFenton (SEF), by following a new strategy based on applying the minimum circumstances of EF and comparing its results with that of SEF under the same conditions. MO Re% for EFmin was 49.24% while SEF was 50.51%, which is considered an exiguous improvement. However, using copper foam as a working electrode in the 3D EF system for the degradation of MO was an excellent choice. Furthermore, the suggested approach is characterized by simplicity, speed, and efficiency with a high percentage of pollutant removal, in addition to being eco-friendly. [ABSTRACT FROM AUTHOR]

CoNOC with CoN (Pd)3 N (Po)1 O1 structure can efficiently catalyse the electro-Fenton reaction to generate –OH to degrade antibiotic pollutants represented by tetracyclines. [Display omitted] • Oxygen-doped Co SACs were prepared using a temperature gradient pyrolysis strategy with nitric acid oxidation method. • DFT calculations explained the excellent catalytic performance was due to the electronic modulation of Co sites by the O doping and N coordination. • TC degradation of 95 % in 120 min and mineralization efficiency of almost 90 % in 180 min were achieved in the electro-Fenton system. • The significant involvement of OH was confirmed, and the degradation pathways of TC have been analyzed and predicted. Electro-Fenton is an effective process for degrading hard-to-degrade organic pollutants, such as tetracycline (TC). However, the degradation efficiency of this process is limited by the activity and stability of the cathode catalyst. Herein, a temperature gradient pyrolysis strategy and oxidation treatment is proposed to modulate the coordination environment to prepare oxygen-doped cobalt monoatomic electrocatalysts (CoNOC). The CoNOC catalysts can achieve the selectivity of 93 % for H 2 O 2 with an electron transfer number close to 2. In the H-cell, the prepared electrocatalysts can achieve more than 100 h of H 2 O 2 production with good stability and the yield of 1.41 mol g catalyst −1 h−1 with an average Faraday efficiency (FE) of more than 88 %. The calculations indicate that the epoxy groups play a crucial role in modulating the oxygen reduction pathway. The O doping and unique N coordination of Co single-atom active sites (CoN (Pd)3 N (Po)1 O1) can effectively weaken the O 2 /OOH* interaction, thereby promoting the production of H 2 O 2. Finally, the electro-Fenton system could achieve a TC degradation rate of 94.9 % for 120 min with a mineralization efficiency of 87.8 % for 180 min, which provides a reliable option for antibiotic treatment. The significant involvement of OH in the electro-Fenton process was confirmed, and the plausible mineralization pathway for TC was proposed. [ABSTRACT FROM AUTHOR]

Antibiotics are among the most consumed drugs worldwide. These compounds enter the environment from different sources, adversely affecting human and animal health given their high persistence and stability in the environment. Conventional water and wastewater treatment processes have not been designed for removal of such materials. Thus, a suitable method should be devised for removal of these compounds. Among antibiotics, Amoxicillin (AMX) has the minimum metabolism. The aim of this research is the removal of AMX using electro-Fenton (EF) method from aqueous solutions. One of the most important disadvantages of the electro- Fenton method is its high efficiency at acidic pH, causing secondary contamination. As such, for resolving this issue, chelating agents can be used. In this study, the effects of important parameters have been examined on AMX removal efficiency including initial concentration AMX (20-120) mg/L, initial pH (3-7), current intensity (10-130) mA, and EDTA concentration (0-1) mM as chelating agent via design of experiment method. This paper introduces a simplified version of quadratic polynomial Response Surface Methodology (RSM). After analysis of variance, it was found that all examined variables were significant and the model had sufficient validity. The results showed that EDTA in addition to pH has also been influential in enhancing removal efficiency. Regarding the optimal conditions for the examined parameters, the initial concentration of AMX 24 mg/L, the current intensity 85 mA, initial pH 5.6, and EDTA dose 0.6 mM, showed 95.71% AMX removal, eventually. Also, a graphite cathode made of pencil was used for constant production of hydrogen peroxide during the process. The extent of electric energy consumption at the optimal point was obtained 0.86 KWh/m3. [ABSTRACT FROM AUTHOR]

Atomically dispersed single‐atom catalysts (SACs) on carbon supports show great promise for H2O2 electrosynthesis, but conventional wet chemistry methods using particulate carbon blacks in powder form have limited their potential as two‐electron (2e−) oxygen reduction reaction (ORR) catalysts. Here, we demonstrate high‐performance Co SACs supported on a free‐standing aligned carbon nanofiber (CNF) using electrospinning and arc plasma deposition (APD). Based on the surface oxidation treatment of aligned CNF and precise control of the deposition amount in a dry‐based APD process, we successfully form densely populated Co SACs on aligned CNF. Through experimental analyses and density functional theory calculations, we reveal that Co SAC has a Co–N2–O2 moiety with one epoxy group, leading to excellent 2e− ORR activity. Furthermore, the aligned CNF significantly improves mass transfer in flow cells compared to randomly oriented CNF, showing an overpotential reduction of 30 mV and a 1.3‐fold improvement (84.5%) in Faradaic efficiency, and finally achieves an outstanding production rate of 15.75 mol gcat−1 h−1 at 300 mA cm−2. The high‐performance Co SAC supported on well‐aligned CNF is also applied in an electro‐Fenton process, demonstrating rapid removal of methylene blue and bisphenol F due to its exceptional 2e− ORR activity. [ABSTRACT FROM AUTHOR]