Effect of solid loading on thermophilic bioleaching of sulfide minerals

Abstract

The effect of solid loading (mineral pulp density) on thermophilic bioleaching of pyrite by Sulfolobus metallicus (BC) was investigated in a batch reactor. Different mineral pulp densities in the range 3–18% (w/v) were tested. With mineral pulp densities ranging from 3 to 9% the bioleaching proceeded in a single stage with a relatively constant rate. The bioleaching rates calculated for pulp densities of 3, 6 and 9% were 0.10, 0.11 and 0.09 kg iron m−3 h−1 respectively. By contrast the bioleaching of pyrite at pulp densities of 12 and 15% proceeded in two distinct stages. During the exponential phase of microbial growth a sharp and linear increase in concentration of released iron was achieved. This increasing trend levelled off in the presence of non-growing cells and the second stage of bioleaching continued with a slower rate. For the pulp density of 12% the bioleaching rates of the first and the second stages were 0.09 and 0.02 kg iron m−3 h−1 respectively, whereas the calculated rates in the presence of 15% mineral were 0.07 and 0.017 kg iron m−3 h−1 for the first and the second stages. Application of 18% mineral adversely influenced the activity of the cells and the extent of bioleaching in this case was insignificant. © 2000 Society of Chemical Industry