Selective Flocculation Study of Hematite in HematiteQuartz-Kaolinite System in Presence of Ca2+, Mg2+ and Fe3+ Ions. Part1: Optimization of Ligand

Abstract

Separation of ultrafine hematite from quartz and kaolinite gangue minerals using selective flocculation technique is markedly affected by the state of inter mineral interaction which is governed by type and content of polyvalent metal ions. Because of the presence of polyvalent metal ions hetracoagulation of gangue minerals is widely acknowledged, thus selective flocculation of ultrafine hematite from associated gangue minerals is challenging task when their concentration is above 10 ppm. This study has shown that state of strong interaction of gangue minerals with hematite due to presence of 15 ppm Ca²⁺, 3 ppm Mg²⁺ and 3 ppm Fe³⁺ ions can be weakened by addition of optimal dose of Sodium Hexametaphosphate (SHMP) ligand. The optimization of ligand dose is achieved through analysis of Zeta Potential (ZP) as a function of slurry pH. It is noted that 50 ppm of SHMP is sufficient to restore the ZP of hematite, where selective dispersion of the slurry constituents are possible. Our results further showed that conventional strategy of obtaining minimum difference of ±30 mV in the ZP of hematite and gangue minerals quartz and kaolinite would not work especially in the presence of 15 ppm Ca²⁺, 3 ppm Mg²⁺ and 3 ppm Fe³⁺ ions. Attempts to achieve the minimum threshold difference in the ZP of the minerals will cause over dispersion.