Selective seeding for magnetic Separation

Selective seeding utilizes surface chemistry to bond a desired mineral or minerals to introduced ferromagnetic seeds. Experiments were performed using finely ground Al(OH)3(gibbsite), SiO2(quartz), and Fe3O4(magnetite). The mineral particles were screened and only those having grain sizes between 20 and 2 μm were used. The materials were dispersed in a water slurry with 5% solid contents by 100 ppm Na2S and/or 100 ppm NaF. Two ppm polyacrylamide-acrylate was employed to flocculate Al(OH)3and Fe3O4. Magnetic separation in a HGMS coarse stainless steel wool model filter removed 73% of the SiO2and the Al(OH)3was upgraded from 40% to 69% with 93% yield. Repeated dispersal both chemically and mechanically with subsequent flocculation resulted in further upgrading of Al(OH)3to 79% with 87% recovery after the 3rd stage. Magnetite was finally recovered at 92% purity with 83% yield.