Bioreactor Engineering for treating refractory gold-bearing concentrates: An Indian Experience

摘要

Biooxidation of refractory gold ores and concentrates provides a viable alternative to the conventional oxidation technologies due to its eco-friendliness and substantially lower costs. The Hutti Gold Mines Company, which is the largest producer of gold in India, is undergoing major expansion plans. Recent exploration has shown that the gold deposits are sulphidic in nature containing pyrite and arsenopyrite. These sulphide ores have to be oxidized in order to extract gold economically. The Indian Institute of Science and The Hutti Gold Mines Company have undertaken a joint programme to run a demonstration bioreactor for oxidation of refractory gold concentrates. As part of this joint programme, in the present study biooxidation of a sulphidic concentrate containing gold has been carried out in laboratory scale bioreactors using Thiobacillus ferrooxidans isolated from the mines to optimize the operating parameters. The effect of some of the experimental conditions in the bioreactor on the growth of the microorganisms has been evaluated. The air/CO_2 ratio along with the pulp density and temperature play a major role in determining the iron oxidation capability of Thiobacillus ferrooxidans. Results show that with biooxidation the gold recovery from the concentrate increased from 45% to above 85%. Similarly the silver recovery increased from 62% to 97%. This study demonstrates that biooxidation technology can be used for treating refractory gold concentrates successfully. Based on the results a detailed flowsheet has been developed for the demonstration bioreactor plant.