Surface properties of Indian hematite and bauxite and their coating mechanism with colloidal magnetite

Abstract

The selective coating of colloidal magnetite on hematite and bauxite for enhancing the magnetic separation techniques which depends on surface and chemical phenomena is studied. The mechanism of colloidal magnetite interaction with hematite and bauxite is investigated through electrokinetic and IR studies. The point of zero charge and electrophoretic mobilities of pure hematite, bauxite and colloidal magnetite are determined. The effect of various ions such as PO4-3, SiO3-2, and the surfactant such as sodium oleate on surface properties of hematite and bauxite are examined. IR spectroscopy studies indicate that oleate ions are chemically bonded with hematite while it is only physically adsorbed on the surface of bauxite at certain pH. The zeta-potential also correlates the chemical interaction of oleate on hematite. The separation of quartz from hematite and hematite from bauxite is carried out by applying selective colloidal magnetite coating followed by magnetic separation techniques. Hematite is separated in magnetic fraction for both the cases.