漂白过程的电化学研究——Ⅰ、Fe(Ⅲ)EDTA氧化金属银的反应动力学

ELECTROCHEMICAL STUDIES ON THE BLEACHING PROCESS Ⅰ. THE KINETICS OF THE REACTION BETWEEN Fe (Ⅲ)EDTA AND SILVER

在卤离子存在下,Fe(Ⅲ)络合物与金属银之间的氧化还原反应,可用氧化形成的卤化银的电化学还原时间τ进行测定。本工作用银旋转圆盘电极研究了在改变氧化时间,反应物浓度和电极旋转速度的情况下,Fe(Ⅲ)络合物与金属银之间反应动力学,并测定了形成溴化银的初始速率与pH的关系。 该氧化还原反应是扩散控制反应,对于Fe(Ⅲ)EDTA和卤离子来说均为一级反应。Fe(Ⅲ)EDTA在水溶液中的扩散系数可由极限电流与Fe(Ⅲ)EDTA的浓度和银旋转圆盘电极的旋转速度的平方根之间的关系求算出来。

The silver rotating disc electrode was used to study the redox reaction:Fe(Ⅲ)-complex + Ag° + X-→ Fe(Ⅱ)-complex + AgXThe redox reaction could be followed by galvanostatic reduction of AgX. The galvanostatic reduction time (TTTTTTTTTT) can easily be determined because of the jump at the end of the reduction of the silver halide. The kinetics of the reaction between Fe(Ⅲ)-complex and silver electrode in the presence of halide would be studied varing oxidation time, the concentration of the reactants and the rotation frequency of silver disc electrode.The redox reaction is a diffusion controlled reaction and is first order with respect to the Fe(Ⅲ)-complex and halide respectively. The initial rate of formation of silver bromide decreases with increasing pH.The diffusion coefficient of Fe(Ⅲ)EDTA was determined from the dependence of the limiting current on both the concentration of Fe(Ⅲ)-complex and square root of the rotation frequency of silver disc electrode.