隔膜电解法制备氯金酸及其机理探究

以金为阳极、石墨为阴极、饱和甘汞电极为参比电极、盐酸溶液为电解质,采用离子膜电解法制备了氯金酸。探究了制备过程中金的阳极行为以及实验条件氯离子浓度、pH、双氧水含量对制备过程的影响,并对反应机理进行了分析探究。结果表明：实验所得样品化学式为HAuCl₄.4H₂O,实验过程中基本上无金的损失,产率可达94%以上；电化学测试表明,金被电解为Au₃₊^发生在0.8-1.3V之间,致钝电压为1.3V；在pH为1.0的情况下最佳制备条件为电解电压1.25V,双氧水加入量5mmol,；在电解过程中减小电解液pH、增大电解液中氯离子浓度可以促进金的电解,此外峰电位随着pH的减小而降低；奈奎斯特图表明制备过程受电荷转移与扩散混合控制,随着溶液中Cl_-^{浓度的增大与双氧水的加入},扩散控制影响减弱由混合控制向电荷转移控制过渡。与传统工艺比较,隔膜电解法制备氯金酸具有无污染、易操作、安全性高、盐酸损失小等优点。关键词：氯金酸；电解法；金；盐酸中图分类号：TG146 文献标识码： A 文章编号：1003-5214 (2020) 01-0000-00

Preparation of chloroauric acid by diaphragm electrolysis

Chloroauric acid was prepared by ion-exchange membrane electrolysis with gold as anode, graphite as cathode, saturated calomel electrode as reference electrode and hydrochloric acid solution as electrolyte. The anodic behavior of gold in the preparation process and the effects of experimental conditions such as chloride ion concentration, pH and hydrogen peroxide content on the preparation process were explored, and the reaction mechanism was analyzed and explored. The results show that the chemical formula of the sample obtained in the experiment is HAuCl4 ? 4H2O. There is basically no loss of gold in the process of the experiment, and the yield can reach more than 94%; Electrochemical tests showed that the electrolysis of gold to au3+ occurred between 0.8-1.3v, and the passivation voltage was 1.3V; Under the condition of pH 1.0, the best preparation conditions are electrolytic voltage 1.25V, hydrogen peroxide dosage 5mmol,; In the process of electrolysis, reducing the pH of electrolyte and increasing the concentration of chloride ion in electrolyte can promote the electrolysis of gold. In addition, the peak potential decreases with the decrease of pH; Nyquist diagram shows that the preparation process is controlled by charge transfer and diffusion mixing. With the increase of cl- concentration in the solution and the addition of hydrogen peroxide, the influence of diffusion control weakens, and the transition from mixing control to charge transfer control. Compared with the traditional process, the preparation of chloroauric acid by diaphragm electrolysis has the advantages of no pollution, easy operation, high safety and small hydrochloric acid loss.