Cu(II) and Ni(II) activation in the flotation of quartz, lizardite and chlorite

Chlorite and lizardite are often the major MgO silicate gangue minerals in nickel ores. Although hydrophilic, they nevertheless report to the concentrate as fine particles by entrainment or as locked in composite particles with sulphide minerals. In this study, we have found that chlorite and lizardite, but also quartz, can be activated with Cu(II) and Ni(II) and floated with xanthate in the pH region 7 to 10. In this pH region, copper and nickel hydroxides are stable species and by adsorbing/precipitating on the mineral surface they promote xanthate adsorption (formation of the hydrophobic xanthate species, copper-xanthate and dixanthogen) and therefore the flotation of these minerals. Copper is a much stronger activator of these minerals than nickel between pH 7 and 10. Therefore, chlorite and lizardite may also report to the concentrate by true flotation in the pH range 7 to 10, especially when copper sulphate is added to activate the slow flotation of pentlandite.