MAGNETIC SEEDING FLOCCULATION OF WEAKLY MAGNETIC IRON MINERALS

Magnetic seeding flocculation (MSF) has been proven as a successful pretreatment for High Gradient Magnetic Separation (HGMS) of weakly magnetic, finely-sized oxidized iron minerals such as specularite, limonite, and siderite. The utilization of an anionic polymer with an optimal molecular weight and degree of hydrolysis, sodium silicate, and 10-mu-m magnetite serving as flocculant, dispersant, and magnetic seed, respectively, can, for example, produce pure specularite at 73.4% recovery in specularite-quartz systems using two-stage MSF-HGMS. The success of the pretreatment can be attributed to the fact that the isoelectric points of the oxidized iron minerals lie at similar pH's (5.4-6.7), considerably higher than the isoelectric point of silica (2.0). At pH 10.5, the anionic flocculant is selectively adsorbed on the oxidized iron minerals, but electrostatically repulsed from silica.