Studies of pentlandite leaching in mixed oxygenated acidic chloride-sulfate solutions

The kinetics and mechanism of pentlandite leaching in aerated acidic chlori de/sulfate solutions were studied using electrochemical and chemical techni ques. The electrochemical experiments showed that pentlandite experiences p assivation at low overpotentials. These results were consistent with the le aching studies which showed that pentlandite leaching proceeds at a low rat e. However, the addition of chloride ions was found to increase the leachin g rate, and it is believed that the role of chloride is to allow the format ion of a more porous sulfur product. Both temperature and oxygen partial pr essure had a substantial effect on the reaction rate, with optimum leaching kinetics being obtained at 85 degrees C and an oxygen pressure of 1 arm. U nder such conditions, 96% nickel extraction could be achieved during leachi ng in the presence of chloride ions. (C) 2000 Elsevier Science B.V. All rig hts reserved.