| The electrochemical oxidation water treatment technology has attracted much attention because of its remarkable effect on the treatment of organic pollutants which are difficult to biodegrade and hazardous chemical composition,and its high efficiency,easy operation and green safety.However,the commonly used electrode materials have shortcomings such as short life,poor stability,complex fabrication process and high price.Furthermore,these traditional electrode materials are generally two-dimensional planar materials with small specific surface area.Water flow can only pass through the electrode surface in parallel,so the efficiency of the reactor is relatively low.How to increase the effective area of the electrode and improve the efficiency of the reactor is a key problem to be solved in the development of electrochemical oxidation technology.In order to overcome the shortcomings of planar or massive two-dimensional electrodes,three-dimensional electrode materials have been developed gradually in recent years,which makes electrochemical filtration technology develop,enhances the mass transfer effect,significantly improves the efficiency of adsorption and oxidation,has the advantages of synergistic effect and kinetics,and is very suitable for the treatment of such refractory organic pollutants.Therefore,the degradation of aniline was studied in a self-designed high-throughput CNT electrochemical filter reactor,and the factors influencing the degradation efficiency of aniline and the degradation mechanism were explored.The effluent concentration of aniline and current utilization efficiency after degradation by the reactor were the main evaluation indexes,the three-electrode working system was used to study the effects of water qualities?electrolyte concentration,initial pH,initial aniline concentration?and operating conditions?anode potential,flow?on the degradation of aniline in the reactor during operation in order of recirculation mode and one-pass mode.The results showed that:The reactor is operated in recirculation mode,the electrolyte concentrations of anhydrous sodium sulfate are 0.001 mol/L,0.01 mol/L and 0.1 mol/L,the concentration of aniline in effluent decreases first and then increases with the increasing of electrolyte concentration.Moreover,the electrolyte concentration is too high,and the current utilization efficiency of the aniline in the reactor is lowered.When the electrolyte concentration is 0.01mol/L,the concentration of t aniline degraded by the reactor is the lowest;the acidity?pH=2.0 and pH=5.0?and Alkaline conditions?pH=10.0?are not conducive to the removal of aniline in the reactor.At pH 7.0,the concentration of aniline in effluent degraded by the reactor is the lowest;the initial concentrations of aniline are20mg/L,30mg/L,40mg/L and 60mg/L,with the increasing of the initial concentration of aniline,the overall removal quality of aniline in the reactor first increased and then decreased.When the initial concentration of aniline was 40mg/L,the overall removal quality of aniline in the reactor was the largest up to 7.87mg,with the removal rate is 82.36%;when the anode potential are 0.5V,1.0V,1.5V and 2.0V,the larger the anode potential is,the lower the effluent aniline concentration degraded by the reactor is,when the anode potential is 2.0V,the effluent aniline concentration is the lowest;the flow are 5mL/min,10mL/min and 15mL/min,with the flow Increases,the concentration of aniline in effluent degraded by reactor first decreased and then increased,the minimum concentration of the effluent of aniline at 10mL/min.The reactor is operated in one-pass mode,the influence of electrolyte concentration,initial pH value,anode potential and initial concentration of aniline on the effluent aniline concentration degraded by the reactor and the optimal parameters are the same as operated in a recirculation mode.When the flow are 5mL/min,10mL/min and 15mL/min,the effluent aniline concentration degraded by the reactor gradually increases with the increase of the flow,the flow is 5mL/min,the effluent aniline concentration after the reactor degradation is the lowest.However,when the flow was 10 mL/min,the overall removal quality of aniline with the reactor is the maximum up to13.21mg,with the removal rate is 22.5%.The reactor operates in recirculation mode and one-pass mode,in the same experimental parameters of water qualities and operating conditions,with the increase of reaction time,the current utilization efficiency of the reactor in the recirculation mode of operation to degrade aniline gradually decreased,but it can remain relatively stable in one-pass mode,the current utilization efficiency of the one-pass mode is generally higher than that of the recirculation mode except that the pH value is acidic?pH=2.0 and pH=5.0?and the anode potential is smaller?1.0V and1.5V?,with the initial concentration of simulated aniline wastewater is 40 mg/L,the anode potential is2.0V,the initial pH value is 7.0,and the flow is 10 mL/min.When the concentration of anhydrous sodium sulfate in electrolyte is 0.001 mol/L,the reaction time is 120 minutes,the current utilization efficiency of one-pass mode is 5.66 times that of recirculation mode.The optimum water quality and operation conditions for aniline degradation were both as follows:initial concentration of simulated aniline wastewater was 40 mg/L,electrolyte anhydrous sodium sulfate concentration was 0.01 mol/L,anode potential was 2.0V,initial pH value was 7.0,and flow was 10 ml/min.Under these conditions,the removal efficiency of aniline can reach82.36%,the current utilization efficiency is 0.0725 mg/C,the removal efficiency of aniline can reach 22.5%and the current utilization efficiency is 0.1677 mg/C.Cyclic Voltammetry?CV?and Normal Pulse Voltammetry?NPV?were used to investigate the electrochemical behavior of aniline on CNT electrode.CV curves showed that the pH value and aniline concentration of the reaction system had a certain effect on the reaction of aniline on CNT electrode.The oxidation peak appeared around 0.5V?vs Ag/AgCl?and the oxygen evolution potential appeared around 1.0V?vs Ag/AgCl?respectively.The lower oxidation potential and higher oxygen evolution potential indicated that CNT electrode had a good performance for the oxidation degradation of aniline.NPV curves show that the electrochemical filtration process has a larger polarization current platform and better diffusion and mass transfer effect than conventional electrochemical oxidation process.The study on the changes of TOC,NO3-and pH value in the reaction system shows that the mineralization degree of aniline is much lower than the removal rate,which indicates that there are a large number of intermediate products in the degradation process of aniline.The nitrate concentration increases with the increase of reaction time,and the pH value decreases with the increase of reaction time.It also provides a basis for the analysis of the intermediate products of aniline,combined with LC-MS analysis showed that there might be some intermediate products such as phenylhydrazine,methylaniline in the degradation process of aniline. |
PDF Full Text Request