Electrochemical Oxidation Technology Research Articles

Degradation of levofloxacin from antibiotic wastewater by pulse electrochemical oxidation with BDD electrode

Antibiotic-containing wastewater is a typical biochemical refractory organic wastewater and general treatment methods cannot effectively and quickly degrade the antibiotic molecules. In this study, a novel boron-doped diamond (BDD) pulse electrochemical oxidation (PEO) technology was proposed for the efficient removal of levofloxacin (LFXN) from wastewater. The effects of current density (j), initial pH (pH0), frequency (f), electrolyte types and initial concentration (c0(LFXN)) on the degradation of LFXN were systematically investigated. The degradation kinetics under four different processes have also been studied. The possible degradation mechanism of LFXN was proposed by Density functional theory calculation and analysis of degradation intermediates. The results showed that under the optimal parameters, the COD removal efficiency (η(COD)) was 94.4% and the energy consumption (EEC) was 81.43 kWh·m−3 at t = 120 min. The degradation of LFXN at pH = 2.8/c(H2O2) followed pseudo-first-order kinetics. The apparent rate constant was 1.33 × 10−2 min−1, which was much higher than other processes. The degradation rate of LFXN was as follows: pH = 2.8/c(H2O2) > pH = 2.8 > pH = 7/c(H2O2) > pH = 7. Ten aromatic intermediates were formed during the degradation of LFXN, which were further degraded to F−, NH4+, NO3−, CO2 and H2O. This study provides a promising approach for efficiently treating LFXN antibiotic wastewater by pulsed electrochemical oxidation with a BDD electrode without adding H2O2.

Assessing the electrochemical degradation of reactive orange 84 with Ti/IrO2–SnO2–Sb2O5 anode using electrochemical oxidation, electro-Fenton, and photoelectro-Fenton under UVA irradiation

Today, water shortage problems around the world have forced the search for new treatment alternatives, in this context, electrochemical oxidation technology is a hopeful process for wastewater treatment, although it is still needed exploration of new efficient and economically viable electrode materials. In this way, mixed metal oxide anodes look like promising alternatives but their preparation is still a significant point to study, searching for finding low-cost materials to improve electrocatalytic efficiencies. In an exploration of this kind of highly efficient materials, this work presents the results obtained using an MMO Ti/IrO2–SnO2–Sb2O5 anode. All the prepared anodes exhibited excellent physical and electrochemical properties. The electrochemical oxidation of 100 mL and 200 mg L−1 Reactive Orange 84 (RO 84) diazo dye was studied using 3 cm2 of such synthesized anodes by applying current densities of 25, 50, and 100 mA cm−2. Faster and more efficient electrochemical oxidation occurred at 100 mA cm−2 with 50 mM of Na2SO4 + 10 mM NaCl as supporting electrolyte at pH 3.0. The degradation and mineralization processes of the above solution were enhanced with the electro-Fenton process with 0.05 mM Fe2+ and upgraded using photoelectron-Fenton with UVA light. This process yielded 91% COD decay with a low energy consumption of 0.1137 kWh (g COD)−1 at 60 min. The evolution of a final carboxylic acid like oxalic was followed by HPLC analysis. The Ti/IrO2–SnO2–Sb2O5 is then an efficient and low-cost anode for the photoelectro-Fenton treatment of RO 84 in a chloride and sulfate media.

Preparation of an ultra-long-life porous bilayer Ti/Sb-SnO2 electrode modified by nano-TiC for degradation of phenol

Electrochemical advanced oxidation technology produces hydroxyl radicals and has no secondary pollution, making it one of the most promising technologies for treating organic pollutants in industrial wastewater. Nevertheless, low energy efficiency and short lifetime are the key issues hindering the widespread application of electrodes. In this study, TiC nanoparticles were uniformly dispersed in the deposition solution, and the Ti/Sb-SnO2 electrode was prepared by sol electrodeposition, after calcination, a porous double-layer structure was formed, which improved the catalytic performance and effectively delayed the penetration of industrial wastewater into the electrode. Compared with the Ti/Sb-SnO2 electrode, the electrode life is increased by nearly 6 times, the phenol removal rate reaches 90.64 % (2000 mA/cm2, 1 mol/L H2SO4), the oxygen evolution potential of 2.13 V, a current density of 0.096 A/cm2, a charge transfer resistance of 2.245 Ω. The results show that the porous structure is conducive to providing a larger specific surface area and contact area for the reaction, maximizing the utilization of catalytic active sites, shortens the mass transfer distance between the hydroxyl radicals and pollutants, increases the degradation rate, reduces the corrosion rate of the electrode materials, and improves electrode stability. The unique double-layer structure is obviously different from traditional electrodes, adding a layer of protective barrier, which provides a new idea for prolonging the life of electrodes. The electrode prepared in this study has a simple process, a greatly improved lifespan and an excellent energy utilization rate, which is suitable for industrial application.

