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Water flooding in the microporous cathode is poisonous but inevitable for oxygen reduction reaction (ORR) in electro-Fenton (EF) processes. To meet this challenge, a facile modification was reported to stabilize performance of cathode through the infiltration process, which selecting superior CB-PTFE electrode as backbone and dimethyl silicon oil (DMS) as maturation layer. Characterized by FE-SEM, EDS, BET, XRD, the matured cathode was proved to be wrapped uniformly by DMS. Electrochemical performances of cathodes were evaluated by CA, CV, EIS and CP measurements in oxygen “starvation” condition. These results proved that the maturation layer improved the electrocatalysis on 2 e − ORR, the service lifetime from 1.68 h to 18.34 h, the working range of current density from 70 to 110 A m−2 and reduced the oxygen diffusion resistance from 74.23 to 8.07 Ω. Besides, H2O2 generation and oxygen utilization of 2%DMS cathode respectively reached 126.7 mg L−1 and 83.49% in 60 min, which were rarely influenced by pH and aeration rate even after water flooding process. 2%DMS layer served as the accelerated oxygen transport channel can explain the enhanced oxygen transport. The simulated contaminated solution containing a fungicide-flutriafol (FTF) was obtained 100% removal in about 40 min and 48.88% TOC removal in 2 h. The lifetime tests revealed much more stable decay of FTF under the broader operational condition.

In order to develop an electrochemical technology with low-energy consumption for water treatment applications, we fabricated a novel reactive electrochemical membrane (REM) operated in cross-flow filtration mode. The REM with three-dimensional ordered macroporous PbO2 (3DEM-PbO2) film was synthesized via templated deposition that was based on a porous Ti substrate. Compared to conventional flat Ti/PbO2 (F-Ti/PbO2) electrode, the 3DEM-PbO2 possessed larger specific surface area (38.89 m2 g−1), higher oxygen evolution potential (OEP, 1.9 V), larger Voltammetric charge (238 mC cm−2) and smaller electron transfer resistance (1.43 Ω). Furthermore, advection-enhanced mass transfer was obtained when the 3DEM-PbO2 REM is operated in an electrochemical filtration reactor (EFR), relative to a traditional batch reactor (BR). The electrochemical mineralization experiments with flutriafol (FTF) demonstrated that the 3DEM-PbO2 REM operated in the EFR was active for FTF and TOC removal at a low current density of 5 mA cm−2. The oxidation current efficiency of REM operated in a EFR was much higher than that of conventional electrochemical system, and the corresponding energy consumption was lower (0.0505 kWh g−1 FTF, at FTF removal of 75%). The hydroxyl radicals (·OH) production and its utilization rate of the REM was significantly improved, resulting from a combination of the strong catalytic activity of 3DEM-PbO2 and the enhanced mass transfer by filtration mode. Furthermore, computational fluid dynamics (CFD) method was carried out to help explain the improvement of oxidation performance with 3DEM-PbO2 REM in a EFR. Eventually, the electrocatalysis experiments of practical wastewater demonstrated the extreme promise of 3DEM-PbO2 REM for tailwater advanced treatment applications.

In order to develop a highly efficient anode material for recalcitrant phenol degradation in bioelectrochemical system (BES), fabrication of polypyrrole (PPy)/β-MnO2 composite onto graphite felt (GF) electrode through facile one-step electrodeposition was investigated in this study. The successful coating of PPy/β-MnO2 onto GF surface was verified by scanning electron microscopy, Raman spectrum and XPS. The improved electrochemical property of the GF electrode modified by PPy/β-MnO2 was confirmed by cyclic voltammetry analysis, chronoamperometric and electrochemical impedance spectra. The application of PPy/β-MnO2 modified GF electrodes in BES notarized the superior degradation performance towards phenol. Shorter startup time, higher mineralization efficiency and improved bacteria adhesion was achieved in BES using PPy/β-MnO2 modified GF as anode. Coulombic efficiencies of 17.3 ± 0.5% in BES using PPy/β-MnO2 modified GF as anode was much higher than those in BES using PPy modified GF and blank GF as anode, which were as low as 12.1 ± 2.4% and 6.6 ± 1.3%, respectively. The key role of MnO2 and possible degradation pathway involved in phenol degradation was further proposed. The milder fabrication condition, improved electrochemical activity and increased phenol degradation efficiency suggest that PPy/β-MnO2/GF has a promising future in BES application for recalcitrant phenol catalytic degradation.

