Separation of aluminosilicates and diaspore from diasporic-bauxite by selective flocculation

Abstract

The flocculation tests of four pure minerals (diaspore, kaolinite, illite, pyrophyllite) and bauxite ore were investigated by the sedimentation. The dispersion behavior of the four pure minerals shows a very good consistency with the variation of zeta potential. The concentrate with the mass ratio of Al₂O₃ to SiO₂ (m(Al₂O₃)/m(SiO₂)) 8.90 and the recovery of Al₂O₃ 86.98% is obtained from bauxite ore (m(Al₂O₃)/m(SiO₂)=5.68) in pH range of 9.5–10.0 by using sodium carbonate (5 kg/t) and sodium polyacrylate (7 g/t) as dispersant and flocculant respectively. Sodium carbonate acts as both pH modifier and favorable dispersant for aluminosilicates. The high performance of sodium polyacrylate on flocculation for diaspore is contributed to the carboxyl of sodium polyacrylate that interacts with active Al sites on diaspore by chemical absorption, and the hydrogen bond effects between hydroxyl group of macromolecule and surface Al-OH on diaspore to accelerate the sedimentation of diaspore.

Keywords

diasporic-bauxite / sodium carbonate / sodium polyacrylate / ratio of Al₂O₃ to SiO₂ / selective flocculation / flocculant / dispersant