Equilibrium shift of gold adsorption in a batch reactor

Abstract

Over the years the carbon-in-pulp technology has been refined to become the highly efficient process that is used in our present-day system of recovering dissolved gold from cyanide leached pulps. The efficiency of a CIP circuit mainly depends on the effectiveness ofthe adsorption section as it not only determines the amount of soluble gold lost in the residues, but also indirectly affects the function of the other processes in the plant. Research in this area has declined over the past few years as a result of a decrease in the gold price. It is now more than ever important to investigate the operating conditions ofthe adsorption process to ensure that a highly effective system is maintained.The adsorption of gold cyanide onto activated carbon is to a large extent dependent on maintaining operating conditions well above those of equilibrium. The Freundlich and the Langmuir isotherms have been used by many researchers to describe the equilibrium conditions of the adsorption process. The general practice in the carbonin- pulp technology is to use an isotherm for the prediction of a circuit's performance. As confidence has increased in the reliability of these predictions, it has become important to acquire knowledge of the equilibrium condition that is driving the process. Previous research findings have indicated that the equilibrium isotherm of gold cyanide adsorption onto activated carbon is influenced by changes in the adsorption conditions down the adsorption train. This equilibrium or isotherm shift may lead to errors in the prediction of gold adsorption rates, which results in the filct that the simulations of the performance of the CIP circuits are not reliable. In this study the aim was to investigate the combined influence of various operating conditions on the adsorption equilibrium