Effects of magnetite on magnetic coating behavior in pentlandite and serpentine system

The effects of magnetite as the magnetic seed on magnetic coating behavior in pentlandite and serpentine system were investigated through magnetic separation tests, X-ray diffraction analysis, zeta potential measurements, and calculations of DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. The results show that, the pentlandite recovery increased with the increment of magnetite while the recovery of serpentine remained low. Results obtained from XRD indicate that magnetite adhered predominately to the surface of pentlandite but only marginally to serpentine. Zeta potential measurements demonstrate that at pH values above 4.0, surfaces of serpentine, magnetite and pentlandite were all negatively charged with the sodium hexametaphosphate (SHMP) addition, and the serpentine with a higher negative potential surface following by magnetite and pentlandite. Thus, the repulsive force between pentlandite and serpentine was stronger, which weakens the hetero-aggregation between them. Calculations of DLVO theory indicate that the interaction energy between magnetite and pentlandite particles was higher than that between magnetite and serpentine. Consequently, it was easier for fine magnetite fractions to adhere to the surface of pentlandite particles and enhances its magnetism to allow for the magnetic separation of pentlandite from serpentine. (C) 2015 Elsevier Ltd. All rights reserved.