The recovery of fine iron minerals from quartz and corundum mixtures using selective magnetic coating

The recovery of hematite fines from quartz and corundum using selective magnetic coating was studied as a function of pH, particle size, magnetic colloidal concentration, magnetic field strength and ratio of hematite:quartz. Synthetic mixtures assaying around 45-72% Fe2O3 was upgraded to 90-92% with recovery level of 90-96%. The optimum separation was observed at pH similar to 7.2, colloidal concentration of 0.25 ml/g of hematite and a magnetic intensity of around 0.78 T. Electrophoretic mobility carried out on hematite, colloidal magnetite and quartz system showed a definite differences in their iso-electric points. The selectivity of coating was obtained by controlling the surface properties of the particle, the Zeta-potential being altered by pH adjustment and addition of sodium oleate. The separation of hematite from corundum was achieved by using a dispersant such as sodium hexa metaphosphate. Microscopic, XRD and FTIR studies strongly suggested the coating of magnetite on hematite surfaces. Experiments were also conducted with hematite, corundum and quartz mixture to simulate the condition of Indian iron ore slimes. The results obtained are discussed in this paper. (C) 1999 Elsevier Science B.V. All rights reserved.