Evaluation of a cleaner production for cyanide tailings by chlorination thermal treatments

Abstract

This paper describes cleaner chlorination thermal treatment for the recovery of gold from waste materials generated in gold manufacturing. Chlorination thermal treatment was conducted, and thermogravimetric-mass spectrometry (TG-MS) analyses were performed on the cyanide tailings (CTs). The results, along with thermodynamic calculations performed using FactSage, showed that Cl2 was the main compound participating in the chlorination reaction, and almost no HCl was generated. The recovery mechanism of gold was explored by studying the influence of roasting temperature on changes in contents of Au, Cl, S and the phase composition. The results showed that the gold was not recovered simultaneously from different carriers in the slag, but was instead recovered successively according to the degree of wrapping. Under the best conditions, roasting CTs with 5 wt% CaCl2 at 1273 K yielded close to 90 wt% gold recovery. A toxicity analysis showed that the pollution risk posed by the roasted CTs was eliminated as much as possible, as the cyanide content in the roasted slag was only 0.77 vol% of that of the raw material, which further meets the national emission standards. In a word, clean-roasted CTs can greatly reduce the pollution control costs for a factory.