The depression of pyrite (FeS2) through an organic depressant is not only ineffective but also nonselective which causes poor selectivity. In this research, the depression effect of an organic polymer ‘poly-γ-glutamic acid (γ-PGA, a widely available class of polysaccharides)’ on pyrite flotation was improved by the addition of lime (CaO). The most encouraging flotation results were received at relatively lower concentrations of CaO and γ-PGA. The addition of CaO and γ-PGA had a synergistic inhibitory effect on pyrite flotation with a minor compromise in terms of the chalcopyrite grade at low alkaline conditions (pH 9). Adsorption studies and zeta potential measurements revealed that both CaO and γ-PGA were greatly adsorbed onto the pyrite surface than chalcopyrite. The addition of CaO and γ-PGA underwent a two-step depression effect on pyrite surface: (1) calcium species dissolved from CaO prefrentially adsorbed onto the pyrite surface and decreasing its negative charges; (2) pre-adsorbed calcium hydroxyl species promoted the adsorption of γ-PGA onto the pyrite surface. The XPS and FT-IR measurements revealed that γ-PGA formed the chemical coordination bonds with Caspecies on pyrite surface. Based on these measurement analyses, a two-step depression mechanism of CaO and γ-PGA on pyrite was also proposed. The envisaged scheme has its own benefits of environmental friendliness and cost-effective characteristics in Cu\\S flotation systems.
Synergistic depression phenomenon