Efficient Electrochemical Oxidation of Chloramphenicol by Novel Reduced TiO2 Nanotube Array Anodes: Kinetics, Reaction Parameters, Degradation Pathway and Biotoxicity Forecast.

The key component of electrochemical advanced oxidation technology are high-efficiency anodes, and highly efficient and simple-to-prepare materials have generated a lot of interest. In this study, novel self-supported Ti3+-doped titanium dioxide nanotube arrays (R-TNTs) anodes were successfully prepared by a two-step anodic oxidation and straightforward electrochemical reduction technique. The electrochemical reduction self-doping treatment produced more Ti3+ sites with stronger absorption in the UV-vis region, a band gap reduction from 2.86 to 2.48 ev, and a significant increase in electron transport rate. The electrochemical degradation effect of R-TNTs electrode on chloramphenicol (CAP) simulated wastewater was investigated. At pH = 5, current density of 8 mA cm-2, electrolyte concentration of 0.1 M sodium sulfate (Na2SO4), initial CAP concentration of 10 mg L-1, CAP degradation efficiency exceeded 95% after 40 min. In addition, molecular probe experiments and electron paramagnetic resonance (EPR) tests revealed that the active species were mainly •OH and SO4-, among which •OH played a major role. The CAP degradation intermediates were discovered using high-performance liquid chromatography-mass spectrometry (HPLC-MS), and three possible degradation mechanisms were postulated. In cycling experiments, the R-TNTs anode demonstrated good stability. The R-TNTs prepared in this paper were an anode electrocatalytic material with high catalytic activity and stability, which could provide a new approach for the preparation of electrochemical anode materials for difficult-to-degrade organic compounds.

Removal of contaminants of emerging concern and Escherichia coli from effluent using an optimized electrochemical reactor

Contaminants of emerging concern (CECs) in wastewater are a matter of great importance as they have a huge environmental impact. This work investigated the electrochemical oxidation (EO) technology as an alternative tertiary treatment in wastewater treatment plants (WWTP) aiming to simultaneous remove CECs and Escherichia coli. Platinum titanium (Pt/Ti) and metal mixed oxide (MMO, RuO2–IrO2/Ti) electrode materials with different shapes (bar, mesh and circular mesh) were tested. The results obtained showed that removal rate not only depends on CECs structure and physicochemical characteristics, but electrode material and shape play a key role in the whole treatment process. Overall, the removal efficiency increased (20–50%) for the recalcitrant CECs when using MMO with the electrode characterized by a higher surface area with a circular-mesh as both anode and cathode. Varying the current intensity had a relatively minor effect on the yield of CECs removal. CECs removals were greater than 90% with simultaneous removal of E. coli within 2 h. Overall, EO can be considered an eco-friendly process since no reagents were added and has a low estimated treatment cost of 1.1 €/m3.

Photo‐Alternating Current‐Electro‐Fenton Process for Pollutant Removal and Energy Usage from Industrial Wastewater: Response Surface Approach Optimization of Operational Parameters

