Enhancing the Flotation Separation of Copper–Molybdenum Sulfide Minerals by Reducing Molybdenite Agglomeration Through the Use of Dispersants

To address the challenges associated with the agglomeration and encapsulation of chalcopyrite by molybdenite in flotation slurries, which hinder the effective separation of copper and molybdenum, this study investigated the effects of various dispersants on the dispersion behavior of chalcopyrite and molybdenite, along with the underlying mechanisms. Optical microscopy, focused beam reflectance measurements (FBRM), infrared spectroscopy, zeta potential analysis, and other analytical techniques were employed. The results revealed that the dispersion behaviors of chalcopyrite and molybdenite align with the EDLVO theoretical model. At a slurry pH of 12, the dispersant effectively dispersed molybdenite and minimized its agglomeration around chalcopyrite. The dispersive capabilities of the tested dispersants followed the order: sodium carbonate (Na 2 CO 3 ) > sodium hexametaphosphate (SHMP, (NaPO 3 ) 6 ) > sodium silicate (Na 2 O·nSiO 2 ) > ammonium bicarbonate (NH 4 HCO 3 ). Specifically, carbonate ions produced by the hydrolysis of Na2CO3 were chemically adsorbed onto the molybdenite surface, while hexametaphosphate primarily adhered through physical adsorption. This adsorption enhanced the dispersion of molybdenite particles by increasing electrostatic repulsion between them. Mixed ore flotation experiments demonstrated that both Na 2 CO 3 and SHMP significantly reduced the copper grade in the molybdenum concentrate, from 3.95% to 2.69% and 2.67%, respectively.