Improved electrochemical oxidation of tricyclazole from aqueous solution by enhancing mass transfer in a tubular porous electrode electrocatalytic reactor

One-step synthesis of Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes used to degrade nitrobenzene

Ti/SnO2-Sb electrodes possess high catalytic activity and efficiently degrade nitrobenzene (NB); however, their low service life limits their wide application. In this study, we used one-step hydrothermal synthesis to successfully prepare Pt-Nd co-doped Ti/SnO2-Sb nanosphere electrodes. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were applied to characterize the surface morphology, microstructure, and chemical composition of the electrodes, respectively. The electrochemical activity and stability of the electrodes were characterized via linear sweep and cyclic voltammetry, electrochemical impedance spectroscopy, and an accelerated service life test; their performance for NB degradation was also studied. An appropriate amount of Pt-Nd co-doping refined the average grain size of SnO2 and formed a uniform and compact coating on the electrode surface. The oxygen evolution potential, total voltammetric charge, and electron transfer resistance of the Ti/SnO2-Sb-Nd-Pt electrodes were 1.88 V, 3.77 mC/cm2, and 11.50 Ω, respectively. Hydroxy radical was the main active radical species during the electrolytic degradation of nitrobenzene with Ti/SnO2-Sb-Nd-Pt. After Pt-Nd co-doping, the accelerated service life of the electrodes was extended from 8.0 min to 78.2 h (500 mA/cm2); although the NB degradation rate decreased from 94.1 to 80.6%, the total amount of theoretical catalytic degradation of NB in the effective working time increased from 17.4 to 8754.1 mg/cm2. These findings reveal good application potential for the electrodes and provide a reference for developing efficient and stable electrode materials.

Shifting Emphasis from Electro- to Catalytically Active Sites: Effects of Pore Size of Flow-Through Anodes on Water Purification

A flow-through anode has demonstrated high efficiency for micropollutant abatement in water purification. In addition to developing novel electrode materials, a rational design of its porous structure is crucial to achieve high electrooxidation kinetics while sustaining a low cost for flow-through operation. However, our knowledge of the relationship between the pore structure and its performance is still incomplete. Therefore, we systematically explore the effect of pore size (with a median from 4.7 to 49.4 μm) on the flow-through anode efficiency. Results showed that when the pore size was <26.7 μm, the electrooxidation kinetics was insignificantly improved, but the permeability declined dramatically. Traditional empirical evidence from hydrodynamic modeling and electrochemical tests indicated that a flow-through anode with a smaller pore size (e.g., 4.7 μm) had a high mass transfer capability and large electroactive area. However, this did not further accelerate the micropollutant removal. Combining an overpotential distribution model and an imprinting method has revealed that the reactivity of a flow-through anode is related to the catalytically active volume/sites. The rapid overpotential decay as a function of depth in the anode would offset the merits arising from a small pore size. Herein, we demonstrate an optimal pore size distribution (∼20 μm) of typical flow-through anodes to maximize the process performance at a low energy cost, providing insights into the design of advanced flow-through anodes in water purification applications.

Unveiling the spatially confined oxidation processes in reactive electrochemical membranes

Electrocatalytic oxidation offers opportunities for sustainable environmental remediation, but it is often hampered by the slow mass transfer and short lives of electro-generated radicals. Here, we achieve a four times higher kinetic constant (18.9 min-1) for the oxidation of 4-chlorophenol on the reactive electrochemical membrane by reducing the pore size from 105 to 7 μm, with the predominate mechanism shifting from hydroxyl radical oxidation to direct electron transfer. More interestingly, such an enhancement effect is largely dependent on the molecular structure and its sensitivity to the direct electron transfer process. The spatial distributions of reactant and hydroxyl radicals are visualized via multiphysics simulation, revealing the compressed diffusion layer and restricted hydroxyl radical generation in the microchannels. This study demonstrates that both the reaction kinetics and the electron transfer pathway can be effectively regulated by the spatial confinement effect, which sheds light on the design of cost-effective electrochemical platforms for water purification and chemical synthesis.

