The selective flotation of pentlandite from a nickel ore

Abstract Nickel sulphide ores containing pentlandite, pyrrhotite and talc have traditionally been treated by bulk sulphide flotation, an approach which seeks to maximise nickel recovery and talc rejection but which does not reject pyrrhotite. Concentrates have therefore been of moderate grade containing as much pyrrhotite as pentlandite or more. In this research a procedure has been devised which rejects much of the pyrrhotite while maintaining the necessary level of talc rejection. In batch tests on an ore containing pentlandite, pyrrhotite, pyrite and talc the procedure rejected 57% of the iron sulphides and 98% of the talc and recovered 81% of the nickel in a concentrate assaying 16.5% Ni. By comparison, a standard bulk float rejected only 6% of the iron sulphides and recovered 80% of the nickel in a concentrate assaying 10.6% Ni. The tendency throughout was for the pyrite to concentrate with the pentlandite. The procedure exploits the particle size dependence of pentlandite and pyrrhotite flotation, the different ways that pH change and each of the reagents copper sulphate, xanthate and guar gum affect the flotability of each of the minerals in the ore and the influence of the grinding medium on iron sulphide flotability. Its main limitation is the poor recovery of fine (−10 μm) pentlandite, a limitation it shares with bulk flotation.