ADSORPTION OF GOLD AND PALLADIUM FROM CYANIDE SOLUTIONS USING ACTIVATED CARBON AND ION EXCHANGE RESINS

摘要

The recovery of gold and palladium from cyanide solutions by use of activated carbon and ion exchange resins has been investigated in the laboratory. The kinetics of adsorption were determined using batch testing. The mechanism of adsorption was also studied using scanning electron microscopy and X-ray photoelectron spectroscopy. Initial work using synthetic solutions showed that both gold and palladium are readily removed from solution using activated carbon, and strong and weak base anion exchange resins. When gold and palladium were both present, there was a slight decrease in the rate of gold adsorption onto activated carbon and the weak base resin, whereas for the strong base resin there was no change. For palladium adsorption, the rate in the early stages increased for all three adsorbers. The final recovery, however, was significantly reduced for activated carbon, reduced slightly for the weak base resin, with no difference being noted for the strong base resin. Sectioned samples of carbon and the strong base resin onto which gold and palladium had been adsorbed for set times were examined using scanning electron microscopy to determine the profile of gold and palladium through the particle. It is postulated that adsorption is initially controlled by film diffusion. As adsorption continues particle diffusion becomes increasingly important. X-ray photoelectron spectroscopy studies were conducted to determine the adsorbed species. For gold, a combination of Au(CN)_2~- and AuCN, while only Au(CN)_2~- is adsorbed onto the resin. The palladium complex adsorbed is thought to be Pd(CN)_4~-.