An extra-chelator-free fenton process assisted by electrocatalytic-induced in-situ pollutant carboxylation for target refractory organic efficient treatment in chemical-industrial wastewater

For traditional Fenton processes, the quenching behavior of radical contenders (e.g., most aliphatic hydrocarbons) on hydroxyl radicals (·OH) usually hinders the removal of target refractory pollutants (aromatic/heterocyclic hydrocarbons) in chemical industrial wastewater, leading to excess energy consumption. Herein, we proposed an electrocatalytic-assisted chelation-Fenton (EACF) process, with no extra-chelator addition, to significantly enhance target refractory pollutant (pyrazole as a representative) removal under high ·OH contender (glyoxal) levels. Experiments and theoretical calculations proved that superoxide radical (·O₂^-) and anodic direct electron transfer (DET) effectively converted the strong ·OH-quenching substance (glyoxal) to a weak radical competitor (oxalate) during the electrocatalytic oxidation process, promoting Fe²⁺ chelation and therefore increasing radical utilization for pyrazole degradation (reached maximum of ∼43-fold value upon traditional Fenton), which appeared more obviously in neutral/alkaline Fenton conditions. For actual pharmaceutical tailwater treatment, the EACF achieved 2-folds higher oriented-oxidation capability and ∼78% lower operation cost per pyrazole removal than the traditional Fenton process, demonstrating promising potential for future practical applications.

Coupling anodic and cathodic reactions using an electrocatalytic dual-membrane system actuates ultra-efficient degradation with regulable mechanisms

The versatile reaction possibilities arising from the interaction between the anodic and cathodic reactions naturally contained in electrocatalytic membrane filtration (EMF) systems are of great valuable in meeting the current complex water treatment requirements. But currently, most studies only focus on half-cell reactions with a single electrocatalytic membrane, which limits the research progress of the EMF technology. Here we report a coupling strategy that utilizes the interaction between the anodic and cathodic reactions to actuate ultra-efficient degradation performance with regulable reaction mechanisms. An electrocatalytic dual-membrane filtration (EDMF) system was established. Six typical configurations of the EDMF system were set up and systematically investigated by adjusting the electrode distance and filtration sequence. Based on the obtained results of degradation performance and mechanisms, a regulation strategy which enabled flexible tuning of direct nonradical oxidation (e.g., h⁺) and indirect oxidation (e.g., ¹O₂, ·OH, HO₂·, O₂·^-, etc.) was proposed. In particular, cathodic reactions were found to adversely affect the anodic reactions at the relatively short electrode distance of 0.9 mm. Anodic reactions could inhibit the generation of ¹O₂ at short distance of 0.9 mm but promote its generation at long distances of 9 and 17 mm. The A-C_0.9 configuration achieved the highest degradation performance, while the C-A_9 configuration was revealed to be much more conducive to ¹O₂ production. Overall, our findings demonstrate the versatility and tunability of the reaction mechanism and performance of the EDMF system due to the flexible coupling of the anodic and cathodic reactions, which potentially lays a foundation for future development of ultra-efficient mechanism-adjustable electrocatalysis technologies.

Membrane Fouling and Electrochemical Regeneration at a PbO2-Reactive Electrochemical Membrane: Study on Experiment and Mechanism

Membrane fouling and regeneration are the key issues for the application of membrane separation (MS) technology. Reactive electrochemical membranes (REMs) exhibited high, stable permeate flux and the function of chemical-free electrochemical regeneration. This study fabricated a micro-filtration REM characterized by a PbO₂ layer (PbO₂-REM) to investigate the electro-triggered anti-fouling and regeneration progress within REMs. The PbO₂-REM exhibited a three-dimensional porous structure with a few branch-like micro-pores. The PbO₂-REM could alleviate Humic acid (HA) and Bisphenol A (BPA) fouling through electrochemical degradation combined with bubble migration, which achieved the best anti-fouling performance at current density of 4 mA cm^-2 with 99.2% BPA removal. Regeneration in the electro-backwash (e-BW) mode was found as eight times that in the forward wash and full flux recovery was achieved at a current density of 3 mA cm^-2. EIS and simulation study also confirmed complete regeneration by e-BW, which was ascribed to the air-water wash formed by bubble migration and flow. Repeated regeneration tests showed that PbO₂-REM was stable for more than five cycles, indicating its high durability for practical uses. Mechanism analysis assisted by finite element simulation illustrated that the high catalytic PbO₂ layer plays an important role in antifouling and regeneration.

