Effect of grinding media on the activation of pyrite flotation

Abstract

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,b). In this study, the effect of the grinding conditions on the activation of pyrite by Cu 2+ and Pb 2+ 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 Cu 2+ and Pb 2+ 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 Cu 2+. This is an electrochemical process. However, adsorption of lead hydroxide on pyrite surface is principally responsible for the activation of pyrite flotation by Pb 2+. The effect of grinding media on the flotation of pyrite activated by Cu 2+ or Pb 2+ 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 Cu 2+. 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 Pb 2+. This study provides a clear picture of how to increase or decrease pyrite flotation through a smart selection of grinding media.