FACTORS AFFECTING THE ELUTION OF GOLD CYANIDE FROM ACTIVATED CARBON

Functional relationships were determined between the effects of pH, temperature, and the concentrations of cyanide and cations on the gold cyanide equilibrium during elution from activated carbon in columns and in batch reactors. Although the parameters in these functional relationships will differ for different types of activated carbon and for different conditions of pre-treatment, the form of the relationships would remain unchanged. Such a multi-parameter equilibrium expression can be incorporated into a dynamic model describing a continuous shift in the adsorption/desorption equilibrium as elution proceeds. The elution of gold cyanide is suppressed by the presence of cations (M(n+)) through the formation of M(n+) (Au(CN)2-)n on the carbon. The horizontal position of the gold peak in an AARL elution profile was found to be a function of the elution of the cations from the carbon bed. High temperatures and intense cyanide pre-treatment, i.e. conditions favourable for desorption, decreased the sensitivity of gold elution to flow rate and the radial distribution of the gold through the carbon particles. This implies that the resistance to mass transfer was less profound under strong elution conditions.