Adsorption of gold from cyanide leaching solution onto activated carbon originating from coconut shell—Optimization, kinetics and equilibrium studies

Abstract

This study investigates the behavior of gold adsorption from cyanide leaching solution onto activated coconut shell carbon. The experimental was designed according to CCD implemented with RSM and a quadratic model was developed for regression analysis. The effects of important parameters including pH, agitation rate, adsorbent concentration and adsorption time were studied to find the best operating conditions, and the optimized value of pH, agitation rate, activated carbon concentration and adsorption time was found to be 11, 40 rpm, 1.25 g/L and 3 h, respectively. Under these conditions, the adsorption rate was found to be about 87.11%. Also, the optimal conditions were established on industrial cyanide leaching solution and the results demonstrated that adsorption rate of gold could be obtained about 89.25%. Adsorption behavior was kinetically investigated using pseudo first-order and pseudo second-order models among which data were mostly correlated to pseudo first-order model. The further analysis of kinetics indicated that intra-particle diffusion was the rate-limiting step. Adsorbate–adsorbent interactions at 298 k was assessed by Langmuir, Freundlich, and Temkin isotherm models from which Freundlich model had the highest consistency with the experimental data.