掺硼金刚石膜电极降解水中全氟辛酸

Degradation of Perfluorooctanoic Acid in Aqueous Solution on a Boron-Doped Diamond Electrode

采用掺硼金刚石膜电极(Boron-doped diamond,BDD)为阳极的电化学氧化法降解全氟辛酸(Perfluorooctanoic acid,PFOA);对比不同电解质体系中PFOA的脱氟效果,考察初始pH、流速、电流密度、初始浓度和电解质浓度对PFOA脱氟率的影响,估算体系能耗;以甲醇(MeOH)和叔丁醇(TBA)为淬灭剂进行自由基淬灭实验,分析PFOA的降解机理。结果表明:Na2SO4电解质体系中,PFOA具有良好的降解效果;酸性条件下(pH为3~4.2)PFOA脱氟效果较佳,中性条件下较差,脱氟效果随初始浓度的增加而降低,随电流密度的增大先提升后趋于稳定。初始pH为3、电流密度30 mA·cm^-2、流速32.5 mL·min^-1、初始浓度100 mg·L^-1、Na2SO4浓度0.05 mol·L^-1条件下,电解180 min,PFOA脱氟率达53.45%,能耗约为1.13 kWh·(g F)-1;硫酸盐体系产生的·OH、SO-4·两种自由基均能氧化降解PFOA。

As a new persistent organic pollutant,perfluorooctanoic acid(PFOA)extremely stable in the environment,and resistant to most conventional biological and advanced oxidation treatment technologies.The electrochemical degradation of PFOA on boron-doped diamond(BDD)anodes and a stainless steel cathode was demonstrated.The defluorination of PFOA in different electrolyte systems was compared.The main reaction conditions on defluorination of PFOA on BDD anodes were investigated,including initial pH value,flow rate,current density,initial PFOA concentration,and electrolyte concentration.The energy consumption of electrochemical degradation of PFOA was estimated.Radical quenching experiments were performed with methanol(MeOH)and tert-butanol(TBA)as quenchers to analyze the degradation mechanism of PFOA.The results revealed that the degradation effect of PFOA was significant in Na2SO4 electrolyte.The degradation of PFOA was much better in acidic(pH=3~4.2)solution and worse in neutral solution.The defluorination decreased with increasing initial concentration,and increased with increasing current density until invariant.The defluorination rate of PFOA on BDD anodes achieved 53.45%and the energy consumption was estimated as 1.13 kWh·(g F)-1 after 180 min electrolysis at initial pH=3 at a constant current density of 30 mA·cm^-2 at an initial 100 mg·L^-1 PFOA concentration with a flowrate of 32.5 mL·min^-1 in a 0.05 mol·L^-1 Na2SO4 electrolyte solution.In addition,the results proved that both·OH and SO-4·radicals generated at sulfate electrolyte were responsible for PFOA oxidation on BDD electrodes.