Differential flotation of chalcopyrite, pentlandite and pyrrhotite in Ni-Cu sulphide ores

A new method for the treatment of Ni-Cu sulphides ores from the Sudbury region by differential flotation is presented. The method exploits the ease of chalcopyrite floatability in complete or virtual absence of collector, but in the presence of sulphur dioxide, an effective complexing agent such as diethylenetriamine (DETA) and a frother. The mechanism responsible for the observed selectivity involves control of activating metal ions through chelation. In the presence of DETA, pyrrhotite is deactivated and the problem of its natural reactivation minimized. In the absence of collector, sulphur dioxide depresses not only pyrrhotite but also pentlandite by destroying their sulphur-rich hydrophobic surface layers and forming sulphoxy species. This depressant action, which is greatly enhanced in the presence of DETA, does not affect the recovery of chalcopyrite. It has been postulated that selective floatability of chalcopyrite under such conditions is related to steric factors that prevent DETA from coordinating with matrix copper sites. The copper sites thus continue their electrocatalytic activity in the conversion of sulphide ion to elemental sulphur on chalcopyrite. Formation of a sparingly soluble chelate with mixed ligands involving Ni2+, dithionate (S2O62-) and DETA is also believed to play a role in this mineral separation. The depression of pentlandite that takes place in a virtually collector-free environment is reversible in the presence of a sufficient amount of xanthate, while that of pyrrhotite is not. This allows the subsequent selective flotation of pentlandite from pyrrhotite. Copyright (C) 1996 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd.