Recovery of iron values from iron ore slimes by selective magnetic coating

Effective separation of iron values from iron ore slimes using a wet magnetic separator and selective magnetic coating is reported. The selectivity of coating for enhancing the magnetic response of iron particles was achieved by controlling the surface properties of the particles, i.e., electrokinetics potential, through pH adjustment and use of sodium hexa-metaphosphates as the dispersant. Experiments were conducted with synthetic mixtures of iron, alumina, and silica using oleate colloidal magnetite at different fields of magnetic intensity. After the iron values were separated from the synthetic mixtures, the technique was applied to iron ore slimes of Joda area of India. Iron concentrate containing similar to 65.9% Fe, 1.0% SiO2, and 1.56% Al2O3 was obtained from a feed containing -59.0% Fe, 3.98% SiO2, and 6.5% Al2O3. The effects of pH, magnetic intensity, and addition of sodium oleate were recorded. The X-ray diffraction (XRD) studies brought out the significant enrichment of iron in the concentrate relative to the feed, and alumina-silica enhancement in the tailing products. The scanning electron microscopy (SEM) study highlighted the coagulation of hematite and magnetite in the presence of sodium oleate, thereby facilitating the effective separation.