Construction Of Electrochemical Coupling Membrane Filtration System And Research On Removal Of Small Molecular Organic Pollutants

The wide variety of synthetic small molecule organic chemicals（SOCs）has brought huge economic growth and is accompanied by serious water pollution problems.Moreover,the stability and anti-biodegradation of SOCs make it very difficult to treat.Electrochemical membrane filtration process is considered as one of the most promising water or wastewater treatment methods.Therefore,in this paper,a plate-type electrochemical filter with electrified carbon nanotube membrane（ECM）as flow-through anode was designed and constructed for SOCs treatment,and focusing on the limiting phenomenon of natural organic matters（NOMs）for the application of ECM.Meanwhile,the improved methods for the application process of plate-type electrochemical filter in the presence of NOMs were preliminary discussed.The main research results were as follows:The removal efficiency and degradation mechanism of SOCs by the plate-type electrochemical filter were explored.The results showed that under the conditions of10 mmol·L^-1Na₂SO₄electrolyte,electric field 3 V,single flow rate of 1.5 m L·min^-1,rhodamine B,methyl orange,tetracycline hydrochloride and bisphenol A with a concentration of 10 mg·L^-1could be effectively degraded,and their removal efficiencies could exceed 95%,94%,90%and 93%,respectively.Moreover,the degradation performance of ECM did not decrease significantly after continuous use for 36 h,for example,the removal rate of 10 mg·L^-1Rh B was as high as 98%.Experiments such as quenching and EPR showed that the degradation of SOCs in the plate-type electrochemical filter system mainly depended on the direct electro-oxidation of the flow-through ECM anode.The effects of different NOMs components on the oxidative degradation of SOCs in ECM were investigated.The results showed that the deposition of NOMs could alter the electrochemical reactivity of ECM.Bovine serum albumin（BSA）could enhance the electron transfer activity of ECM,but the electro-oxidation of BSA itself also competed with SOCs for the active reaction site of membrane electrode.Therefore,in the presence of BSA,under the influence of its dual effects,the degradation effect of SOCs would first decrease and then increase.Alginate（AA）could inhibit the electron transfer activity of ECM,and its own electron transfer ability was weak,which leaded to a decrease in the degradation effect of SOCs when AA existed in the water sample.In the presence of humic acid（HA）,the electron transfer activity of ECM was slightly improved,and the HA active reaction site competition ability was weak,so it had no effect on the degradation of SOCs in a short time.Meanwhile,through the analysis of apparent degradation kinetics,it was founded that different components of NOMs had different effects on the electro-oxidation kinetics of ECM.The electro-oxidation and electro-adsorption rate constants of ECM were largest in the presence of BSA,followed by AA and HA.However,in the presence of AA,the electrooxidative performance of ECM was significantly lower than its electrosorption performance.According to the influence of different NOMs on the performance of ECM,the improvement methods of application process of plate-type electrochemical filter were initially explored.The results showed that the pre-coagulation and pre-sedimentation process could effectively avoid the deposition of NOMs on the ECM when the plate-type electrochemical filter wass applied to the SOCs-NOMs water sample.Meanwhile,when persulfate was added into the treatment systemof the plate-type electrochemical filter,the deposition of NOMs on the ECM could not be avoided,but it was helpful for the removal of SOCs.