Effect of Tin Ion on Electrodeposition Behavior of Indium

Abstract

Electrorefining is an effective method for preparing high-purity indium. To realize the control of impurity Sn in crude indium electrolytic refining, electrochemical test methods, such as cyclic voltammetry (CV), and chronoamperometry (CA) were mainly used to study the electrochemical behavior of indium. The results show that when a few of SnSO4 was added to the electrolyte containing indium sulfate, in the meantime, the Sn2+ concentration reached 5000 ppm, in the electrolysis process, the impurity Sn in the cathode was appeared to precipitate before the indium precipitated. The electrodeposition of indium was irreversible, controlled by diffusion steps, and In3+ reduction was carried out by fractional steps, transferring one electron at a time. The diffusion coefficient of In3+ calculated by cyclic voltammetry was 1.02 × 10−7 cm2/s, and the average charge transfer coefficient was 0.081. The nucleation mechanism of indium conformed to three-dimensional instantaneous nucleation. The results provide theoretical guidance for electrolytic refining of crude indium and electrochemical regulation of impurities.

Keywords

• high purity indium
• cyclic voltammetry
• electrochemical behavior
• nucleation mechanism