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Bacterial oxidation of a pyrite-arsenopyrite-gold ore concentrate was carried out in 14 l continuous-flow stirred tank reactors. Oxygen and carbon dioxide consumption rates, mineral dissolution rates and bacterial concentrations were measured at various steady-state residence times and with 6, 11 and 16 wt.% solids in the feed slurry. Mineral oxidation was found to be strongly dependant on bacterial activity. Arsenopyrite was found to be preferentially oxidised at the higher pulp densities., Bacterial oxidation of a pyrite-arsenopyrite-gold ore concentrate was carried out in 14 l continuous-flow stirred tank reactors. Oxygen and carbon dioxide consumption rates, mineral dissolution rates and bacterial concentrations were measured at various steady-state residence times and with 6, 11 and 16 wt.% solids in the feed slurry. Mineral oxidation was found to be strongly dependant on bacterial activity. Arsenopyrite was found to be preferentially oxidised at the higher pulp densities.

Bacterial oxidation of an arsenopyritic gold-ore concentrate was carried out with continuous-flow operation in 14 l, mechanically agitated reactors. Samples from the slurry reactors were separated into solid and liquid fractions and analysed separately to determine the electrochemical rates of sulphide conversion by the bacteria and the rates of direct bacterial oxidation of sulphide. The rates of the individual mechanisms are compared to the overall rates of biooxidation in the continuous-flow slurry reactors. The results show that the commonly hypothesised direct and indirect mechanisms of biooxidation both play a significant role in the bacterial oxidation of sulphide ores., Bacterial oxidation of an arsenopyritic gold-ore concentrate was carried out with continuous-flow operation in 14 l, mechanically agitated reactors. Samples from the slurry reactors were separated into solid and liquid fractions and analysed separately to determine the electrochemical rates of sulphide conversion by the bacteria and the rates of direct bacterial oxidation of sulphide. The rates of the individual mechanisms are compared to the overall rates of biooxidation in the continuous-flow slurry reactors. The results show that the commonly hypothesised direct and indirect mechanisms of biooxidation both play a significant role in the bacterial oxidation of sulphide ores.