Recent advances in electrocatalytic membrane for the removal of micropollutants from water and wastewater

The increasing occurrence of micropollutants in water and wastewater threatens human health and ecological security. Electrocatalytic membrane (EM), a new hybrid water treatment platform that integrates membrane separation with electrochemical technologies, has attracted extensive attention in the removal of micropollutants from water and wastewater in the past decade. Here, we systematically review the recent advances of EM for micropollutant removal from water and wastewater. The mechanisms of the EM for micropollutant removal are first introduced. Afterwards, the related membrane materials and operating conditions of the EM are summarized and analyzed. Lastly, the challenges and future prospects of the EM in research and applications are also discussed, aiming at a more efficient removal of micropollutants from water and wastewater.

Insight into the rapid elimination of low-concentration antibiotics from natural waters using tandem multilevel reactive electrochemical membranes: Role of direct electron transfer and hydroxyl radical oxidation

Herein, we reported a tandem multilevel reactive electrochemical membrane (REM) system was promising for the rapid and complete removal of trace antibiotics from natural waters. Results indicate that a four-stage REM module-in-series system achieved steady over 98% removal of model antibiotic norfloxacin (NOR, 100 μg·L^-1) from wastewater treatment plant final effluent and surface water with a residence time of 5.4 s, and the electric energy consumption was only around 0.007-0.011 kWh·m^-3. As for the oxidation mechanism, direct electron transfer (DET) oxidation process played an important role in NOR rapid oxidation, enabling the REM system to tolerate various ^•OH scavenges in natural waters, including natural organic matters, Cl^- and HCO₃^-, even at very high concentration levels. Meanwhile, ^•OH-mediated indirect oxidation process promotes the oxidation and mineralization of NOR. Although the DET-dominated oxidation mechanism makes the REM system cannot achieve the complete mineralization of NOR with residence times of few seconds, the antibacterial activity from NOR was completely eliminated. This REM system featured effective removal performance of trace contaminants with low energy cost and was tolerant to complex waster matrix, suggesting that it could be a powerful supplementary step for wastewater/water treatment.

Electrochemical oxidation of reverse osmosis concentrates using macroporous Ti-ENTA/SnO2-Sb flow-through anode: Degradation performance, energy efficiency and toxicity assessment

Due to poor mass transfer performance and high energy consumption of the traditional electrochemical flow-by mode, this study developed a high-efficiency electrochemical oxidation system in flow-through mode based on three-dimensional macroporous enhanced TiO₂ nanotube array/SnO₂-Sb (MP-Ti-ENTA/SnO₂-Sb) anode. The effects of initial pH, current density and flow rate on the COD degradation of reverse osmosis concentrates (ROCs) from reclaimed wastewater plant were investigated. Besides, the energy efficiency, biodegradability and acute biotoxicity were studied during electrochemical flow-through process. Compared with the flow-by mode, the flow-through mode based on the MP-Ti-ENTA/SnO₂-Sb anode had a COD removal rate of 0.38 mg min^-1 (current density: 5 mA cm^-2) and an electrical efficiency per order (EE/O) of 5.3 kW h m^-3. The three-dimensional fluorescence spectrum showed that the fulvic acids, humic acids and soluble microbial metabolites of ROCs could be effectively removed by the flow-through anode. In addition, the luminescence inhibition rate of the effluent was 22.4 %, indicating that the acute biotoxicity was reduced by more than 40 %. The electrochemical flow-through process of ROCs treatment required relatively low energy consumption without extra chemical agent addition, showing a broader application prospect.

Electro-catalytic membrane reactors for the degradation of organic pollutants – a review

Electro-catalytic membrane reactor exhibiting electro-oxidation degradation of organic pollutants on anodic membrane.

