Activated Peroxymonosulfate By A Carbon Cathode With Multi-channels And Its Performance In Degradation Of Organics In Water

Activated persulfate oxidation,as an emerging advanced oxidation technology,is an effective method of mineralizing refractory toxic pollutants.Among the activation methods,the electrochemical activation of persulfate by accepting electrons is easy to operate and environmentally friendly,which is considered to be a promising activation technology.However,in the process of electrochemical activation,the electrostatic repulsion resists the contact between persulfate anions and cathode,leading to low decomposition of persulfate and subsequently low production of radicals,consequently performing slow degradation of pollutants.In this work,a flow-through cathode?FTC?with multi-channels was prepared with the carbonized wood?CW?derived from natural one.By confining peroxymonosulfate?PMS?anions in cathodic microchannels,the collision and contact between PMS and cathode may be enhanced remarkably,which may improve the efficiency of electrochemical activation and enhance the degradation of pollutants.The main research results are listed as follows:?1?The FTC with abundant mesopores,good electrical conductivity,high mechanical strength,a large number of ordered microchannels,and good electrocatalytic activity for PMS was fabricated via one-step carbonization of natural pine.With phenol as the target pollutant,the effects of different reaction conditions?PMS concentration,current density and residence time?on the degradation of phenol by electro-activated PMS in FTC were investigated.Under the conditions of influent phenol concentration of 20 mg/L,influent TOC of 18 mg/L,influent PMS concentration of 6.51 mM,0.05 M Na₂SO₄,current density of 2.75 mA/cm²,influent pH2.87,residence time of 10 min and normal temperature,the PMS decomposition rate reached71.9%by electro-activated PMS in FTC.The removal rates of phenol and TOC were 97.9%and 39.6%,respectively.The EPR experiment results showed that during the process of electrochemical activation of PMS in FTC,a large amount of·OH and SO₄^?-were generated.Meanwhile,the radical quenching experiments also suggested that both·OH and SO₄^?-were involved in the degradation of phenol,and·OH contributed more to the degradation.The results of cycling experiments for five runs proved that the FTC assembled in this study had good stability.?2?By closing the microchannels of CW,a flow-by cathode?FBC?was obtained.Under the same optimized conditions,the decomposition of PMS,the production of free radicals and the performance in the degradation of three phenolic organic compounds?phenol,bisphenol A and 4-chlorophenol?by electro-activated PMS between in FTC and on FBC were compared.The results showed that the decomposition rate of PMS in FTC was 3.78 times that on FBC.Meanwhile,the EPR signal intensities of·OH and SO₄^?-in FTC were also significantly greater than those on FBC.In addition,the removal rates of phenol,bisphenol A and4-chlorophenol by electro-activated PMS in FTC reached 97.9%,90.5%and 87.4%,respectively,while those for FBC were 37.4%,49.0%and 52.1%,respectively.For the removal of TOC,the removal rates of phenol,bisphenol A,and 4-chlorophenol by electro-activated PMS in FTC were 39.6%,48.7%,and 33.3%,respectively,while those for FBC were 15.4%,11.3%and 21.3%,respectively.The above results indicated that FTC had a better electrochemical activation of PMS than FBC,which improved the degradation of organics.Furthermore,it also proved that the microchannels of CW did play a key role in enhancing the electrochemical activation of PMS and the degradation of organics.