Experimental studies in magnetic separation of ultrafine hematite

Magnetic filtration of submicron hematite particles passed in aqueous solution through a ball matrix filter has been investigated under conditions of constant flow rate (3 cm/min) and controlled solution pH. The particulates were spherical, with nominal diameters of 0.06 and 0.12 microns. Filtering efficiency in larger fields was better for the smaller particulates, but in fields below several hundred Oe this trend reversed. A reduction from pH=11 to pH=10 resulted in a 10% decrease in removal of 0.06-micron particulates at high fields, and a commensurate increase in low fields