Gold recovery from cyanide-starved glycine solutions in the presence of Cu using a molecularly imprinted resin (IXOS-AuC)

The synergistic leaching system using glycine as the main lixiviant with low levels of cyanide as a catalyst has been shown to be an effective approach to leach gold-copper ores and concentrates, allowing the consumption of cyanide to be remarkably reduced. The recovery of gold from the synthetic cyanide-starved glycine leachate in the presence of copper has been investigated using. It was found that the adsorbed copper was mostly cuprous cyanide. The effects of [CN-]:[Cu-T] and [Gly]: [CUT] molar ratios were not significant on the adsorption of gold and copper using IXOS-AuC resin. The gold recovery increased, while the copper recovery decreased with the increasing initial gold concentration. The equilibrium and kinetics studies were undertaken, and the experimental adsorption equilibrium and rate data showed an excellent fit using the Freundlich isotherm and pseudosecond-order models respectively. Elution tests showed that the loaded copper can be selectively pre-eluted over gold by 0.4 M NaCN at pH 11.5. Gold can be effectively eluted by either acidic thiourea or alkaline thiocyanate. The multi-cycle adsorption/elution tests showed that the resin can be effectively regenerated by both acidic thiourea and alkaline thiocyanate, with an insignificant decrease in adsorption and elution efficiency over 3 adsorption/elution cycles. From SEM analysis, the change of surface morphology of the resin was not significant after adsorption and the adsorption/elution cycles.