A combined two-step bioleaching process at moderately and extremely thermophilic temperatures

摘要

In this work a combined two-step bioleaching process has been investigated. In the first stage a moderately thermophilic culture was used followed by an extremely thermophilic culture, Sulfolobus in the second stage. It was found that the Sulfolobus metallicus culture survives higher arsenic concentrations than expected by the pre-oxidation at lower temperature. Thus, with this two-step combined bioleaching process it is possible to reduce the toxicity of the released arsenic and therefore use of higher pulp densities of the arsenic containing materials is possible. When subjected to cyanidation, a somewhat higher gold and silver grade was found in the residue from the concentrate ultimately oxidized by Sulfolobus in comparison with the residue from the moderately thermophilic treatment. However, cyanide consumption and thiocyanate formation was significantly lower with the extreme thermophile.