Role of methoxy and C_(α)-based substituents in electrochemical oxidation mechanisms and bond cleavage selectivity of β-O-4 lignin model compounds

In order to better understand the specific substituent effects on the electrochemical oxidation process of β-O-4 bond, a series of methoxyphenyl type β-O-4 dimer model compounds with different localized methoxyl groups, including 2-(2-methoxyphenoxy)-1-phenylethanone, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanol, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanone, 2-(2,6-dimethoxyphenoxy)-1-(4-methoxyphenyl)ethanol have been selected and their electrochemical properties have been studied experimentally by cyclic voltammetry, and FT-IR spectroelectrochemistry. Combining with electrolysis products distribution analysis and density functional theory calculations, oxidation mechanisms of all six model dimers have been explored. In particular, a total effect from substituents of both para-methoxy(on the aryl ring closing to Cα) and Cα-OH on the oxidation mechanisms has been clearly observed, showing a significant selectivity on the Cα-Cβbond cleavage induced by electrochemical oxidations.

In-situ oriented oxygen-defect-rich Mn-N-O via nitridation and electrochemical oxidation based on industrial-scale Mn_(2)O_(3) to achieve high-performance aqueous zinc ion battery

As a general problem in the field of batteries,materials produced on a large industrial scale usually possess unsatisfactory electrochemical performances.Among them,manganese-based aqueous rechargeable zinc-ion batteries(ARZBs)have been emerging as promising large-scale energy storage systems owing to their high energy densities,low manufacturing cost and intrinsic high safety.However,the direct application of industrial-scale Mn2O3(MO)cathode exhibits poor electrochemical performance especially at high current rates.Herein,a highly reversible Mn-based cathode is developed from the industrial-scale MO by nitridation and following electrochemical oxidation,which triples the ion diffusion rate and greatly promotes the charge transfer.Notably,the cathode delivers a capacity of 161 m Ah g^(-1) at a high current density of 10 A g^(-1),nearly-three times the capacity of pristine MO(60 m Ah g^(-1)).Impressive specific capacity(243.4 m Ah g^(-1))is obtained without Mn^(2+) additive added in the electrolyte,much superior to the pristine MO(124.5 m Ah g^(-1)),suggesting its enhanced reaction kinetics and structural stability.In addition,it possesses an outstanding energy output of 368.4 Wh kg^(-1) at 387.8 W kg^(-1),which exceeds many of reported cathodes in ARZBs,providing new opportunities for the large-scale application of highperformance and low-cost ARZBs.

Colour and organic removal of biologically treated coffee curing wastewater by electrochemical oxidation method

The treatment of biologically treated wastewater of coffee-curing industry by the electrochemical oxidation using steel anode was investigated. Bench-scale experiments were conducted for activated sludge process on raw wastewater and the treated effluents were further treated by electrochemical oxidation method for its colour and organic content removal. The efficiency of the process was determined in terms of removal percentage of COD, BOD and colour during the course of reaction. Several operating parameters like time, pH and current density were examined to ascertain their effects on the treatment efficiency. Steel anode was found to be effective for the COD and colour removal with anode efficiency of 0.118 kgCOD\5h -1\5A -1\5m -2 and energy consumption 20.61 kWh\5kg -1 of COD at pH 9. The decrease in pH from 9 to 3 found to increase the anode efficiency from 0.118 kgCOD\5h -1\5A -1\5m -2 to 0.144 kWh\5kg -1 of COD while decrease the energy consumption from 20.61 kWh\5kg -1 of COD to 12.86 kWh\5kg -1 of COD. The pH of 5 was considered an ideal from the present treatment process as it avoids the addition of chemicals for neutralization of treated effluents and also economical with respect to energy consumption. An empirical relation developed for relationship between applied current density and COD removal efficiency showed strong predictive capability with coefficient of determination of 96.5%.

