Role of Dispersants in the Interactions between Clay Minerals and Copper Sulfides in Seawater

摘要

Accumulation of hydrophilic slimes on the surface of valuable minerals, commonly referred to as slime coating, affects flotation of such mineral particles. It was previously reported that the depressing effect of kaolinite on chalcopyrite flotation in seawater is related to the formation of hydrolyzed species of calcium and magnesium which induce heterocoagulation between kaolinite and chalcopyrite. It was also reported that in the molybdenite flotation in seawater, Mg(OH)+ hydroxy-complexes accumulate on the molybdenite surface in the process resembling slime-coating, and that sodium hexametaphospate restores molybdenite flotation in the pH range over which it is depressed by magnesium species. In this study, the interactions between chalcopyrite and kaolinites of different crystallinity, over the pH range from 8 to 11 was studied, when flotation is carried out in seawater, and in a 0.01M NaCl solution. The effect of the dispersants, sodium hexametaphospate and sodium silicate, was evaluated. The results show that the depressing effect of kaolinite on chalcopyrite flotation in seawater correlates very well with the formation of hydrolyzed species of calcium and magnesium. Both dispersants are able to restore chalcopyrite flotation in the presence of kaolinite in seawater over the pH range over which the interactions between both species are enhanced by precipitation of magnesium and calcium hydroxy-complexes. These conclusions were obtained from results using micro-flotation and batch flotation tests with synthetic ores.