AbstractDuring the last two decades, there has been an increase in interest the use of electrochemical and advanced oxidation technologies for treatment of industrial wastewater. Efficacy of several techniques for treating distilling industry wastewater (DIW), UV light, H2O2, combination of UV and H2O2, direct current (DC) and alternating current (AC)‐electro‐Fenton (EF), and UV combined with DC/AC+EF (UV+DC/AC+EF) processes were all examined. The findings revealed that compared to the UV, H2O2, UV/H2O2, DC/AC+EF, and UV+DC+EF technologies, the UV+AC+EF process resulted total color of 100 % and COD of 100 % elimination efficiency with low energy use 4 kWhr m−3. A response surface methodology (RSM) approach that relies on central composite design (CCD) was used to optimize the UV+AC+EF technology‘s parameters for treating DIW. Optimal conditions were obtained by utilizing mathematical and statistical methods in order to maximize COD elimination (89.50 %) and minimize energy consumption (2.775 kWhr m−3). The parameters for this experiment were as follows: UV power: 32 W, H2O2: 320 mg L−1, COD: 2400 mg L−1, CD: 0.2 A dm−2, and duration: 111 min. The combined efficiency of removing % COD using the UV, AC+EF, and UV+AC+EF processes was used to determine the synergistic effect, which was 13.65 %. As a consequence of this, treating industrial wastewater with a hybrid UV+AC+EF technique is significantly more successful.

Removal of chemical oxygen demand and ammonia nitrogen from high salinity tungsten smelting wastewater by one-step electrochemical oxidation: From bench-scale test, pilot-scale test, to industrial test

In recent years, electrochemical oxidation (EO) shows the characteristics of green and high efficiency in removing chemical oxygen demand (COD) and ammonia nitrogen (NH3–N) from wastewater, which has been favored by researchers. However, at present, most of current studies on EO remain in laboratory stage, reports about pilot-scale or even industrial tests with large treatment capacity are few, which slowing down the use of the advanced technology to practical application. In this study, bench-scale tests, pilot-scale tests (treatment capacity 200–500 L/h), and industrial tests (treatment capacity 100 m3/h) were carried out by EO technology in view of the characteristics of tungsten smelting wastewater (TSW) with high salinity (NaCl), COD, and NH3–N. Results showed that the removal of COD and NH3–N was a competitive reaction in the EO process, and COD could be removed more preferentially than NH3–N. When NH3–N content was low, the influent pH had a minimal effect on its removal, and when NH3–N content was high, increasing the influent pH was beneficial to its removal. Industrial tests showed that the one-step removal of COD and NH3–N in TSW met the standard, and the power consumption per cubic meter of wastewater was only 4.2 kW h, and the treatment cost was much lower than the two-step process of “breaking point chlorination to remove NH3–N and adding oxidant to remove COD”. This study has successfully realized industrial application of EO technology in TSW treatment for the first time and provided a successful case, which is helpful to accelerate the popularization and application of this technology in the field of high salinity organic ammonia nitrogen wastewater treatment.

MOF-derived ZrO2-C nanoparticles modified PbO2 electrode for high-efficiency electrocatalytic degradation of nitrophenolic compounds in wastewater

Highly performed electrode possessed excellent electrocatalytic performance for electrochemical oxidation technology remains a huge challenge. Here, we prepared a durable metal–organic frameworks (MOF)-derived materials doped PbO2 electrode to improve the electrocatalytic performance and service life. The prepared UiO-66 derived ZrO2-C nanoparticles doped PbO2 composite electrode had more active sites, improved conductivity, higher hydroxyl radical (OH) generation capacity, and excellent stability. The composite PbO2 electrode with ZrO2-C nanoparticles doping amount of 4 g L-1 had the best electrocatalytic activity, and the 2, 4, 6-trinitrophenol (TNP) removal rate was up to 94.48% after 140 min of electrolysis, whereas that of pure PbO2 was only 68.33%. Besides, the degradation conditions were further optimized and the electrochemical oxidation degradation pathway of TNP was proposed. Thus, we can conclude that MOF-derived doped PbO2 anode has greater promising application potential in the electrocatalytic degradation of phenolic compounds in wastewater.

Treatment of high chlorine-containing composting leachate biochemical effluent by Ti/RuO2-IrO2 anodic electrochemical oxidation: Optimization and evolution of pollutants