CFD simulation of mass transfer in electrochemical reactor with mesh cathode for higher phenol degradation

Cathode, where electro-catalytic oxidation barely took place, could exert a significant influence on electro-catalytic efficiency, whereas little investigation has been focused on this effect. In this study, the effect of cathode configuration on electro-catalytic activities was investigated with phenol as model pollutant, and the mechanism was revealed from the perspective of mass transfer with computational fluid dynamics (CFD) simulation. Compared with the planar Ti cathode, the electro-catalytic reactor with mesh Ti exhibited 1.21-1.26 times faster phenol degradation rate under various testing inlet flow rates. CFD simulation revealed the higher velocity distribution both in the reactor and on anode surface when meshed Ti cathode was used, which benefited faster fluid flow so that the pollutant transfer was accelerate especially at higher inlet flow rate. Excellent agreement of mass transfer between CFD simulation and experimental analysis was achieved, the mass transfer coefficient with mesh Ti was 1.40-1.55 times of the case with planar cathode under various inlet flow rates. The enhanced mass transfer performance was mainly ascribed to the rhombic pores of mesh cathode where hydrogen bubbles generated on would escape timely and randomly at various directions, leading to the disturbance of fluid flow around the anode. This study highlighted mesh cathode played a key role in improving pollutant degradation, and CFD, as a versatile and convenient tool to analyze the hydrodynamic behavior of electro-catalytic reactor, showed a strong persuasion to guide the optimization of electrode configuration.

Using modulated current for energy minimization in the electrochemical treatment of effluents containing organic pollutants

Anodic oxidation of recalcitrant organic compounds suffers from loss of efficiency as the concentration decreases, leading to high energy consumption. Here, we propose a modulated current (MC) technique to control and maintain the applied current as close as possible to its limiting value throughout the electrolysis, thus ensuring high mineralization current efficiency. The efficacy of this technique was first validated for caffeic acid (CA) electrooxidation using a boron-doped diamond (BDD) anode and was then confirmed for the degradation of a wastewater containing phenolic compounds from wet coffee processing. Combining MC and constant current (CC) operation for CA electrolysis resulted in a substantial reduction of the specific energy consumption from 256 to 52.4 kWh kg^-1 TOC, due to improvement of the mineralization current efficiency from 17.9 to 77.1%. The MC+CC technique was also successful in reducing the energy consumption for a real coffee processing wastewater mineralization, demonstrating its suitability as a simple and effective tool that can be used to reduce the energy costs in electrochemical treatment of effluents containing organic pollutants.

Membrane Separation Coupled with Electrochemical Advanced Oxidation Processes for Organic Wastewater Treatment: A Short Review

Research on the coupling of membrane separation (MS) and electrochemical advanced oxidation processes (EAOPs) has been a hot area in water pollution control for decades. This coupling aims to greatly improve water quality and focuses on the challenges in practical application to provide a promising solution to water shortage problems. This article provides a summary of the coupling configurations of MS and EAOPs, including two-stage and one-pot processes. The two-stage process is a combination of MS and EAOPs where one process acts as a pretreatment for the other. Membrane fouling is reduced when setting EAOPs before MS, while mass transfer is promoted when placing EAOPs after MS. A one-pot process is a kind of integration of two technologies. The anode or cathode of the EAOPs is fabricated from porous materials to function as a membrane electrode; thus, pollutants are concurrently separated and degraded. The advantages of enhanced mass transfer and the enlarged electroactive area suggest that this process has excellent performance at a low current input, leading to much lower energy consumption. The reported conclusions illustrate that the coupling of MS and EAOPs is highly applicable and may be widely employed in wastewater treatment in the future.

