Selective flocculation of ultrafine hematite with sodium polyacrylate

The separation of ultrafine hematite and kaolinite using classical flotation and magnetic separation techniques is challenging due to their very fine particle size, which easily contaminates the concentrate, resulting in low grades. This research examines the flocculation effects and mechanisms of sodium polyacrylate (PAAS) on hematite and kaolinite through flocculation experiments, particle size analysis, zeta potential measurements, FTIR, and XPS analysis. The flocculation tests indicated that with a PAAS dosage of 2.25 mg·L-1, ultrafine hematite exhibited good flocculation, with the average particle size increasing from 2.59 μm to 42.88 μm, and the fractal dimension could reach 1.59. Changes in zeta potential and adsorption amount showed that at a PAAS dosage of 2.25 mg·L-1, the zeta potential reached a peak of -3.53 mV, and the adsorption amount was 0.01 mg/g. The adsorption isotherm fitting results suggested that PAAS adsorption on hematite and kaolinite follows the Langmuir equation more closely, with hematite demonstrating better PAAS adsorption properties. FTIR analysis showed that sodium polyacrylate was chemisorbed on the surface of hematite. It was determined by XPS analysis that Fe3+ on the hematite surface reacted with the reactive group -COO - in sodium polyacrylate.