Adsorption of gold from thiosulfate solutions with chemically modified activated carbon

Adsorption of the gold-thiosulfate complex ion (Au(S2O3)(2)(3-)) on silver ferrocyanide (AgFC)-impregnated activated carbon in aqueous solution has been studied in order to find an effectual adsorbent for the thiosulfate extracting gold from ores. This study was performed using AgFC-impregnated activated carbon (AC-Ag-R-FC: AC: activated carbon, Ag: silver nitrate, R: heating, FC: potassium ferrocyanide) and an artificial aqueous solution of Au(S2O3)(2)(3-). Gold-thiosulfate complex adsorption kinetics and isotherm studies were carried out at pH = 9.0 on modified materials. It has been also found that the adsorption fits the intraparticle diffusion and Freundlich isotherm well. In order to understand the adsorption mechanism, raw and modified materials were characterized by N-2 adsorption-desorption measurements at 77K, scanning electron microscopy and X-ray photoelectron spectroscopy. The maximum adsorption capability of Au(S2O3)(2)(3-) on AC-Ag-R-FC is 3.55kgt(-1). Clearly, the extraordinary adsorption capacity of AC for Au(S2O3)(2)(3-) offers a new approach to address challenging gold-thiosulfate complex separation and could promote the future development of thiosulfate leaching gold process.