Oxidation of Complex Ni-Cu Sulphide Ores and its Implication for Flotation Practice

Abstract

Oxidation of complex nickel-copper sulphides is a serious concern in their flotation. This paper addresses this issue through a study of batch tests using stockpile samples and fresh samples oxidized in the lab. Both the stockpile and the lab samples produced significantly inferior nickel grade recovery compared to the fresh sample due to a significant dilution effect by excessive flotation of pyrrhotite and non-floatability of some pentlandite. Application of a high pH of 10 slowed down pyrrhotite flotation kinetics, but was not able to prevent its excessive recovery. In contrast to behaviour of nickel, chalcopyrite did not show a significant deterioration in its performance due to a relative lack of mineralogical association with pyrrhotite and also a strong floatability regardless of oxidation. Oxidation conditions which induce excessive floatability on pyrrhotite while causing incremental loss in pentlandite floatability appear to be the root cause of difficulties in the processing of these ores.

Oxidation of complex nickel-copper sulphides is a serious concern in their flotation. This paper addresses this issue through a study of batch tests using stockpile samples and fresh samples oxidized in the lab. Both the stockpile and the lab samples produced significantly inferior nickel grade recovery compared to the fresh sample due to a significant dilution effect by excessive flotation of pyrrhotite and non-floatability of some pentlandite. Application of a high pH of 10 slowed down pyrrhotite flotation kinetics, but was not able to prevent its excessive recovery. In contrast to behaviour of nickel, chalcopyrite did not show a significant deterioration in its performance due to a relative lack of mineralogical association with pyrrhotite and also a strong floatability regardless of oxidation. Oxidation conditions which induce excessive floatability on pyrrhotite while causing incremental loss in pentlandite floatability appear to be the root cause of difficulties in the processing of these ores.

L'oxydation des sulfures complexes de nickel-cuivre est d'un intérêt important pour leur flottation. Cet article se concentre sur cette question au moyen d'une étude d'essais en lot en utilisant des échantillons de stockage de réserve et des échantillons frais oxidés en laboratoire. Tant les échantillons de stockage que ceux du laboratoire ont produit une récupération du nickel de qualité significativement inférieure en comparaison avec l'échantillon frais à cause de l'effet important de la dilution due à la flottation excessive de la pyrrhotine et à cause de la non-flottabilité d'une partie de la pentlandite. L'application d'un pH élevé de 10 a ralenti la cinétique de flottation de la pyrrhotine, mais n'a pas été capable d'empêcher sa récupération excessive. En contraste avec le comportement du nickel, la chalcopyrite n'a pas montré de détérioration importante de son rendement à cause d'un manque relatif d'association minéralogique avec la pyrrhotine et aussi à cause d'une forte flottabilité, peu importe l'oxydation. Les conditions d'oxydation qui induisent la flottabilité excessive de la pyrrhotine tout en causant une perte graduelle de la flottabilité de la pentlandite semblent être à l'origine des difficultés de traitement de ces minerais.