The behaviour of silica in gold cyanide solutions

Silica sand was found to adsorb significant amounts of gold cyanide, and has shown a higher gold loading per surface area than for activated carbon. The solubility of silica was strongly related to pH, especially in a highly alkaline environment. The solubility was relatively slow and equilibrium conditions were attained after a few weeks. Infrared tests confirmed the presence of Au(CN)(2)(-) on the surface of the silica sand. A fire assay showed that the gold adsorbed onto silica, and did not merely attach physically to the surface. Thermal treatment modified the silanol groups on the surface of the silica, which made it practically inert towards gold adsorption. (C) 1997 Elsevier Science B.V.