A quantitative study into carbon-in-pulp adsorption operations

Abstract

Carbon-in-pulp (CIP) and carbon-in-leach (CIL) remain the most effective, and widely used processes for gold recovery from cyanided pulps. The extensive use of carbon in such processes have prompted many researchers to investigate the mechanism of metal cyanide adsorption. Not only has this provided many viable theories in the understanding of the mechanism, but it has also led to an improved understanding of the effects of the various operating conditions on the CIP circuit. However, the declining gold price has made gold producers aware of the need to either further optimise existing circuits or find alternative means of operation so as to improve efficiency. It is therefore the aim of this study to investigate the factors which influence the metal extraction circuit. In this study the effects of parameters such as gold and carbon concentrations, slurry density and stirring speed on the adsorption process were investigated. It was found that the effects of gold and carbon concentrations could be determined directly, that is, a definite linear relationship exists between these two parameters and adsorption rate. However, slurry density and stirring speed (power input) have a twofold effect on the process. For this reason two distinct terms called the "blinding" and "mixing" numbers have been identified. It has been shown that all the parameters investigated influences the rate of adsorption during the constant rate adsorption period. However, only solution concentration, carbon concentration and carbon loading influence the process during the diminishing rate of adsorption. This confirmed the belief that intraparticle diffusion is the rate controlling factor during the diminishing rate period. Furthermore, the point at which constant rate adsorption is replaced by the diminishing rate of adsorption is mainly a function of solution concentration.