Indirect Electrochemical Oxidation of 4-Amino-dimethyl-aniline Hydrochloride

The indirect dectrechemical oxidation of 4-amino-dimethyl-aniline hydrochloride containing wastewater generated from vanillin production is presented. Experiments were conducted at a constant current density of 30 rnA/cm^2 via a Ti/Bu-Ti-Sn ternary oxide coated anode and an undivided reactor. During the various stages of the electrolysis, parameters such as the values of chemical oxygen demand（COD） and total organic carbon（TOC） were determined in order to evaluate the feasibility of the electrochemical treatment. The energy consumption and the current efficiency during the electrolysis were calculated. The present study proves the effectiveness of the electrochemical treatment for wastewater resulted from vanillin production.

Study on superoxide and hydroxyl radicals generated in indirect electrochemical oxidation by chemiluminescence and UV-Visible spectra

The generation and transformation of radicals on the cathode of indirect electrochemical oxidation were studied by chemilumines- cence(CL)and UV-Visible spectra in the reactor with a salt bridge that connected the separated chambers.The CL intensity of 4×10^(-9)mol/L luminol on the cathode with bubbling oxygen was about seven times that of the intensity without it,which was because of the generation of reactive oxygen species(ROS).The existence of ROS,especially the generation of the superoxide radical,coul...

Mechanism study of electrochemical oxidation in the terylene diaphragm cell

By using a self-made carbon/polytetrafluoroethylene （C/PTFE） O2-fed as cathode and Ti/IrO2/RuO2 as anode, the effects of electrochemical oxidation of phenol and the coal-gas wastewater containing phenol were studied. The terylene diaphragm which kept pH〉12 in cathodic compartment and pH〈1 in the anodic compartment was selected in the experiment in comparison with the other types of diaphragm. Furthermore, hydroxyl radical （HO·） was determined in the cathodic compartment of the diaphragm cell by electron spin resonance spectrum（ESR） and the fluorescence spectra. Compared with pH, the accumulated HzO2 and the COD removal of the no-diaphragm cell, the mechanism of electrochemical oxidation in the terylene diaphragm cell was supposed. The degradation of phenol was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H2O2, HO· produced by oxygen reduction at the cathode. The mineralization of phenol in the diaphragm cell was better than that in the no-diaphragm cell. When the coal-gas wastewater was treated by the electrolysis system with terylene diaphragm, the average removal efficiency of the volatile phenol and COD were 100% and 79.6%, respectively.

Electrochemical Oxidation of L-Cystenine in SDS/BA/H_2O Microemulsion

The electrochemical oxidation of L-cysteine in an SDS/BA/H_2O microemulsion system was studied with the methods of ultramicroelectrode cyclic voltammetry and AC impedance. The catalytic efficiency of the microemulsion on the electrochemical oxidation increases with the increase of BA or SDS content, but decreases with the increase of the water content because of the effects of BA, SDS and water on the solubilization of L-cysteine in the microemulsion. Furthermore, the catalytic efficiency of the bicontinuous structure is greater than that of an O/W microemulsion system. The results derived from both the rate constant k0 and Gibbs free energy ΔG≠ accord with those from the catalytic efficiency.

Electrochemical oxidation of ammonia-containing wastewater using Ti/RuO_2-Pt electrode

The electrochemical oxidation degradation processes for artificial and actual wastewater containing ammonia were carried out with a Ti/RuO2-Pt anode and a Ti plate cathode. We studied the effects of different current densities, space sizes between the two electrodes, and amounts of added NaCl on ammonia-containing wastewater treatm.ent. It was shown that, after a 30-min treatment under the optimal conditions, which were a current density of 20 mA/cm2, a space size between the two electrodes of I cm, and an added amount of 0.5 g/L of NaC1, the COD concentration in municipal wastewater was 40 mg/L, a removal rate of 90%; and the NH3-N concentration was 7 mg/L, a removal rate of 88.3%. The effluent of municipal wastewater qualified for Class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant （GB 18918-2002）.

Surface State of Carbon Fibers Modified by Electrochemical Oxidation

Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5% which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

Enhanced electrochemical oxidation of phenol by introducing ferric ions and UV radiation

The mineralization of phenol in aerated electrochemical oxidation has been investigated.The results show that a cathodic Fenton process can occur when the Ti-0.3Mo-0.8Ni alloy material is used as cathode in solution containing ferric or ferrous ions; moreover,the reinforcement of cathodic Fenton process on the total organic carbon (TOC) removal rate of phenol is quite distinct.Among the metallic ions investigated,the ferric ion is the best catalyst for the electrochemical mineralization of phenol at initial...

