Bioleaching of sphalerite by the acidophilic thermophile Acidianus brierleyi

The kinetics of leaching of sphalerite by the thermophilic Acidianus brierleyi were studied in a batch stirred reactor. Experiments were done at 65 degrees C and pH 2.0 on the adsorption of A. brierleyi onto sphalerite and the bioleaching of sphalerite particles, The distribution of A. cells between the mineral and solution was attained within the first 30 min of exposure to sphalerite, and the equilibrium distribution data were correlated with the Langmuir isotherm. The addition of 0.3 and 1.4 kg/m(3) ferric iron to the A. brierleyi culture resulted in a significant decline in the leaching rates, probably because of the formation of iron precipitates such as jarosite. Rate data collected in iron-free leach solutions were analyzed to determine microbial kinetic and stoichiometric parameters for the growth of A. brierleyi on sphalerite, These growth parameters demonstrated that the rate of bioleaching with the thermophilic A. brierleyi is about seven times that with the common leaching mesophile, Thiobacillus ferrooxidans. (C) 1998 Elsevier Science B.V.