Flutriafol is one of the widely used triazole fungicides in global pesticides market, and its degradation mechanisms are important to develop powerful technologies to remove it. Insight into the kinetics and mechanisms of ·OH-mediated mineralization of flutriafol have been obtained using quantum chemical calculation and electrochemical experiment methods. The complete ·OH-mediated degradation pathway of flutriafol was proposed by density functional theory (DFT) simulation and the potential energy surface was mapped out for possible reactions. On the basis of DFT calculations, the optimal ·OH-mediated mineralization mechanism of flutriafol was revealed, and a series of intermediates were observed accumulated in the degradation process, most significance among which were (2-fluorophenyl) (4-fluorophenyl)-Methanone, phenol, dihydroxybenzenes, benzoquinones, muconic acids, maleic acids, oxalic acids and formic acid. To give deeper insight into the ·OH-mediated reaction mechanism, the electrostatic potential (ESP) and average local ionization energy (ALIE) analysis were conducted for o-benzoquinone and p-benzoquinone. The proposed mechanism was further validated by electrochemical experiments at TiO2-NTs/SnO2-Sb/PbO2 anode. The main intermediates were identified and quantified by experimental method, indicating that the proposed ·OH-mediated degradation mechanism derived from DFT calculations was feasible. These detailed findings could be instrumental for a comprehensive understanding of the ·OH-mediated mineralization mechanism of flutriafol and the similar contaminants.

A novel tubular porous electrode electrocatalytic reactor was employed to undertake electrochemical treatment of actual anticancer drugs wastewater containing 5-Fluoro-2-Methoxypyrimidine. Effects of operating parameters on the performance of the reactor were studied with the discussion of energy consumption. The results indicated that the optimal condition was flow rate of 0.31 L min−1, pH value of 5.0, current density of 5 mA cm−2 and without supporting electrolyte. In addition, the degradation intermediates and final products of 5-Fluoro-2-Methoxypyrimidine were analyzed by GC-MS and IC system. A pathway for the electrochemical degradation was proposed as well by quantum chemical calculation using DFT method. After treatment in the reactor, COD and 5-Fluoro-2-Methoxypyrimidine of the wastewater were removed by 84.1% and 100%. Particularly, the BOD5/COD value and EC50,48h value of wastewater were increased from 0.14 and 16.4% to 0.53 and 51.2% respectively, indicating a great biodegradability enhancement. Besides, the electric energy consumption and operating cost of the reactor were only 1.5 kWh kg−1 COD and $ 0.78 per ton, lower than the other conventional electrochemical reactors. The excellent performance as well as the low energy consumption of the electrocatalytic reactor confirmed that electrochemical oxidation is highly applicable for the treatment of anticancer drugs wastewater.

In order to realize simultaneous removal of pyridine and denitrification, an integrated bioelectro-photocatalytic system (IBPS) equipped with N-doped graphene/α-Fe2O3 modified graphite felt (GF) photoanode and GF biocathode was constructed and operated in ON-OFF illumination mode. Compared to α-Fe2O3 modified GF electrode, N-doped graphene/α-Fe2O3 modified photoanode showed superior stability, photo-electrochemical and catalytic activity owing to the excellent electron transporting properties of N-doped graphene and unique structure of N-doped graphene/α-Fe2O3 composite. In IBPS, ammonia produced from pyridine photocatalytic degradation diffused from anode to biocathode through the cation-exchange membrane. Simultaneous nitrification and denitrification were realized in the biocathode chamber under limited dissolved oxygen. At the same time, the harvested photo-electrons derived from photoanode were delivered to the biocathode via an external circuit for enhanced denitrification. Complete removal of pyridine and high TOC removal efficiency of 85.90 ± 5.48% in the anode and complete denitrification in the biocathode after four ON-OFF cycles (96 h) reaction were achieved. Furthermore, the underlying mechanism for the enhanced removal of pyridine and denitrification was proposed preliminarily. This integrated reactor synergically utilized photoenergy, electrical energy and bioenergy for removal of pyridine and denitrification, showing a promising future in designing new systems for water environmental remediation from solar energy.

