Use of chlorination in gold extraction as a nonpolluting alternative

M. OJEDA , E. PERINO, M. DEL C. RUIZ

Advances in Cleaner Technologies for the Mining and Metallurgical Industry

Editors: M. Sánchez, A. Valenzuela, E. Chaparro, A. Reghezza and J. Álvarez, University of Conception

Lugar: Chile; Año: 2008; p. 267 - 279

The recovery of gold, which has been a reason for intense research as a result of its great demand, makes interesting the treatment of auriferous raw materials of low grade and materials of refractory nature. In addition, there is a continuous search for the optimization of processes already established. The improvements achieved in the recovery of this noble metal tend to be reflected in the economic and environmental aspects, especially in relation to gaseous emissions and liquid effluents produced in gold recovery industries. Although amalgamation and cyanidation are efficient processes for gold recovery, they have the disadvantage of significantly contributing to the environmental contamination. For this reason, an increasing interest to develop new and alternative processes has been generated. Among these methodologies, chlorination is considered a potentially attractive process for gold recovery. In this work, the characterization and chlorination of a material from an auriferous alluvial deposit in the Province of San Luis (Argentina) were studied. The samples collected presented low gold concentrations due to the repeated exploitation works carried out in the zone by several private companies. For this reason, mechanical-physical concentration treatments followed by the addition of determined amounts of gold and the sample homogenization were carried out. The material obtained was characterized and used in chlorination tests. X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electronic microscopy (SEM) techniques were used for the characterization. The chlorination was performed by means of a pyrometallurgical process, using gas chlorine as reactive agent. Working times and temperatures were analysed. The results showed that gold chlorination begins at 350°C, with significant extractions at 500°C and 60 minutes, with a low attack of the matrix. The corrosion undergone by dispersed gold particles in the mineral were observed using SEM micrographs.