Separation of pentlandite from serpentine using the selective magnetic coating-magnetic separation technology

Magnetic coating magnetic separation method was proposed to separate pentlandite from serpentine, which is difficult to separate them using flotation. Results show that under certain physical and chemical conditions of slurry, the pentlandite recovery increases with the amounts of magnetite increasing, while the recovery of serpentine remains at a low level, indicating that their separation could be realized. The separation results of the artificial mixtures show that with addition of 5% magnetite, a concentrate of 19.89% Ni with a recovery of 92.46% and MgO mass content of 4.72% are obtained. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrate that quantities of magnetite particles adhere to the pentlandite surfaces whereas the surface of serpentine is not clearly coated by the magnetite. The Zeta potential analyses and DLVO calculations suggest that with the addition of sodium hexametaphosphate (SHMP), the Zeta potential of serpentine reverses from positive to negative while those of pentlandite and magnetite are not affected significantly. Thus, it made the interaction of magnetite-serpentine become repulsion while that of magnetite-pentlandite remain attraction. Consequently, magnetite particles selectively adhere to the surface of pentlandite and enhance its magnetism, resulting in the magnetic separation of pentlandite from serpentine.