Degradation Of Diclofenac In Wastewater By Three-dimensional Electrocatalytic System

Diclofenac is a kind of nonsteroidal anti-inflammatory drug.Its widespread distribution and complex structure in the environment have attracted researchers' attention.Since the three-dimensional electrode electrocatalytic technology can use hydroxyl radicals and other strong oxidants to mineralize this kind of trace refractory pollutants completely,it caused a lot of attention.In this study,the purpose is to improve the electrochemical oxidation performance and stability of the three-dimensional electrocatalytic reactor for diclofenac removal.The specific research contents and results are as follows:The particle electrodes doped with different active metals were prepared by impregnation method.Activated carbon served as the substrate and six kinds of metals served as catalysts.After compared and selected,two kinds of catalysts,Sn and Mn,were prepared and synthesized on activated carbon.The adsorption ability,catalysis ability and stability of AC/Sn-Mn particle electrode were evaluated and characterized.Consequently,among all the particle electrodes,AC/Sn-Mn has the largest specific surface area and the maximum H2O2 production,as well as the highest TOC removal and mineralization current 70%,7.34%,respectively.After that,the preparation conditions of AC/Sn-Mn electrode were optimized.At 0.5 mol/L immersion solution,1:1 Sn/Mn ratio,380 ? calcination temperature,and 5 h calcination time,TOC remocal can reach 73%.The optimized AC/Sn-Mn was analyzed by SEM,EDS,XRD and XPS.The results showed that the adsorption ability and stability of AC/Sn-Mn was excellent.After that,optimized the three-dimensional electrode reactor and its effect on diclofenac pollutant removal.The parameters influencing efficiency of the reactor were studied.The optimum reaction parameters were 6 V applied voltage,3.5 cm electrode spacing,70% particle electrode filling ratio,pH 6,0.25 mol/L NaCl concentration.At this time,the predicted removal rate of TOC was 87%,MCE was 12%,and the actual removal rate was 83.72%.After that,TOC removal,MCE and current distribution of the four electrode types were determined by experiment to choose proper electrode distribution.Meanwhile,COMSOL Multiphysics software was used to simulate the potential distribution of the reator.It was found that the distribution of two anodes and one cathode distribution is relatively uniform and is helpful to suppress the occurrence of side reactions,which will also improve the treatment efficiency of diclofenac and provide theoretical support for the design optimization of the reactor.Finally,optimized continuous flow reactor and studied degradation of diclofenac pollutants.Based on the optimization of the static three-dimensional electrocatalytic reactor,the structure and operating parameters of the continuous flow reactor were optimized.The optimum parameters of the continuous flow reactor are as follows: 3 min hydraulic retention time,70% particle electrode,3 cm electrode distance,7 V applied voltage,0.25 mol/L electrolyte concentration,the TOC removal can reach 74.26%,and MCE can reach 4%.Besides,the degradation pathways of diclofenac in the reaction process were analyzed.Based on the analysis of intermediates by LC-MS,it was deduced that the possible degradation mehods were dehalogenation,hydroxylation and N-H bond cleavage.The restriction steps of further mineralization were obtained as a theoretical support for reactor improving to improve the effectiveness of the reaction system.