In this paper, the treatment of composting leachate biochemical effluent (CLBE) by electrochemical oxidation (EO) with Ti/RuO2-IrO2 as the anode could achieve concomitantly organic carbon removal (COD) and nitrogen removal (NH3-N), taking advantage of CLBE inherent high chlorine content. Under the optimal conditions of the current density of 90 mA·cm−2, A/V= 14 m−1, d= 1 cm, pH= 8.34 and Cl- concentration of 6000 mg·L−1, 92.19% of NH3-N and 85.59% of TN could be removed in 40 min, and 100% COD removal could be achieved after 100 min, with energy consumption (EC) of 111.09 kW·h·m−3. And the increase in Cl- concentration could reduce the EC of the EO process. In parallel, constructed simple quantitative accounting models for chlorine-containing and nitrogen-containing species in the EO system and clarified the evolution of them. Cl species eventually exist mainly in the form of free chlorine (by-product AOCL concentration always below 2 mg·L−1), while N species were mainly removed in the form of N2 (≈95.10% of TN). Additionally, the gas chromatography-mass spectrometry (GC-MS) showed that the dominant component of dissolved organic matter (DOM) in CLBE was degraded from the initial unsaturated C21-C30 to the saturated C11-C20. And the Excitation emission matrix (EEM) showed that the EO achieved the non-selective degradation of DOM, the refractory humic acid DOM reached 90.74% removal and the readily biodegradable non-humic DOM removal 92.02%, respectively. These results indicated that the EO technology has broad application potential in the treatment of chlorinated wastewater, and coupling it after biological treatment would be a promising method.

Bioaccumulation of Different Organic Micropollutants in Fishes and its Toxicological and Stress Impacts: A Review

Abstract: In the past three decades biological and chemical pollutants have become a serious environmental issue posing major threat to the society, industries and public sectors. Toxic contaminants are produced in most household, agricultural and industrial activities. In the past few years different advanced electrochemical oxidation technologies and low-carbon technologies are being used widely for preventing environmental pollution and remediation of the micropollutants particularly in waterbodies. In these technologies powerful oxidizing agents like hydroxyl radicals are formed electrochemically which degrade organic micropollutants till their mineralization. Fish serves as an effective bioindicator of aquatic health due to their higher trophic position in aquatic food chain and high sensitivity to pollutants. As fishes are consumed by humans globally as a major source of protein, it is also used to indicate the impact of aquatic pollution on human health. In this review we discuss the impact of micropollutants on the fish physiology and the advanced wastewater management techniques used for rapid removal of these pollutants from aquatic ecosystem. Here we discuss both advantages and disadvantages of different commonly used wastewater management techniques which would be beneficial to determine which technology would best suit one’s specific requirements without causing much harm to the environment, a step towards green and sustainable future.

Prospective Life Cycle Assessment for the Electrochemical Oxidation Wastewater Treatment Process: From Laboratory to Industrial Scale.

Electrochemical oxidation (EO) is a promising technology for water purification, but indirect environmental burdens may arise in association with consumption of materials and energy during electrode preparation and process operation. This study evaluated the life cycle environmental impacts of emerging EO technology from laboratory scale to industrial scale using prospective life cycle assessment (LCA) on a quantitative basis. Environmental impacts of EO technology were assessed at laboratory scale by comparing three representative anode materials (SnO2, PbO2, and boron-doped diamond) and other two typical processes (adsorption and Fenton method), which verified the competitiveness of the EO process and identified the key factors to environmental hotspots. Thereafter, LCA of scale-up EO was performed to offer guidance for practical application, and the life cycle inventory was compiled upon thermodynamic and kinetic simulations, empirical calculation rules, and similar technical information. Results demonstrated EO to be effective for destructing recalcitrant organic pollutants, but visible direct benefits might be outweighed by increased indirect environmental burdens associated with the preparation of anode materials, use of electrolytes, and energy consumption during the operation stage at both laboratory scale and larger scale. This necessitated attention to overall life cycle profiles by taking into account reactor design, anode materials, electrolyte and flow pattern, and decentralized location with a large share of renewable power station and rigorous contamination control strategies for wastewater treatment plants.

Energy-efficient electrochemical degradation of ciprofloxacin by a Ti-foam/PbO2-GN composite electrode: Electrode characteristics, parameter optimization, and reaction mechanism