Development of a highly efficient electrochemical flow-through anode based on inner in-site enhanced TiO2-nanotubes array

This paper reports on the development of macroporous flow-through anodes. The anodes comprised an enhanced TiO₂ nanotube array (ENTA) that was grown on three macroporous titanium substrates (MP-Ti) with nominal pore sizes of 10, 20, and 50 µm. The ENTA was then covered with SnO₂-Sb₂O₃. We refer to this anode as the MP-Ti-ENTA/SnO₂-Sb₂O₃ anode. The morphology, pore structure, and electrochemical properties of the anode were characterized. Compared with the traditional NTA layer, we found that the MP-Ti-ENTA/SnO₂-Sb₂O₃ anode has a service lifetime that was 1.56 times larger than that of MP-Ti-NTA/SnO₂-Sb₂O₃. We used 2-methyl-4-isothiazolin-3-one (MIT), a common biocide, as the target pollutant. We evaluated the impact of the operating parameters on energy efficiency and the oxidation rate of MIT. Furthermore, the apparent rate constants were 0.38, 1.63, and 1.24 min^-1 for the 10, 20, and 50 μm nominal pore sizes of the MP-Ti substrates, respectively, demonstrating the different coating-loading mechanisms for the porous substrate. We found that hydroxyl radicals were the dominant species in the MIT oxidation in the HO radical scavenging experiments. The radical and nonradical oxidation contributions to the MIT degradation for different current densities were quantitatively determined as 72.1%-74.8% and 25.2%-27.9%, respectively. Finally, we summarized the oxidation performance for MIT destruction for (1) the published literature on various advanced oxidation technologies, (2) the published literature on various anodes, and (3) our flow-by and -through anodes. Accordingly, we found that our flow-through anode has a much lower electrical efficiency per order value (0.58 kWh m^-3) than the flow-by anodes (6.85 kWh m^-3).

Use of a novel coupled-oxidation tubular reactor (COTR)/ NTP-DBD catalytic plasma in a synergistic electro-catalysis system for odorous mercaptans degradation

In this work, a novel coupled-oxidation tubular reactor (COTR)/non-thermal dielectric barrier discharge (NTP-DBD) catalytic plasma in a synergistic electro-catalysis system was investigated for odorous mercaptans decomposition. In order to enhance the degradation efficiency of electro-oxidation, a novel enhanced Ti/PbO₂ electro-catalytic tubular reactor prepared by using flow dynamic electrodeposition was designed and applied as pretreatment process for CH₃SNa wastewater. The results indicated that the optimal condition was 7 mA cm^-2 of current density, 10 g L^-1 of initial concentration of CH₃SNa, 9.0 of pH and 5.0 g L^-1 of electrolyte concentration. Addition of Fe²⁺ and H₂O₂ and mechanism of COTR system were first put forward. The target species CH₃SNa were removed over 90% by this process. In order to treat the CH₃SH effusion which was co-produced with CH₃SNa aqueous solution, the technology of NTP-DBD catalytic plasma reactor followed by a chemical absorption has been developed. MSH could be removed over 95% under the condition of 2 s of residence time, 15 kV of output voltage with oxygen concentration of 9%. Moreover, the synthetic Ni-doped AC catalyst had the best performance under 0.7 mmol g^-1 of nickel loading. The conclusion was the energetic electrons generated in the DBD reactor played a key role on the removal of MSH, and the major decomposition products of MSH were detected as CH₃SSCH₃, SO₂ and NO₂. Moreover, the gaseous products in the plasma exhaust could be absorbed and fixed by the subsequent aqueous NaOH solution.

Electro-oxidation of organic pollutants by reactive electrochemical membranes

Electro-oxidation processes are promising options for the removal of organic pollutants from water. The major appeal of these technologies is the possibility to avoid the addition of chemical reagents. However, a major limitation is associated with slow mass transfer that reduces the efficiency and hinders the potential for large-scale application of these technologies. Therefore, improving the reactor configuration is currently one of the most important areas for research and development. The recent development of a reactive electrochemical membrane (REM) as a flow-through electrode has proven to be a breakthrough innovation, leading to both high electrochemically active surface area and convection-enhanced mass transport of pollutants. This review summarizes the current state of the art on REMs for the electro-oxidation of organic compounds by anodic oxidation. Specific focuses on the electroactive surface area, mass transport, reactivity, fouling and stability of REMs are included. Recent advances in the development of sub-stoichiometric titanium oxide REMs as anodes have been made. These electrodes possess high electrical conductivity, reactivity (generation of ^•OH), chemical/electrochemical stability, and suitable pore structure that allows for efficient mass transport. Further development of REMs strongly relies on the development of materials with suitable physico-chemical characteristics that produce electrodes with efficient mass transport properties, high electroactive surface area, high reactivity and long-term stability.