In order to develop an environmental benign method for the modification of graphite felt (GF) electrode, laccase-catalyzed electrochemical fabrication of polyaniline/graphene oxide (PANi/GO) composite at facile pH condition was investigated in this study. At the presence of laccase, aniline polymerization was remarkable at pH as high as 3.6, which was unfavorable for traditional chemical and electrochemical polymerization. The successful coating of PANi/GO on the electrode surface at the presence of laccase was verified by contact angle, scanning electron microscopy, Fourier transform infrared spectrum and Raman spectrum. The improved electrochemical property of the GF modified by PANi/GO at the presence of laccase (Lac.-PANi/GO/GF) was confirmed by cyclic voltammetry (CV) analysis. The application of the modified electrodes in the bioelectrochemical system (BES) notarized the superior electrogenesis performance of Lac.-PANi/GO/GF. Much higher power density, smaller internal resistance and shorter start-up time was achieved in the BES using Lac.-PANi/GO/GF as the anode. The maximum power density of 755.95 mW m −2 in BES using Lac.-PANi/GO/GF as anode was much higher than that in BES using PANi/GO/GF and blank GF as anode, which were as low as 364.59 and 100.43 mW m −2 , respectively. The milder react condition, improved electrochemical activity and biocompatibility suggested that Lac./PANi/GO/GF electrode had a promising future in BES application.

Application of commercial electrochemical oxidation reactor for industry discharge water was limited by the inefficient mass transfer of molecule. For this case, a functional electrocatalytic reactor was designed to enhance the mass transfer of the electrochemical oxidation. The reactor is composed of a tubular porous Ti-RuO 2 electrode and a stainless steel tube. The electrode was fabricated by loading an electrocatalytic membrane of RuO 2 on a porous Ti tube. Characterization of the electrode was analyzed by FE-SEM, XRD, XPS and bubble point method. The results show that the electrode consisted of micropore structure which pore size and porosity were 0.98 μm and 27%, respectively. Further, the results of cyclic voltammetry method have proved that porous electrode has larger electrochemical surface area than plate electrode with the same geometrical area. In addition, the steady-state of chronoamperometry measurements by the reactor was as twice as that of plate electrode, indicating a significant enhancement of mass transfer. Electrochemical oxidation of tricyclazole was investigated with reactor and plate electrode under different initial concentration and current density. By the comparison with plate electrode, the reactor has higher removal rate and current efficiency. The high performance of electrocatalytic reactor based on the tubular porous Ti-RuO 2 electrode in the electrochemical oxidation is mainly attributed to mass transfer enhancement via the pump and larger electrochemical surface area due to porous structure.

Triazole fungicides (TFs) are toxic and bio-refractory contaminants widely spread in environment. This study investigated electrochemical degradation of TFs in aqueous solution at TiO2-NTs/SnO2-Sb/PbO2 anode with particular attention to the effect of molecular structure. Three TFs with triazole ring in one biologically treated water including tricyclazole (TC), 1H-1,2,4-triazole (Tz) and propiconazole (PPC) were selected as the target compounds. Results of bulk electrolysis showed that degradation of all TFs was fit to a pseudo first-order equation. The three compounds were degraded with the following sequence: PPC > TC> Tz in terms of their rates of oxidation. Quantum chemical calculation using the density function theory (DFT) method was combined with experimental results to describe the degradation sequence of TFs. Atom charge was calculated by DFT method and active sites of TFs were identified respectively. Analysis of intermediates by GC-MS and LC-(ESI)-MS/MS showed agreement with calculation results. In addition, the acute toxicity of TC and PPC treated solution significantly decreased after treatment by electrochemical oxidation.

The research on electrochemical oxidation of dinitrotoluene (DNT) wastewater assisted by Sn–Sb–Ag-modified ceramic particulates (SCP) was studied. With the assistance of SCP, the enhancement of COD removal, decrease of energy consumption and improvement in biodegradability of the wastewater were very obvious. The apparent rate constants for the removals of absorbance at 358 nm (Abs358 nm), concentration of DNT and total organic carbon (TOC) were also greatly enhanced by SCP. Mechanism of enhanced electrochemical oxidation by SCP has been evaluated from the accumulated hydroxyl radical concentration. In situ generation of the strong oxidizing agents by SCP in the electrochemical system contributed to the enhanced electrochemical oxidation performance towards organic compounds.