Fouling effect of different flotation and dewatering reagents on activated carbon and sorption kinetics of gold

Abstract

In carbon-in-pulp and carbon-in-leach circuits, among different organic and inorganic compounds present in the gold cyanide solution, flotation reagents play the main role in the fouling of activated carbon. In this study the effects of different types and variable concentrations of flotation and dewatering reagents on the kinetics of gold sorption onto granular activated carbon (GAC) were evaluated on the basis of kinetic rate constant (i.e., k value) of an empirical rate equation. The lower the k value, the greater is the fouling effect. It was observed that the k value rapidly decreases by increasing the concentration of collectors including potassium isobutyl xanthate (PIBX) and potassium ethyl xanthate (PEX) up to 20 mg/L and at higher concentrations, the k value gradually leveled off to 53 h − 1 for PIBX, which is 46% lower than the 99 h − 1 for PEX. At low concentrations (i.e., up to 15 mg/L) of methyl isobutyl carbinol, the k value gradually reduced and at higher concentrations, the decrease is found to be more pronounced. The fouling effect of flocculant was negligible and it would be even insignificant at high concentrations. The combinational effect of flotation reagents on the kinetic activity of GAC towards gold sorption was synergistically better. The cumulative adsorption of flotation reagents onto GAC in a continuous circuit within 28 days resulted in 40% decrease of k value, although it was still above admissible limit of 80–100 h − 1 .