It was found that polydispersed hematite particles with a size distribution ranging from 0.1 to 0.6 mum dispersed in water could be efficiently removed from water or divided into two size classes depending on the pH by passing them through a column bed of glass bead. Complete solid/liquid separation of hematite particles was observed in the pH range between 3 to 7, where hematite particle are positively charged, while glass beads are negative. In the pH range from approximately 7.5 to 10, the smaller particles were adsorbed onto the glass beads, while the remaining larger ones passed through the glass bead column bed as an effluent. The size classification was most efficient at pH 8. In the pH range above 11, adhesion of hematite to glass beads was not observed. A tenfold increase in flow rate had virtually no influence on the results. The experimental results were explained in terms of the DLVO theory, with a sphere-plate model.