Reducing energy comsuption is crucial to commercialize electrochemical oxidation technologies. In this study, a novel PbO2 composite electrode (Ti-foam/PbO2-GN) was successfully fabricated based on a porous titanium (Ti) foam substrate and a β-PbO2 active layer embedded with multiple graphene (GN) interlayers, and applied as an anode for energy-efficient pulse electrochemical oxidation of ciprofloxacin (CIP). In contrast to PbO2 and Ti-foam/PbO2 electrodes, the Ti-foam/PbO2-GN electrode surface exhibited a more compact structure, smaller crystal grain size, and greater electrochemical active surface area. CIP removal of 89.7% was obtained with a low energy consumption (EE/O) of 6.17 kWh m−3 under pulse electrolysis conditions with a current density of 25.00 mA cm−2, pulse frequency of 5000 Hz, and pulse duty cycle of 50.0%. Up to 70.7% of the energy was saved in the pulse current mode compared to the direct current mode. Narrowing the electrode spacing to 2 cm facilitated the mass transfer process and enhanced oxidation efficiency. According to the intermediates identified, the pulse electrolysis of CIP primarily involved hydroxylation of the quinolone ring, breaking of the piperazine ring, defluorination, and decarboxylation processes, and a possible degradation mechanism of CIP was proposed. The continuous oxidation performance of CIP and the relatively low leaching of Pb2+ suggested that the Ti-foam/PbO2-GN electrode exhibited excellent stability, repeatability, and safety. The degradation results of CIP in real water also exhibits the great potential of environmental application. As a result, pulse electrochemical oxidation using a Ti-foam/PbO2-GN electrode has proven to be an energy-efficient and promising alternative for antibiotic wastewater treatment.

Generation, toxicity, and reduction of chlorinated byproducts: Overcome bottlenecks of electrochemical advanced oxidation technology to treat high chloride wastewater

Electrochemical advanced oxidation process (EAOP) is recommended for high-strength refractory organics wastewater treatment, but the accompanying chlorinated byproduct generation becomes a bottleneck that limits the application of this technology to actual wastewater. In this study, we applied EAOP (0.4-40 mA cm−2) to treat ultrafiltration effluent of an actual landfill leachate, and quantitatively assessed the toxicities of the dominant chlorinated byproducts in EAOP-treated effluent. Considering both toxic effect and dose, it followed the order: active chlorine > chlorate > perchlorate > organochlorines. The toxic active chlorine could spontaneously decompose by settling. And secondary bioreactor originally serving for denitrification could be used to reduce perchlorate and chlorate. The effects of residual active chlorine and extra carbon addition on simultaneous denitrification, perchlorate, and chlorate reduction were investigated. It seemed that 20 mg of active chlorine was an acceptable level to bioactivity, and sufficient electron donors favored the removal of chlorate and perchlorate. Pseudomonas was identified as an active chlorine tolerant chlorate-reducing bacteria. And Thauera was responsible for perchlorate reduction under the conditions of sufficient carbon source supply. Our results confirmed that the perchlorate and chlorate concentrations in the effluent below their health advisory levels were achievable, solving the issue of toxic chlorinated byproduct generation during EAOP. This study provided a solution to realistic application of EAOP to treat high chloride wastewater.

Reactive species conversion into 1O2 promotes substantial inhibition of chlorinated byproduct formation during electrooxidation of phenols in Cl−-laden wastewater

The generation of chlorinated byproducts during the electrochemical oxidation (EO) of Cl−-laden wastewater is a significant concern. We aim to propose a concept of converting reactive species (e.g., reactive chlorines and HO• resulting from electrolysis) into 1O2 via the addition of H2O2, which substantially alleviates chlorinated organic formation. When phenol was used as a model organic compound, the results showed that the H2O2-involving EO system outperformed the H2O2-absent system in terms of higher rate constants (5.95 × 10−2 min−1vs. 2.97 × 10−2 min−1) and a much lower accumulation of total organic chlorinated products (1.42 mg L−1vs. 8.18 mg L−1) during a 60 min operation. The rate constants of disappearance of a variety of phenolic compounds were positively correlated with the Hammett constants (σ), suggesting that the reactive species preferred oxidizing phenols with electron-rich groups. After the identification of 1O2 that was abundant in the bulk solution with the use of electron paramagnetic resonance and computational kinetic simulation, the routes of 1O2 generation were revealed. Despite the consensus as to the contribution of reaction between H2O2 and ClO− to 1O2 formation, we conclude that the predominant pathway is through H2O2 reaction with electrogenerated HO• or chlorine radicals (Cl• and Cl2•−) to produce O2•−, followed by self-combination. Density functional theory calculations theoretically showed the difficulty in forming chlorinated byproducts for the 1O2-initiated phenol oxidation in the presence of Cl−, which, by contrast, easily occurred for the Cl•-or HO•-initiated phenol reaction. The experiments run with real coking wastewater containing high-concentration phenols further demonstrated the superiority of the H2O2-involving EO system. The findings imply that this unique method for treating Cl−-laden organic wastewater is expected to be widely adopted for generalizing EO technology for environmental applications.

