Grafting of organic sulfur-containing functional groups on activated carbon for gold(I) adsorption from thiosulfate solution

Abstract

In the present study, sulfur-containing functional groups were grafted onto activated carbon and adsorption behavior for [Au(S2O3)2]3− was studied. Activated carbon grafted with sulfur-containing functional groups (S-AC) was developed with MBT (2-Mercaptobenzothiazole). The effects of MBT dosage and contact time in the preparation process were optimized; solution pH, thiosulfate ion concentration, and temperature of the surroundings in the adsorption stage over gold adsorption were studied. With a contact time of 24 h and MBT dosage of 0.7 g, S-AC had better gold adsorption ability and the prepared adsorbents worked well at a pH of about 9.0 and thiosulfate concentration of about 0.1 mol/L. The Freundlich model and pseudo-second order kinetics model fit the [Au(S2O3)2]3− adsorption process well. A total gold amount of 18.402 kg/t for five stages was attained with S-AC. The presence of thiol and disulfide linkages on the surface of activated carbon was proved using XPS, FT-IR, BET, and SEM. The adsorption of [Au(S2O3)2]3− onto S-AC involved a gold(I) thiolate and disulfide interchange mechanism. This study made the adsorption of [Au(S2O3)2]3− on activated carbon possible via a simple and feasible method, and this is of great significance for future research in leaching gold with thiosulfate.