锌电积体系Zn-MnO_(2)同槽电解电化学分析

Electrochemical analysis of the simultaneous electrolysis of zinc and manganese dioxide in zinc electrowinning system

基于循环伏安法、线性伏安法和电化学交流阻抗谱等分析测试并结合电解实验,系统解析了Zn-MnO_(2)同槽电解的电化学过程。研究结果表明:体系中Zn^(2+)的还原和Mn^(2+)的氧化在Mn^(2+)浓度低于10 g/L时互不干扰;Mn^(2+)的电氧化过程受电极界面钝化影响,提高Mn^(2+)浓度对同槽电解有利,但Mn^(2+)浓度过高会使氧化性MnO_(4)^(-)生成量增多,导致阴极Zn被化学氧化溶解;升高体系温度能改善Zn-MnO_(2)同槽电解效果,但过高的电解温度(≥80℃)会加速Zn的腐蚀。较优的Zn-MnO_(2)同槽电解条件为:Mn^(2+)浓度为10 g/L,阴阳极电流密度分别为40 mA/cm^(2)和10 mA/cm^(2),电解温度为60℃。该条件下,阴阳极电流效率分别为94.81%和12.16%,吨锌能耗为2456.58 kW·h,阳极产物为ε-MnO_(2)。

In this work,the electrochemical process of the simultaneous electrolysis of zinc and manganese dioxide was systematically analyzed based on cyclic voltammetry,linear voltammetry,and electrochemical impedance spectroscopy,combined with electrolytic experiments.The results show that the reduction of Zn^(2+)and the oxidation of Mn^(2+)in the system do not interfere with each other within a Mn^(2+)concentration lower than 10 g/L.Increasing the concentration of Mn^(2+)is beneficial for electrolysis in the same cell.However,if the concentration of Mn^(2+)is too high,it will increase the generation of oxidizing MnO_(4)^(-),leading to the dissolution of cathode Zn by chemical oxidation;The electro-oxidation process of Mn^(2+)is affected by the passivation of the electrode interface.Increasing the concentration of Mn^(2+)is favorable to the same groove electrolysis.However,an over-high concentration of Mn^(2+)will increase the production of oxidative MnO_(4)^(-),resulting in the dissolution of the cathode Zn by the chemical oxidation.In addition,increasing the deposition temperature can improve the same groove electrolysis performance of Zn-MnO_(2),but an excessively high temperature(≥80℃)will accelerate the corrosion of Zn.The optimal conditions of same groove electrolysis of Zn and MnO_(2) are as follows:Mn^(2+)concentration is 10 g/L,with a cathode current density of 40 mA/cm^(2) and an anode current density of 10 mA/cm^(2),respectively,at a temperature of 60℃.In the optimal conditions,cathode and anode current efficiencies are 94.81%and 12.16%,respectively.The energy consumption per ton of zinc is 2456.58 kW·h,and the anodic product isε-MnO_(2).