A review of electrochemical oxidation technology for advanced treatment of medical wastewater.

Antibiotics widely exist in medical wastewater, which seriously endanger human health. With the spread of the COVID-19 and monkeypox around the world, a large number of antibiotics have been abused and discharged. How to realize the green and efficient treatment of medical wastewater has become a hot research topic. As a common electrochemical water treatment technology, electrochemical oxidation technology (EOT) could effectively achieve advanced treatment of medical wastewater. Since entering the 21st century, electrochemical oxidation water treatment technology has received more and more attention due to its green, efficient, and easy-to-operate advantages. In this study, the research progress of EOT for the treatment of medical wastewater was reviewed, including the exploration of reaction mechanism, the preparation of functional electrode materials, combining multiple technologies, and the design of high-efficiency reactors. The conclusion and outlook of EOT for medical wastewater treatment were proposed. It is expected that the review could provide prospects and guidance for EOT to treat medical wastewater.

Electrochemical treatment for leachate membrane retentate: Performance comparison of electrochemical oxidation and electro-coagulation technology.

With the widespread use of membrane in advanced treatment of leachate, China produces a large amount of leachate membrane retentate (LMR) (≈23.4 million tons) annually, which is usually treated by incineration or recirculation in engineering, but these technologies have many drawbacks. LMR is suitable for electrochemical treatment due to its high electrical conductivity. This study compared the performances of electrochemical oxidation (EO) and electro-coagulation (EC) technology on LMR treatment under different experimental conditions, including anode material, current density, initial pH and reaction time. We found that EO optimal conditions achieved 70.1%, 83.1%, 78.7%, 98.7%, and 69.7% removal of total organic carbon (TOC), UV absorption (at 254nm), chromaticity, ammonia nitrogen (NH3-N), and total nitrogen (TN), respectively. Compared with EO, EC exhibited a similar removal ability for orgainics and better removals of chroma, but much less performance for removing nitrogen pollutants in the same reaction time, that is, removals of NH3-N and TN were only 31.5% and 36.2%, respectively. Meanwhile, EC showed much higher instantaneous current efficiency of COD than EO under its optimal reaction time (120min). In addition, the UV-Vis spectra and 3D fluorescence spectra indicated that EO exhibited relatively outstanding performance in decomposing dissolved organic matter (DOM) with rather complicated structures than EC. Also, the flow field-flow fractionation technique demonstrated that EO preferentially destroy humic-like, large molecular weight DOM, and converting them to smaller molecules, which resulted in more volatile organic compounds in EO samples than EC samples. While EC had little selectivity in the removal of organics, except humic-like DOM with relative small molecular. These findings can provide a theoretical basis for the electrochemical treatment of LMR.

Environmental Life Cycle Assessment (LCA) of Treating PFASs with Ion Exchange and Electrochemical Oxidation Technology

Environmental Life Cycle Assessment (LCA) of Treating PFASs with Ion Exchange and Electrochemical Oxidation Technology

Electrocatalytic degradation of methyl orange and 4-nitrophenol on a Ti/TiO2-NTA/La-PbO2 electrode: electrode characterization and operating parameters.

