A Study of the Electrodeposition of Gold Process in Iodine Leaching Solution

Abstract

This paper mainly discusses electrodeposition of gold from iodine leaching solution through single-factor testing and explores the influence of gold concentration in catholyte, mass fraction of iodine in anolyte, anolyte n(I2):n(I−), cell voltage, and electrolysis time on the percentage of gold deposition and coulombic efficiency. Moreover, a response surface methodology was adopted to study interactions among variables and influence on the percentage of gold deposition, with mass fraction of iodine in anolyte, anolyte n(I2):n(I−), and cell voltage as variable factors and percentage of gold deposition as the response value. The electrodeposition process was fitted via pseudo first-order kinetics and pseudo second-order kinetics. Finally, the free surface morphology of gold deposited on the cathode plate was observed by scanning electron microscope. Given the results, a principal effect relationship can be concluded between mass fraction of iodine in anolyte, anolyte n(I2):n(I−), cell voltage, and percentage of gold deposition, with cell voltage > anolyte n(I2):n(I−) > mass fraction of iodine in anolyte and a second-order regression equation obtained with percentage of gold deposition as the response value. The optimized process conditions were gold concentration in catholyte 20 mg/L, mass fraction of iodine in anolyte 0.59%, anolyte n(I2):n(I−) is 1:7.5, cell voltage 12.9 V, and electrolysis time 2 h. The average percentage of gold deposition of three confirmatory experiments was 96.43%, a figure very close to the predicted value of the model 97.76%, which proves that the quadratic polynomial model obtained by response surface methodology optimization is feasible and that the electrodeposition of gold process conforms to a pseudo second-order kinetic model. Au can be attached well to the cathode plate and the deposition layer is formed by granular grain accumulation.