Wastewater Treatment With Gold Recovery Through Adsorption By Activated Carbon

Abstract

The exploitation of gold mines of North Greece, which starts soon, and the continually increasing environmental concerns (leading to lower cyanide maximal permitted values in water), make the relative research of considerable interest. With respect to this, a refinement of the gold and silver recovery methods may contribute to cost minimisation of cyanide wastewater treatment. Several researchers have investigated the kinetics of the adsorption of gold and silver by activated carbon from cyanide, thiourea and chloride solutions. Very few works have been reported on gold adsorption by activated carbon from iodineliodide solutions which can be obtained as a downstream leach liquor in wastewater treatment. This work investigates the kinetics of adsorption of gold from iodine solution by activated carbon. It is proved that this kind of adsorption obeys the following kinetic equation: Cb=Co-(Co-Chf)[l-exp(-kt)], where Cb, Cint CO are the concentrations of gold species in the bulk solution at time t, 0, a, respectively. The values of the parameters CO, Cmf, k of this equation are estimated by means of non-linear least squares regression. The k-values estimated in different temperatures give (by similar non-linear regression) a region of activation energy values which indicate, at 95% confidence level, that the critical stage of the process is the diffusion of the gold species in the pores of the activated carbon.