The anode material plays a crucial role in the process of electrochemical oxidation. Herein, a TiO2 nanotube arrays (TiO2-NTA) intermediate layer and La-PbO2 catalytic layer were synthesized on a Ti surface by the electrochemical anodic oxidation and electrochemical deposition technology, respectively. The prepared Ti/TiO2-NTA/La-PbO2 electrode was used as an electrocatalytic oxidation anode for pollutant degradation. Scanning electron microscopy (SEM) analysis showed that the TiO2-NTA layer possessed a highly ordered and well-aligned nanotube array morphology, and the La-PbO2 layer with angular cone cluster was uniform and tightly bonded. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis indicated that the intermediate layer primarily consisted of the anatase crystal structure of TiO2 and the catalyst layer was made of La-PbO2. Electrochemical analysis revealed that Ti/TiO2-NTA/La-PbO2 electrode exhibited higher oxidation peak current, electrochemical active surface area, and oxygen evolution potential (OEP, 1.64V). Using methyl orange and 4-nitrophenol as model pollutants, electrocatalytic properties of the prepared Ti/TiO2-NTA/La-PbO2 electrode were systematically investigated under different conditions, and the electrochemical degradation fitted well with the pseudo-first-order kinetics model. Efficient anodic oxidation of model pollutants was mainly attributed to the indirect oxidation mediated by hydroxyl radicals (•OH). The total organic carbon (TOC) removal efficiency of methyl orange and 4-nitrophenol was 70.2 and 72.8%, and low energy consumption (2.50 and 1.89 kWh g-1) was achieved after 240min of electrolysis under the conditions of initial concentration of model pollutant, electrode spacing, and electrolyte concentration were 50mg L-1, 2cm, and 0.1mol L-1, respectively. This work provided a new strategy to develop the high-efficiency electrode for refractory pollutants degradation.

Glucose driven self-sustained electro-Fenton platform for remediation of 2,4-dichlorophenoxy herbicide contaminated water

ABSTRACT As electrochemical oxidation technologies are energy-intensive, they are sparsely included in wastewater treatment plants. This study demonstrates a self-reliable glucose driven-electro-Fenton (GD-EF) system for decontamination of 2,4-dichlorophenoxy (2,4-D) herbicides without the supply of external current or voltage. It incorporates a cathode (graphite) which accepts electrons from abiotic glucose oxidation at anode (Pt/Ti or BDD or PbO2/Cu/Ti) and generates in situ H2O2. For the first time, the ability of Pt/Ti, BDD, and PbO2/Cu/Ti anodes in GD-EF and their influence on 2,4-D decontamination rate have been studied. Pt/Ti and PbO2/Cu/Ti exhibited maximum power densities of 60.42 and 219.3 µW cm−2, respectively than BDD (2.418 µW cm−2). Even though Pt/Ti fuel cell exhibited lower power density than the PbO2/Cu/Ti – fuel cell, it had a faster 2,4-D degradation rate of k = 18 × 10−3 s−1. The generated cathodic potential of −0.275 mV vs. Ag/AgCl in the Pt/Ti-fuel cell was sufficient to produce 23 mg L−1h−1 of H2O2. The high performance liquid chromatography analysis reveals the complete transformation of 2,4-D in 540 min and its degradation by 95% in 1080 min. This finding paves the way for greener decontamination of bio-recalcitrant herbicides with zero electrochemical energy consumption.

Performance of Ti/RuO2-IrO2 electrodes and comparison with BDD electrodes in the treatment of textile wastewater by electro-oxidation process

Electrochemical oxidation (EO) technology, which may directly reduce refractory contaminants into simple inorganic molecules like H2O and CO2, is an efficient approach for treating high-concentration wastewater. Boron doped diamond (BDD) electrodes has been extensively researched and used to degrade organic contaminants from real textile wastewater. In this study, two-dimensionally stable anodes, Ti/RuO2-IrO2, were produced and compared with BDD electrodes for the treatment of textile wastewater. This study focuses on the optimization of the produced electrode under different pH and current densities. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that the oxide coating on the Ti plate’s surface was effectively produced. The EO process parameters were optimized using central composite design (CCD) under response surface methodology (RSM), with total organic carbon (TOC), chemical oxygen demand (COD), and color removals as responses and pH, current density, and reaction time as control variables. The analysis of variance (ANOVA) revealed good coefficients of determination (R2) values of.0.90, indicating that the second-order regression model matched the experimental data satisfactorily. In optimized conditions, pH 4 was shown to have the maximum effectiveness for both electrodes. The best treatment efficiency was obtained by applying an 800 A/m2 current for 5 h, taking into account the time component in the different current values employed. BDD had a color, TOC, and COD removal of 93%, 75%, and 48%, respectively, whereas Ti/RuO2-IrO2 had a color, TOC, and COD removal of 88%, 62%, and 41%, respectively. In addition, the toxicity of water treated with the BDD electrode was found to be lower, whereas the toxicity of water treated with the Ti/RuO2-IrO2 electrode was found to be higher.