Kinetic Studies of Electrochemical Oxidation of 1,3-Benzenedithiol

The electrochemical oxidation of 1, 3-benzenedithiol was investigated in a 0. 100 mol/L tetrabutylammonium perchlorate/acetonitrile electrolyte. The electrochemical techniques used were potential sweep, bulk electrolysis, rotating disc and the potential step method. The combination of the techniques yielded the number of electrons transferred per molecule, the reaction order, the transfer coefficient, the diffusion coefficient and concentration of dithiol anions, the standard heterogeneous rate constant as well as the formal potential and equilibrium constant of the preceeding dissociation reaction. This paper also illustrates the methods for studying the electrode kinetics of reactions which (a) involve a chemical reaction preceeding the electron-transfer process, (b) have insoluble polymer products, and (c) are totally irreversible.

Electrochemical Oxidation of Chlorimuron-ethyl on Ti/SnO_2-Sb_2O_5/PbO_2 Anode for Waste Water Treatment

The electrochemical oxidation of chlorimuron-ethyl on metry. The electrochemical behaviour of the electrode in a sodium Ti/SnO2-Sb2O5/PbO2 electrode was studied by cyclic voltamsulfate solution and in the mixture solution of sodium sulfate and chlorimuron-ethyl was studied. The experimental results of cyclic voltammetry show that the acidic medium was suitable for the efficient electrochemical oxidation of chlorimuron-ethyl. Some electro-generated reagent was formed in the electrolysis process and chlorimuron-ethyl could be oxidized by the electro-generated reagent. A Ti/SnO2-Sb2O5/PbO2 electrode was used as the anode and the electrolysis experiment was carried out under the optimized conditions. The electrolysis process was monitored by UV-Vis spectrometry and high performance liquid chromatography（HPLC）, and the chemical oxygen demand（COD） was determined by the potassium dichromate method. The mechanism of chlorimuron-ethyl to be oxided was studied primarily by the cyclic voltammetry and UV-Vis spectrometry. The results of electrolysis experiment demonstrate the possibility of the electrode to be used as an anode for the electrochemical treatment of chlorimuron-ethyl contained in waste water.

Effects of electrochemical oxidation on surface and mechanical properties of dry-jet wet spun carbon fibers

The surface of dry-jet wet spun carbon fibers(CFs)is relatively smooth compared with those of wet spun CFs,which results in weak interfacial interactions between the fiber and the polymer resin.A surface functionalization treatment is particularly important to unleash the full potential of the superior mechanical properties of dry-jet wet spun CFs.In this study,the effects of electrochemical oxidation treatment time and current density on the surface structures and the mechanical properties of dry-jet wet spun CFs were investigated.The interlaminar shear strength of the CFs improves significantly from 69 to 84 MPa after 120 s of treatment.Further structural analysis reveals that the improvements are due to the addition of oxygen-containing functional groups and the optimization of the morphology on the surface of the CFs.

The Characteristic of Electrochemical Oxidation of Aniline on SnO_2/Ti Electrode

The characteristic of electrochemical oxidation of aniline on SnO 2/Ti electrode is studied. The results indicate that SnO 2/Ti electrode doped F plays a wonderful role in the oxidation of aniline comparing with Pt electrode. The kinetics factors that influence the oxidation rate of aniline on the SnO 2/Ti electrode are determined by the dissolving of the film on the electrode. The dissolving of the film consisted of intermediate products on the electrode is the slow step. The effects of aniline concentration, pH in aniline solution and the current density( i )on the rate of aniline oxidation, the complexity of intermediate products and the basic category of the intermediate products consisted of the film are introduced.

