• Leaching and electrochemical behavior of gold in iodide solutions

      Hiskey, J. Brent; Qi, Peihao, 1957- (The University of Arizona., 1990)
      Of the halogens, the gold iodide complexes are the most stable in aqueous solutions. A series of experiments was performed to investigate the kinetics and mechanism of the leaching reaction between gold and iodide. Using a rotation disk technique, the most important kinetic parameters were measured. The reaction rate was found to be first order with respect toI⁻₃ and half order with respect to I⁻. A gold leaching rate of about 2.6 x 10⁻⁹ mol/cm²·sec for 10⁻² M I⁻ and 5 x 10⁻³ M I₂ was obtained. This value is close to that for typical cyanidation. The reaction rate appears to be controlled mainly by diffusion of reactants through the boundary layer of solution to the gold electrode under the conditions studied. The electrochemical study of gold in different halide solutions, with emphasis on iodide, was also carried out. The electrochemical techniques used in this investigation include cyclic voltammetry and linear sweep voltammetry. The results displayed the sequential oxidation for gold dissolution in iodide solution and confirmed that iodide has the strongest oxidation capability of dissolving gold of the halides.