Electrochemical treatment of flutriafol wastewater using a novel 3D macroporous PbO2 filter: Operating parameters, mechanism and toxicity assessment

In order to break the high operating cost bottleneck of electrochemical treatment of aqueous flutriafol (FTF), an emerging fungicide, a novel three-dimensional ordered macroporous PbO₂ (3DOM-PbO₂) filter was designed to facilitate mass transfer. The effects of operating parameters, including current density, flow rate and initial concentration on FTF electrooxidation performance were investigated using conventional flat Ti/PbO₂ (F-Ti/PbO₂) and 3DOM-PbO₂ filters, with primary objective being the development of appropriate parameters for FTF treatment. The results indicated that the FTF removal efficiency on 3DOM-PbO₂ filter was improved by 2.8 times compared to that on F-Ti/PbO₂ at 5 mA cm^-2, 10 ml s^-1 and 100 mg L^-1 FTF. The corresponding electrical energy consumption was reduced by 2.7 times, ` TOC removal and mineralization current efficiency were enhanced by 4.9 and 4.8 times, respectively. Furthermore, aromatic intermediates, nitrogenous compounds and carboxylic acids were identified as main byproducts using experimental method combined with quantum chemical calculations. Then, a possible pathway of FTF degradation on 3DOM-PbO₂ was proposed. Finally, the acute toxicity results showed that toxicity of the byproducts first increases and then decreases through the proposed route. LC_50,48 h value of FTF wastewater increased 35%-70% on the 3DOM-PbO₂ filter, indicating a significant biodegradability enhancement.

Current advances and trends in electro-Fenton process using heterogeneous catalysts - A review

Over the last decades, advanced oxidation processes have often been used alone, or combined with other techniques, for remediation of ground and surface water pollutants. The application of heterogeneous catalysis to electrochemical advanced oxidation processes is especially useful due to its efficiency and environmental safety. Among those processes, electro-Fenton stands out as the one in which heterogeneous catalysis has been broadly applied. Thus, this review has introduced an up-to-date collation of the current knowledge of the heterogeneous electro-Fenton process, highlighting recent advances in the use of different catalysts such as iron minerals (pyrite, magnetite or goethite), prepared catalysts by the load of metals in inorganic and organic materials, nanoparticles, and the inclusion of catalysts on the cathode. The effects of physical-chemical parameters as well as the mechanisms involved are critically assessed. Finally, although the utilization of this process to remediation of wastewater overwhelmingly outnumber other utilities, several applications have been described in the context of regeneration of adsorbent or the remediation of soils as clear examples of the feasibility of the electro-Fenton process to solve different environmental problems.

Hydrophobic networked PbO2 electrode for electrochemical oxidation of paracetamol drug and degradation mechanism kinetics

A hydrophobic networked PbO₂ electrode was deposited on mesh titanium substrate and utilized for the electrochemical elimination towards paracetamol drug. Three dimensional growth mechanism of PbO₂ layer provided more loading capacity of active materials and network structure greatly reduced the mass transfer for the electrochemical degradation. The active electrochemical surface area based on voltammetric charge quantity of networked PbO₂ electrode is about 2.1 times for traditional PbO₂ electrode while lower charge transfer resistance (6.78 Ω cm²) could be achieved on networked PbO₂ electrode. The electrochemical incineration kinetics of paracetamol drug followed a pseudo first-order behavior and the corresponding rate constant were 0.354, 0.658 and 0.880 h^-1 for traditional, networked PbO₂ and boron doped diamond electrode. Higher electrochemical elimination kinetics could be achieved on networked PbO₂ electrode and the performance can be equal to boron doped diamond electrode in result. Based on the quantification of reactive oxidants (hydroxyl radicals), the utilization rate of hydroxyl radicals could reach as high as 90% on networked PbO₂ electrode. The enhancement of excellent electrochemical oxidation capacity towards paracetamol drug was related to the properties of higher loading capacity, enhanced mass transfer and hydrophobic surface. The possible degradation mechanism and pathway of paracetamol on networked PbO₂ electrode were proposed in details accordingly based on the intermediate products.

