电化学法降解硫氰离子的机理及动力学

Mechanism and kinetics of thiocyanate removal by electrochemical method

采用电化学法降解硫氰离子。结果表明,当电流密度为40A/m^2、硫氰离子初始浓度为3.45mmol/L、pH值为3、反应时间为2h时,硫氰离子的去除率为80.2%;反应的主要产物为SO4^2-和CN^-;硫氰离子的电化学降解过程为阳极直接氧化过程。在低电流密度(10A/m^2)下,硫氰离子电化学降解前期为零级反应,后期为一级反应,限速步骤分别为阳极表面的电子转移和硫氰离子至阳极的传质;在高电流密度(200A/m^2)下,硫氰离子电化学降解为一级反应,硫氰离子至阳极的传质为限速步骤;当反应施加的电流密度大于极限电流时,继续增加电流密度,反应的表观反应速率常数没有明显上升。pH值对硫氰离子的降解影响并不显著;Fe^2+和Cl^-对硫氰离子的电化学降解过程均有消极影响。

Electrochemical method was used to remove thiocyanate.The results show that the removal rate of thiocyanate was 80.2% under the condition of current density of 40 A/m^2,initial thiocyanate concentration of 3.45mmol/L,pH value 3 and reaction time 2h.The main products of the reaction were SO4^2- and CN^-.At low current density(10 A/m^2),the electrochemical degradation of thiocyanate was zero order reaction in the early stage and first order reaction in the later stage with the speed-limiting steps of electron transfer and mass transfer,respectively.At high current density(200 A/m^2),the electrochemical degradation of thiocyanate was a first order reaction,and the mass transfer was the ratelimiting step.pH value had no significant effect on the degradation of thiocyanate.Fe^2+ and Cl^- had negative effects on the electrochemical degradation of thiocyanate.