二氧化氯对过量硫代硫酸钠氧化的动力学

为研究过量硫代硫酸钠与ClO2的反应动力学及其机理,采用停流技术测定该反应过程中各物质的浓度变化.结果表明,该化学反应方程式为:3S2O32-+2ClO2+H2O→S4O62-+2SO42-+2Cl-+2H+,建立相应的反应动力学方程,该反应对于ClO2和硫代硫酸钠均为一级,对S4O62-为0.5级,获取pH=9.27、T=298K和[S2O32-]0/[ClO2]0浓度范围为1.2～3.7情况下该反应的速率常数k值为2.8251×105L1.5/(mol1.5.s),反应活化能Ea为20.5kJ/mol,表明在一般的水处理研究中,硫代硫酸钠作为ClO2的猝灭剂是合理的,提出过量硫代硫酸钠与ClO2的4步反应机理,指出S2O3ClO22-是反应中重要的中间体,说明该反应遵循单电子转移机理.

Kinetics of excess thiosulfate oxidation with chlorine dioxide

Kinetics and mechanism of the reaction between excess thiosulfate and ClO2were studied by following the concentration change of reactive substances with the stopped-flow technique. Results showed that the stoichemistry was found to be 3S2O32-+2ClO2+H2O→S4O62-+2SO42-+2Cl-+2H+. The equation of reaction kinetics was established. The reaction was first-order with respect to both ClO2 and thiosulfate,and half-order to tetrathionate. When pH was 9.27,water temperature was 298 K and ratio of [S2O32-]0/[ClO2]0 ranged from 1.2 to 3.7,the order reaction rate constant k was 2.8251×105 L1.5/(mol1.5·s),and the reaction activation energy was 20.5 kJ/mol,which reveals that taking thiosulfate as the fast terminating reagent of ClO2 is reasonable under usual water treatment conditions. A 4-step mechanism based on the theory of single electron transfer(SET) between excess thiosulfate and ClO2 is proposed,in which S2O3ClO22-plays a significant role.