毛细管电泳用于S_4O_6^(2-)碱性水解反应动力学研究

Kinetic Study of Hydrolysis of Tetrathionate Under Basic Conditions Using Capillary Electrophoresis

连四硫酸根离子S_4O_6^(2-)是硫代硫酸根离子S_2O_3^(2-)氧化过程中的中间产物,常存在于湿法浸金溶液中或废弃定影剂中。S_4O_6^(2-)在碱性环境中,会发生自身的碱性水解,生成S_2O_3^(2-)、S_2O_6^(2-)、S_3O_6^(2-)和S_5O_6^(2-)等,反应过程十分复杂。本研究应用毛细管电泳方法对水解反应过程中的硫氧化合物进行实时定性与定量监测,该反应计量方程为4S_4O_6^(2-)+8OH-→6S_2O_3^(2-)+S_3O_6^(2-)+SO_4^(2-)+4H_2O,反应的终产物有S_2O_3^(2-)、S_3O_6^(2-)和SO_4^(2-)。水解速率强烈依赖于反应的pH值,通过计算得到水解反应在pH值10.5~12.0之间对于两种反应物的反应级数均为1,平均反应速率常数为0.115 M^(-1)s^(-1)。不同于前人的研究结果,本研究中发现S_2O_3^(2-)对S_4O_6^(2-)的水解反应并未产生明显的催化作用。

Tetrathionate（S4O6^2-） is one of the intermediates in the oxidation of thiosulfate（S2O3^2-）,which often exists in the leaching solution of gold and spent fixing solution.The hydrolysis of S4O6^2- under basic conditions produces S2O3^2-,S2 O2-6,S3O6^2- and S5 O2-6,etc,which is indicating the complexity of the reaction.In this investigation,capillary electrophoresis was used to identify the sulfur-oxygen species in the reaction solutions.Qulitative and quantitative analyses were carried out for the species to explore the kinetic behavior of the tetrathionate hydrolysis reaction.The stoichiometric equation was 4S4O6^2-＋8OH-→6 S2O3^2-＋ S3O6^2-＋ SO4^2-＋4H2O,with S2O3^2-,S3O6^2- and SO4^2- as the final products.In the range of pH 10.5~12.0,the reaction was first order with respect to each of the reactants,with average reaction constant 0.115 M^（-1）s^（-1）.No obvious catalytic effects were found for the concentration of S2O3^2- on the hydrolysis of S4O6^2-,which was different with previous report.