砷化氢析出电势的探讨

Evolution potential of arsine

据热力学参数 ,计算得到砷酸、亚砷酸、单质砷析出砷化氢的标准平衡电势值分别为 0 .1 44V ,0 .0 0 5V ,- 0 .2 38V。在铜电解液净化工序中 ,砷酸优先于亚砷酸析出砷化氢 ,当阴极电势足够负时 ,三者共同放电析出砷化氢。计算结果与实测结果基本吻合 ,均表明砷化氢析出的标准平衡电势值正于 - 0 .60 8V。在铜净液工序中 ,采用控制阴极电势脱铜脱砷电积法 ,能有效抑制砷化氢的析出。

The standard equilibrium potentials of evolving AsH 3 from arsenic acid, arsenious acid and element arsenic are thermodynamically calculated as 0.144 V, 0.005 V, -0.238 V respectively. In the processing of the purification of copper electrolyte, arsenic acid prior to arsenious acid evolves AsH 3. When cathodic potential is negative enough, arsenic acid, arsenious acid and element arsenic co discharge and AsH 3 is evolved. The results of thermodynamical calculation are basically concordance with the measured results. The standard equilibrium potential of AsH 3 evolution is absolutely more positive than -0.608 V. In the processing of the purification of copper electrolyte, the separation of copper and arsenic by electrowinning of controlling cathodic potential can prevent AsH 3 from evolving effectively.