TOXICITY OF ARSENIC DURING HIGH-TEMPERATURE BIOLEACHING OF GOLD-BEARING ARSENICAL PYRITE

A moderately thermophilic mixed culture, MT, and the thermophilic Sulf olobus acidocaldarius strain BC were studied for their response to ars enic in a defined medium and also in media containing a pyrite and an arsenical pyrite flotation concentrate. In defined medium, the individ ual constituents of the MT culture exhibited a high tolerance to arsen ite and arsenate compared to S. acidocaldarius strain BC. When grown o n increasing concentrations of the pyrite flotation concentrate, both cultures had similar specific leaching rates over the various concentr ations of the mineral substrate. In contrast, S. acidocaldarius strain BC exhibited a decreasing specific teaching rate when grown on the ar senical pyrite while the MT culture was not affected. In addition, ars enic added to cultures of S. acidocaldarius strain BC growing with pyr ite as a growth substrate inhibited further growth, while added arseni c had no effect on the MT culture growing on the pyrite. These data in dicate that the moderately thermophilic, arsenic-resistant MT culture was able to leach arsenical pyrite more efficiently than was the S. ac idocaldarius strain BC culture at high concentrations of the mineral. This emphasizes the fact that proper culture selection is an important parameter when developing commercial processes involving arsenic-cont aining minerals.