FACTORS INFLUENCING THE ADSORPTION OF GOLD-IODIDE ONTO ACTIVATED CARBON

Activated carbon has found increasing application during the past decade as an adsorbent for gold from cyanide leached pulps. As result of practical and theoretical advancements in recent years, the carbon-in-pulp (CIP) process has become the preferred method for gold extraction from cyanided slurries. Lately, environmental considerations have led to the investigation of alternative leaching processes. One group of lixiviants studied is the halogens, such as bromine, chlorine, and iodine. It is the aim of this paper to investigate the factors influencing the adsorption of gold from iodide solutions onto a coconut-shell-type activated carbon. Equilibrium loadings on the carbon indicated clearly that gold-iodide has a higher loading profile than has gold cyanide. The Freundlich isotherm fitted the equilibrium curve for gold-iodide adsorption on carbon. The experimental results indicated that the pH level, iodide, and dissolved oxygen concentration had little or no influence on the kinetic and equilibrium parameters in a film diffusion model. However, the initial gold, iodine, and tri-iodide concentrations altered both the rate and equilibrium of gold-iodide adsorption significantly. Scanning electron microscopy showed that elemental gold deposited on the carbon surface influences the high film transfer coefficients obtained for gold-iodide adsorption.