Study On The Synergistic Removal Of Heavy Metals And Organic Pollutants In Water By The Enhanced Electroreduction/Electrooxidation Processes

It is difficult for efficient treatment of industrial wastewaters containing heavy metal or refractory organic pollutants.When the wastewaters contained both heavy metal and organic pollutants,it became much more difficult.In addition to the removal of heavy metal itself,it is also necessary to consider the effect of organic matter on the removal of heavy metal.The wastewaters containing heavy metal and refractory organic pollutants are widely found in industrial wastewaters such as electroplating,metallurgy and dyes.In this paper,Cu-SMX wastewater consisting of Cu2+and refractory organic compound Sulfamethoxazole(SMX)was used as the target.Cu2+was removed first by the electroreduction method using the RuO2/Ti cathode.And then SMX was degraded by electro-Fenton(EF)process using an activated carbon fiber(ACF)cathode.On this basis,the degradation process of SMX treated by EF method and the reaction mechanism of on the surface of ACF were also studied.At last,sunlight was introduced to form Solar photoelectro-Fenton(SPEF)process for strengthening mineralization ability to improve the mineralization rate of SMX.The main results are as follows:(1)Simultaneous removal of Cu2+and SMX from mixed wastewater by electrochemical method:The integrated device with RuO2/Ti as the anode and ACF as the cathode cannot remove Cu2+and SMX in the mixed wastewater at the same time.When ACF is uesded as a cathode,whether in deionized water or in SMX solution,the Cu2+removal rate is very low and there is no repeatability.It is impossible to remove Cu2+and realize the degradation of SMX through EF simultaneously.(2)Electrochemical degradation of SMX after removing Cu2+from wastewater:RuO2/Ti electrodes were used as anode and cathode at the same time.The optimal reaction conditions for Cu2+removal were found,that is,under RuO2/Ti anode and RuCh/Ti cathode conditions,when the initial Cu2+concentration was 33?35 mg L-1,the optimal current intensity was 0.12 A,the optimal initial pH was 3.00,and the optimal treatment time was 180 min.Under this optimal conditions,about 95.0%of Cu2+can be removed,while the removal rate of SMX is about 22.3%,and the mineralization is 8.2%.Then the wastewater was treated by EF process,SMX was completely degraded within 120 min,and the TOC removal rate of was 66.1%after 360 min electrolysis.(3)Electrochemical degradation of SMX by EF method:200 mg L-1 SMX was treated under the optimum conditions:initial Fe2+1.00 mM,initial pH 3.00,40 mg L-1 O2,and current intensity=0.36 A.SMX was completely degraded within 90 min,while the SMX degradation followed a pseudo-first-order kinetic with the apparent rate constant 3.54 × 10-2 min-1.The TOC removal rate at 360 min was 64.7%.(4)The reaction mechanisms on the surface of ACF cathode:ACF with larger specific surface area can stably produce higher concentration of H2O2.1800-2000 ?M H2O2 can be electrogenerated from ACF cathode under the condition of 0.36 A and initial pH 3.00.Fenton-like reaction of Cu2+/Cu+occurs on the surface of the ACF and-OH was generated.However,the deposition of copper on the surface of ACF may block the ACF,resulting in the adverse effect of the decrease of*OH production.The clogging of ACF by Cu2+ is irreversible,when the reaction is in process,the clogging affects the degradation of SMX on the ACF cathode surface largely.(5)Efficient mineralization of SMX by SPEF process:Compared with EF,SPEF can mineralize SMX more efficiently,and its mineralization current efficiency is also much higher.The TOC removal is 77.1%at 360 min.The higher the initial concentration of SMX,the higher the TOC removal,but the higher the remaining TOC content.The PEF process consisting of UVA,UVC and EF can replace SPEF to avoid the adverse effects of outdoor weather on the process.This thesis contains 47 Figures,15 Table,and 114 References.