The effect of galvanic interaction on the behaviour of the froth phase during the flotation of a complex sulphide ore
A literature review has shown that the chemical effects of grinding media on the flotation of real ores, especially those containing pyrite, are still not understood adequately. Many studies have been conducted on isolated minerals or in solutions only, and transport phenomena in the froth phase have generally been ignored in studies on galvanic interactions. A complex ore containing galena, sphalerite, chalcopyrite and significant quantities of magnetite, pyrrhotite and pyrite was used in batch flotation tests to study this problem. Metallic iron powder was added in different quantities to a ceramic ball mill in order to simulate the use of mild steel grinding media in flotation tests aimed at selectively floating chalcopyrite. An oxygen-saturated pulp milled in the presence of iron yielded the best recovery of chalcopyrite and copper-lead selectivity. Milling under a nitrogen atmosphere in the absence of metallic iron resulted in poor copper-lead selectivity. The galvanic interaction caused by the presence of iron yielded a stable, well-drained froth with low ratios of solids/water recovery and larger bubbles in the froth. However, milling in the absence of iron caused an extremely brittle froth with very fine bu bubbles, high recoveries of low grades of sulphur. In contrast with the improvement in the copper recovery and copper-lead selectivity obtained when the pulp was pre-aerated after milling in the presence of iron, no significant increase in the copper grade was observed after extensive pre-aeration when milling occurred in the absence of iron. The unsatisfactory flotation results in the absence of iron could be explained by the enhanced floatability of iron-bearing gangue minerals, which rupture films and suppress froth stability owing to bubble-overloading. © 1993.