Depression mechanism of ZnSO4 and Na2CO3 on talc flotation

Abstract

The depression mechanism of a combination of ZnSO4 and Na2CO3 on talc during chalcopyrite and molybdenite flotation was investigated in-depth using flotation tests, solution speciation calculations, and various characterization techniques. Flotation tests indicate that the effective depression of talc flotation occurred in the pH range of 7−9. In this pH range, speciation calculations for the mixed solution of ZnSO4 and Na2CO3 showed that the Zn5(OH)6(CO3)2 precipitate was the predominant zinc-bearing species, which was further proven by X-ray diffraction and infrared spectroscopy measurements. Zeta potential measurement highlighted that the Zn5(OH)6(CO3)2 precipitate was positively charged while the talc surface was negatively charged in the pH range where talc depression occurred. X-ray photoelectron spectroscopy and field emission scanning electron microscopy confirmed the presence of the zinc-bearing precipitate on the surface of the talc particles treated by the combination of ZnSO4 and Na2CO3. These findings suggested that heterocoagulation between the formed Zn5(OH)6(CO3)2 and talc occurred mainly due to the electrostatic attraction, thereby leading to the depression of talc flotation.