| In recent years,the ecological and health risks caused by refractory toxic organic pollutants have attracted widespread attention.Phenol-containing wastewater is one of the common,highly toxic and refractory wastewaters,which has a wide range of sources.Due to the stability of the chemical structure of phenolic compounds,toxicity and the complexity of wastewater components,it is still a realistic challenge facing the field of environmental engineering to find an efficient and economical treatment of wastewater containing such pollutants.The electrochemical oxidation method has the characteristics of simple equipment,mild reaction conditions,easy automation,and small footprint,which is widely used to treat phenol-containing wastewater.But its current efficiency is not high,and there is a problem of accumulation of intermediate products.At the same time,the concentration of organic matter in the actual wastewater is high and the fluctuation is large,so the electrocatalytic oxidation of the electrode alone to generate active species cannot meet the actual treatment requirements.Therefore,this is also an urgent problem to be solved in the current electrochemical treatment technology.In this paper,a variety of modified activated carbon fiber(ACF)electrode materials including Ag2O/ACF、TiO2/ACF、Ag2O/TiO2/ACF and Ag-TiO2/ACF electrodes were prepared by the "ship-in-bottle" method,and the related electrode materials were systematically discussed as anode or cathode or using both of them.The electrochemical performance of the dual-electrode electrocatalytic system was constituted,and the influence of key factors such as voltage,Ag or TiO2 modification amount and external source addition of H2O2 on the electrochemical performance of the relevant working electrode were discussed,and the working mechanism of related electrodes was discussed combined with scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),cyclic voltammetry(CV)characterization and analysis techniques.The experimental results were as follows:(1)When Ag2O/ACF electrode was used as anode or cathode for electrocatalytic oxidation of phenol,both had certain catalytic activity.And it had a higher phenol removal rate when used as a cathode.Compared with the anode,the optimal voltage was reduced from 8 V to 4 V,which will greatly save energy.However,the accumulation of intermediate products was more serious,and the stability was not as good as when used as an anode.(2)The Ag-TiO2/ACF electrode was used as the anode and cathode for electrocatalytic oxidation of phenol.It was found that the removal rate of phenol is positively correlated with the amount of Ag doping,the overall degradation rate of the cathode was higher than that of the anode,and the intermediate product p-benzoquinone was not detected when used as a cathode.(3)A new system of electrochemical catalytic oxidation of phenol with bimetallic dual electrode was constructed.The results showed that the phenol degradation rate of the bimetallic dual electrode system increased almost linearly,the concentration of the intermediate product was significantly reduced;The optimal electrode system for degradation of phenol was 14 Ag-M28 TiO2/ACF—28 Ag-M28 TiO2/ACF,which had excellent cycle stability.Repeated 6 times,the degradation rate of phenol was maintained above 90%.(4)The electrocatalytic performance of TiO2/ACF and Ag-TiO2/ACF was enhanced by adding H2O2 from an external source.It was found that the minimum excitation voltage for electro-activated Ti-peroxide at 3 V,and with the increase of voltage,the production of hydroxyl radicals(·OH)gradually increases,which can realize the controllable release of ·OH,so as to meet the needs of treating actual wastewater.(5)SEM,XPS characterization and cyclic voltammetry combined with ·OH and H2O2 analysis was used to characterize the electrochemical performance of ACF,TiO2/ACF,Ag2O/ACF,Ag-TiO2/ACF electrodes,which well revealed the working mechanism of the electrode and the mechanism of electrocatalytic oxidation of phenol. |
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