Thiourea Leaching Of Gold-Bearing Mine Wastes From The Madjarovo Processing Plant In The South East Of Bulgaria

Abstract

The study presented in this paper deals with the issues concerned with the utilisation of floatation tailings produced in the past by plants in which complex sulphide gold-bearing ore was processed. The concentration of gold and silver in the tailings is found to be sufficiently high to justify starting a research programme for their recovery. A number of studies have shown that thiourea has potential for such treatment — treatment which is not amenable to cyanidation of ores or where environmental concerns make the use of cyanide compounds problematic.

The choice of thiourea in this research was motivated both by enviroumental and technological considerations. The region in question is environmentally sensitive because it is a border region of Bulgaria, and also because the Arda River, which is a major source of water supply, runs through the region. The impetus for the research was provided by the fact that the relatively high content of sulphides as a potential cyanide-consuming mineraI is considered a major technological drawback necessitating the use of an alternative lixivant such as thiourea.

A technical now-sheet, developed for the recovery of gold and silver from mine tailings, is presented. It consists of the following operations: magnetic separation, floatation, hydrochloric leaching, and thiourea leaching. The purpose of hydrochloric leaching is to provide the oxidant required for the next stage of thiourea leaching and to expose the surfaces of the gold particles for further processing.

The method presented is typical of how suitable technologies could be developed for recovering valuable materials from potentially harmful wastes for reuse and/or recycling. It is argued that due attention should be paid to such technologies for reinforcing efforts at sustainable solid waste management.