Engineering Interface with One-Dimensional Co3O4 Nanostructure in Catalytic Membrane Electrode: Toward an Advanced Electrocatalyst for Alcohol Oxidation

Electrochemical oxidation has attracted vast interest as a promising alternative to traditional chemical processes in fine chemical synthesis owing to its fast and sustainable features. An electrocatalytic membrane reactor (ECMR) with a three-dimensional (3D) electrode has been successfully designed for the selective oxidation of alcohols with high current efficiency to the corresponding acids or ketones. The anode electrode was fabricated by the in situ loading of one-dimensional (1D) Co₃O₄ nanowires (NWs) on the conductive porous Ti membrane (Co₃O₄ NWs/Ti) via the combination of a facile hydrothermal synthesis and subsequent thermal treatment. The electrocatalytic oxidation (ECO) results of alcohols exhibited superior catalytic performance with a higher current efficiency on the Co₃O₄ NWs/Ti membrane compared with those of Co₃O₄ nanoparticles on the Ti membrane (Co₃O₄ NPs/Ti). Even under low reaction temperatures such as 0 °C, it still displayed a very high ECO activity for alcohol oxidation in the ECMR. For example, >99% conversion and 92% selectivity toward benzoic acid were obtained for the benzyl alcohol electrooxidation. The electrode is particularly effective for the cyclohexanol oxidation, and a selectivity of >99% to cyclohexanone was achieved at 0 °C, higher than most reported noble-metal catalysts under the aerobic reaction conditions. The extraordinary electrocatalytic performance of the 3D Co₃O₄ NWs/Ti membrane electrode demonstrates the significant influence of morphology effect and engineering interfaces in membrane electrodes on the electrocatalytic activity and charge transfer process of nanocatalysts. Our results propose that similar membrane electrodes serve as versatile platforms for the applications of 1D nanomaterials, porous electrodes, and ECMRs.

Pesticide tailwater deeply treated by tubular porous electrode reactor (TPER): Purpose for discharging and cost saving

Pesticide tailwater often contains residual and toxic contaminants of triazole fungicides (TFs) due to their poor biodegradability which will do great harm to local aquatic systems. For this case, a novel electrochemical reactor (TPER) equipped a tubular porous RuO₂-Sb₂O₅-SnO₂ electrode was assembled and then employed to deeply treat pesticide tailwater. Characterizations of the electrode studied by SEM, EDS and XRD analysis indicated that it owns a porous structure and a compact and crack-free surface. Influence of the porous structure on electrochemical property was examined by cyclic voltammetry and normal pulse voltammetry. The results indicated that porous structure can not only enlarge electrochemical active area but also increase mass transfer efficiency by 5.7-fold in flow-through mode compared with batch mode. Furthermore, the optimal operating conditions of TPER were flow rate of 250 mL min^-1 and current density of 4 mA cm^-2. After 1.5 h treatment under these conditions, Tz, TC and PPC were removed by 98.9%, 99.0% and 98.4% respectively, while 81.9% of COD was also removed. Additionally, the microbial content was dropped to 0 CFU mL^-1 and fecal coliform was lower than 2 MPN (100 mL)^-1. All results demonstrated that the treated tailwater has met the Class 1 of National Discharge Standard of China. Especially, operating cost of TPER was only $ 0.33 per ton. The excellent performance together with the low cost indicated that TPER is a promising option for depth treatment of industrial tailwater.

Preparation and characterization of a TiO2-NT/SnO2–Sb tubular porous electrode with long service lifetime for wastewater treatment process

We have studied the formation process of a novel TiO₂-NTs/SnO₂–Sb tubular porous electrode with a long service lifetime for the wastewater treatment process.

A hydrophobic three-dimensionally networked boron-doped diamond electrode towards electrochemical oxidation

Three-dimensionally networked boron-doped diamond with a microstructure and enhanced mass transfer showed excellent electro-oxidation ability towards contaminants.