The effect of electrolytes on the flotation of pyrite

Abstract

In the flotation of pyrite a minimum concentration of any ions is necessary to stabilize the froth and thus produce a reasonable recovery of pyrite. In the absence of ions a "dry froth" is formed which results in a decreased mass pull and thus a low pyrite recovery. The predominant effect of an .increased concentration of univalent ions was a decrease in ·the formation of "dry froth" during flotation which resulted in an increase in pyrite recovery. This was due to the increase in froth stability with the addition of ions and was verified in the two and three phase froth stability tests. The predominant effects of the divalent ions were: (i) an increase in froth stability resulting in increased pyrite recovery (ii) a sharp increase in grade due to a decrease in gangue recovery (iii) a decreased rate of flotation. The decrease in gangue recovery was possibly due to the effect of the ion on the compression of the electrical double layer resulting in coagulation of the quartz particles. The slow rate of flotation was ascribed to the slow rate of the ascent of the heavily mineralized bubbles. This increase in bubble mineralization could be due to coagulation of pyrite in the pulp phase. The adsorption of the collector, sodium ethyl xanthate, on pyrite was not affected by the univalent or divalent cations but decreased with the addition of the nitrate anion. However these variations in xanthate adsorption did not seem to have a significant effect on the flotation of pyrite. Flotation experiments using oxidised ore showed a reduced pyrite recovery compared with the leached ore. This was ascribed to the low xanthate adsorption and the low natural floatability of the ore.