Flotation of sphalerite and pyrite in the presence of sodium sulfite

Sodium sulfite was used to improve the separation of copper-activated sphal erite from pyrite in mildly alkaline pH conditions. This improved separatio n was mainly the result of the much larger depression of the flotation of p yrite than sphalerite. A further improvement in this separation was obtaine d by conditioning the minerals with oxygen and by decreasing the time inter val between sulfite and xanthate additions. The results of spectroscopic st udies have shown that sodium sulfite promotes the oxidation of copper on py rite as copper hydroxide, but has no effect on sphalerite. This increase in the amount of oxidation products on the pyrite surface and, as a result, d ecrease in xanthate adsorption may explain the depression of the flotation of pyrite in the presence of sodium sulfite. (C) 2001 Elsevier Science B.V. All rights reserved.