Enhanced electrochemical oxidation of perfluorooctanoic acid on Ti/SnO_(2)-Sb electrode by surface morphology regulation

Electrochemical oxidation is an effective method to degrade persistent organic pollutants.However,due to the limited catalytic activity of traditional thin film electrodes,the anodic oxidation process is slow and usually requires high energy consumption.Herein,Ti/SnO_(2)-Sb electrode with regulated surface structure was reported to enhance the performance for electrochemical oxidation of persistent organic pollutants.The electrode deposited with SnO_(2)-Sb nanoneedles(Ti/N-SnO_(2)-Sb)showed higher oxidation activity.Its kinetic constant for perfluorooctanoic acid(PFOA)oxidation was 2.0 h^(-1)and the total organic carbon removal rate was 81.7%(4 h)at a relatively low current density of 6 mA/cm^2.Compared with Ti/SnO_(2)-Sb thin film and nanoparticles,Ti/N-SnO_(2)-Sb significantly improved the electrochemical active area and·OH yield,and simultaneously reduced the electron transfer resistance,which enabled it to oxidize PFOA more rapidly even at a lower potential.This work provides a new strategy for promoting the electrochemical oxidation performance.

Degradation and detoxification mechanisms of organophosphorus flame retardant tris(1,3-dichloro-2-propyl)phosphate(TDCPP)during electrochemical oxidation process

Electrochemical oxidation of aqueous tris(1,3-dichloro-2-propyl)phosphate(TDCPP)by using Ti/SnO_(2)-Sb/La-PbO_(2)as anode was investigated for the first time,and the degradation mechanisms and toxicity changes of the degradation intermediates were further determined.Results suggested that electrochemical degradation of TDCPP followed pseudo-first-order kinetics,and the reaction rate constant(k)was 0.0332 min^(−1)at the applied current density of 10 mA/cm^(2)and Na_(2)SO_(4)concentration of 10 mmol/L.There was better TDCPP degradation performance at higher current density.Free hydroxy radical(•OH)was proved to play dominant role in TDCPP oxidation via quenching experiment,with a relative contribution rate of 60.1%.A total of five intermediates(M1,C_(6)H_(11)Cl_(4)O_(4)P;M2,C_(3)H_(7)Cl_(2)O_(4)P;M3,C_(9)H_(16)Cl_(5)O_(5)P;M4,C_(9)H_(14)Cl_(5)O_(6)P;M5,C_(6)H_(10)Cl_(3)O_(6)P)were identified,and the intermediates were further degraded prolonging with the reaction time.Flow cytometer results suggested that the toxicity of TDCPP and degradation intermediates significantly reduced,and the detoxification efficiency was achieved at 78.1%at 180 min.ECOSAR predictive model was used to assess the relative toxicity of TDCPP and the degradation intermediates.The EC_(50)to green algae was 3.59 mg/L for TDCPP,and the values raised to 84,574,54.6,391,and 8920 mg/L for M1,M2,M3,M4,and M5,respectively,indicating that the degradation intermediates are less toxic or not toxic.Electrochemical advanced oxidation process is a valid technology to degrade TDCPP and pose a good detoxification effect.

Tuning the reactivity of TiO_(2)layer with uniform distribution of Sub-5 nm Fe_(2)O_(3)particles via in situ voltage-assisted oxidation for robust catalytic reduction

The trade-off between efficiency and stability has limited the application of TiO_(2)as a catalyst due to its poor surface reactivity.Here,we present a modification of a TiO_(2)layer with highly stable Sub-5 nm Fe_(2)O_(3)nanoparticles(NP)by modulating its structure-surface reactivity relationship to attain efficiency-stability balance via a voltage-assisted oxidation approach.In situ simultaneous oxidation of the Ti substrate and Fe precursor using high-energy plasma driven by high voltage resulted in uniform distribution of Fe_(2)O_(3)NP embedded within porous TiO_(2)layer.Comprehensive surface characterizations with density functional theory demonstrated an improved electronic transition in TiO_(2)due to the presence of surface defects from reactive oxygen species and possible charge transfer from Ti to Fe;it also unexpectedly increased the active site in the TiO_(2)layer due to uncoordinated electrons in Sub-5 nm Fe_(2)O_(3)NP/TiO_(2)catalyst,thereby enhancing the adsorption of chemical functional groups on the catalyst.This unique embedded structure exhibited remarkable improvement in reducing 4-nitrophenol to 4-aminophenol,achieving approximately 99%efficiency in 20 min without stability decay after 20 consecutive cycles,outperforming previously reported TiO_(2)-based catalysts.This finding proposes a modified-electrochemical strategy enabling facile construction of TiO_(2)with nanoscale oxides extandable to other metal oxide systems.

