ADSORPTION OF CYANIDE COMPLEXES ONTO ACTIVATED CARBON

Experiments have been carried out to study the adsorption of gold from a cyanide solution on extruded activated carbon. The adsorption of gold complexes depends on initial gold complex concentration, temperature, carbon mesh size, carbon amount, mixing speed and gases in contact with the solution. Experimental data are in agreement with the Freundlich adsorption isotherm. The equilibrium and adsorption rate are affected by some chemical species present in solution: cyanide complexes of Ag, Cu, Fe, ions like CN-, H+, Ca2+ and organic solvents (ethyl alcohool and Potassium Amyl Xanthate: AXK). The mechanism of adsorption on activated carbon can be written in three steps: diffusion from the bulk of solution to the particule surface, diffusion inside the pores of extruded particules and adsorption on the active sites of carbon. The activated carbon samples treated with aqueous solutions containing a sodium dicyanoaurate complex have been analyzed by X-rays fluorescence, electronic microscopy and zeta potential analysis, this analysis suggests that the gold complex is adsorbed on the activated carbon without any change in the molecular structure of the gold complex.