The significance of dosing sequence in the flocculation of hematite

In the selective flocculation of iron ore, a dispersant is added in the grinding circuits, with starch added at a subsequent stage. In this work, the effectiveness of this dosing sequence and its reversed dosing sequence was compared through electrophoretic mobility and colloidal stability studies. It was found that the flocculation of hematite pre-conditioned with starch (>= 4 ppm) is not affected by the subsequently added dispersants, since the zeta potential of hematite protected by starch macromolecules is independent of the subsequently added dispersants. On the contrary, for hematite preconditioned with dispersants, the subsequently added starch causes strong steric stabilization, because of reduced number of adsorption sites for the polymer. (C) 2012 Elsevier Ltd. All rights reserved.