CHEMICAL STABILITY OF LEACH RESIDUES AFTER BROMINATION

摘要

In the past, considerable work has been done on the applicability of bromine chemistry in the extractive metallurgy of gold. While the research in this area spanned from the understanding of fundamental dissolution chemistry to the demonstration on a pilot plant scale, no work was done on the fate of discarded leach residues with respect to the stability of accompanied heavy metals. Because the leach residues were the discharge products of halide/halogen system, the general perception was the contained heavy metals would be more susceptible to dissolution than in typical sulfate systems, thus causing increased environmental problems. A long-term study was performed to obtain the information on the stability of heavy metals contained in the leaching residues after bromination. The study involved the leach residues of three different ores, as well the precipitates prepared from the synthetic solutions (not presented here). The conclusion of this study is that the stability of solid residues produced by bromination leaching was same as the stability of leach residues produced by leaching in the sulfate systems. Also, contrary to the past expectations, the presence of bromide ions in the test solutions (up to 1 g/L NaBr) did not enhance the solubility of heavy metals (Cu, Zn, Pb, As) beyond the solubilities found in the sulfate systems.