Electrochemical Study of Redox Reaction of Various Gold III Chloride Concentrations in Acidic Solution

Abstract

The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl 3 in various concentrations thus 30 and 60 mg/L AuCl 3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl 3 , respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl 3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl 3 in acid solutions. The reaction between AuCl 3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of AuCl - 4 on the surface of the working electrode at the reduction site for each AuCl 3 concentration using Nernst equation was 1.22 × 10 9 ppm and 2.44 × 10 9 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.