Kinetics of simultaneous recovering of Au and Ag from CTs by chloridizing volatilization methods

Abstract

Cyanide tailings (CTs), which amount to hundreds of millions of tons and pose significant a danger to the environment's ecology, are regarded as hazardous waste. This study suggests an efficient and environmentally favorable method for the recovery of gold and silver from CTs. The influence of calcium chloride dosage, silicon dioxide dosage, pellet moisture content, roasting temperature, and roasting duration on chloridizing volatilization of Au and Ag was investigated. The simultaneous recovery of gold and silver from cyanide tailings via heating with chlorination was also investigated. It was found that the calcium chloride dosage and temperature increase the chloridizing volatilization rates, while the silicon dioxide dosage and particle moisture content decrease it. The inter-diffusion through the gangue layer served as the rate-limiting phase in the chloridizing volatilization kinetics, which was based on the shrinking core model. The apparent activation energies (Ea) of 24.01 kJ•mol-1 (Au) and 24.62 kJ•mol-1 (Ag) are in agreement with this result. The orders of reaction corresponding to various values of temperature, moisture content, silicon dioxide, and calcium chloride dosages were also computed. Semi-empirical equations can be used to describe the rate of reaction in diffusion-controlled processes.