Bioleaching of six nickel sulphide ores with differing mineralogies in stirred-tank reactors at 30 ?C

摘要

A bioleaching study was conducted with six nickel sulphide ores from different geographical locations across Canada. Mineralogical and chemical examination revealed considerable variability between the samples, particularly in the silicate phases. The ores contain 0.3 to 1% nickel, primarily in pentlandite and secondarily in pyrrhotite. Copper was present primarily in chalcopyrite, and cobalt in pentlandite. The ores were subjected to the same crushing and grinding procedure, and bioleached under the same conditions for three weeks with a mixed culture of iron- and sulphur-oxidizing bacteria. Stirred-tank experiments with finely ground ore (-147 μm) at 30 °C were conducted to assess the effect of pH (2 to 5) and the impact of the bacteria. In general, the presence of the bacteria resulted in a statistically significant increase in nickel, cobalt, and copper extraction, and oxidation-reduction potential; whereas their presence resulted in a statistically significant decrease in acid consumption. Nickel extraction from pentlandite and pyrrhotite during bioleaching at pH 2 and 3 was generally good (49 to 86% after three weeks). All six ores showed a similar response to a change in pH; an increase in pH from 2 to 3 resulted in approximately the same nickel and cobalt extraction (within statistical error), and a statistically significant reduction in sulphuric acid consumption.