Use of dispersants in flotation of molybdenite in seawater

Coating of valuable mineral particles by hydrophilic slimes is known to depress flotation of such particles. This is referred to as a slime-coating. Such a slime coating takes place in the flotation of molybdenite in seawater when pH of the pulp is raised to depress pyrite and Mg(OH)+ hydroxy-complexes and precipitating magnesium hydroxide accumulate on the molybdenite surface. The dispersant tested in this paper, sodium hexametaphosphate, is shown to be able to restore molybdenite flotation in the pH range in which it is depressed by magnesium species. Addition of hexametaphosphate was found not to affect floatability of pyrite.