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Résumé :
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In previous study, it has been found that the grinding conditions have a great effect on the flotation of chalcopyrite and galena as well as their separation from pyrite ( [Peng et al., 2003a] and [Peng et al., 2003b]). In this study, the effect of the grinding conditions on the activation of pyrite by Cu2+ and Pb2+ were investigated. Based on flotation behaviour, EDTA (ethylene diamine-tetra acid) extraction, pulp potential measurement and electrokinetic study, it is found that the activation of pyrite flotation by Cu2+ and Pb2+ involves different mechanisms. Reduction of copper(II) to copper(I) and the formation of new copper sulphide phases are responsible for the activation of pyrite flotation by Cu2+. This is an electrochemical process. However, adsorption of lead hydroxide on pyrite surface is principally responsible for the activation of pyrite flotation by Pb2+. The effect of grinding media on the flotation of pyrite activated by Cu2+ or Pb2+ is through the change of pulp potential and iron oxidation species emanating from the media. The iron oxidation species from grinding media is electrostatically repulsive with respect to copper-activated pyrite and therefore, reducing conditions produced by mild steel medium promotes pyrite flotation in the presence of Cu2+. However, iron oxidation species from grinding media is electrostatically attractive with respect to lead-activated pyrite and therefore inert grinding medium favours pyrite flotation in the presence of Pb2+. This study provides a clear picture of how to increase or decrease pyrite flotation through a smart selection of grinding media.
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