Electrochemical oxidation of recalcitrant organic compounds in biologically treated municipal solid waste leachate in a flow reactor

Biologically-treated municipal solid waste （MSW） leachate still contains many kinds of bit-recalcitrant organic matter. A new plate and frame electrochemical reactor was designed to treat these materials under flow conditions. In the electrochemical oxidation process, NH3 and color could be easily removed by means of electro-generated chlorinefaypochlorite within 20 min. The effects of major process parameters on the removal of organic pollutants were investigated systematically. Under experimental conditions, the optimum operation parameters were current density of 65 mA/cm^2, flow velocity of 2.6 cm/sec in electrode gap, and initial chloride ion concentration of 5000 mg/L. The COD in the leachate could be reduced below 100 mg/L after 1 hr of treatment. The kinetics and mechanism of COD removal were investigated by simultaneously monitoring the COD change and chlorine/hypochlorite production. The kinetics of COD removal exhibited a two-stage kinetic model, and the decrease of electro-generated chlorine/hypochlorite production was the major mechanism for the slowing down of the COD removal rate in the second stage. The narrowing of the electrode gap is beneficial for COD removal and energy consumption.

Electrochemical oxidation of 1H,1H,2H,2H-perfluorooctane sulfonic acid(6:2 FTS) on DSA electrode:Operating parameters and mechanism

The 6：2 FTS was the substitute for perfluorooctane sulfonate（PFOS） in the chrome plating industry in Japan. Electrochemical oxidation of 6：2 FTS was investigated in this study. The degradabilities of PFOS and 6：2 FTS were tested on the Ti/SnO2–Sb2O5–Bi2O3anode. The effects of current density,potential,and supporting electrolyte on the degradation of 6：2 FTS were evaluated. Experimental results showed that 6：2 FTS was more easily degraded than PFOS on the Ti/SnO2–Sb2O5–Bi2O3anode. At a low current density of 1.42 mA/cm2,6：2 FTS was not degraded on Ti/SnO2–Sb2O5–Bi2O3,while the degradation ratio increased when the current density ranged from 4.25 to 6.80 mA/cm2. The degradation of 6：2 FTS at current density of 6.80 mA/cm2 followed pseudo first-order kinetics with the rate constant of 0.074 hr-1. The anodic potential played an important role in the degradation of 6：2 FTS,and the pseudo first-order rate constants increased with the potential. The surface of Ti/SnO2–Sb2O5–Bi2O3was contaminated after electrolysis at constant potential of 3 V,while the fouling phenomenon was not observed at 5 V. The fouled anode could be regenerated by incinerating at 600°C. The intermediates detected by ultra-performance liquid chromatography coupled with a triple-stage quadrupole mass spectrometer（UPLC–MS/MS） were shorter chain perfluorocarboxylic acids. The 6：2 FTS was first attacked by hydroxyl radical,and then formed perfluorinated carboxylates,which decarboxylated and removed CF2 units to yield shorter-chain perfluorocarboxylic acids.

LiCoO2-catalyzed electrochemical oxidation of Li2CO3

Lithium carbonate （Li2CO3） is very common in various types of lithium （Li） batteries. As an insulating by-product of the oxygen reduction reaction on the cathode of a Li-air battery, it cannot be decomposed below 4.75 V （vs. Li＋/Li） during recharge and leads to a large polarization, low coulombic efficiency, and low energy conversion efficiency of the battery. On the other hand, more than 10% of the Li ions from the cathode material are consumed during chemical formation of a Li-ion battery, resulting in low coulombic efficiency and/or energy density. Consequently, lithium compensation becomes essential to realize Li-ion batteries with a higher energy density and longer cycle life. Therefore, reducing the oxidation potential of Li2CO3 is significantly important. To address these issues, we show that the addition of nanoscaled LiCoO2 can effectively lower this potential to 4.25 V. On the basis of physical characterization and electrochemical evaluation, we propose the oxidization mechanism of Li2CO3. These findings will help to decrease the polarization of Li-air batteries and provide an effective strategy for efficient Li compensation for Li-ion batteries, which can significantly improve their energy density and increase their energy conversion efficiency and cycle life.