Removal of iron (III) oxide particles from a quartz plate by liquid flow

Abstract

The detachment of submicron particles of iron (III) oxide from a quartz plate in aqueous solutions was investigated by using a well-defined flow of electro-osmosis in comparison with the ordinary flow of water without electrokinetic effect. A rectangular quartz cell was used for removal experiments. Zeta potentials of the particles and the plate were determined by electrophoresis and electro-osmosis, respectively. When the iron (III) oxide particles adhering to the quartz plate were removed by the electro-osmotic flow or the ordinary (Poiseuille) flow, the removal efficiency increased with increasing hydrodynamic force. The removal efficiency by electro-osmotic flow was almost the same as that by ordinary flow under the condition of the same magnitude of applied hydrodynamic force. The values of volume flow rate for the removal efficiency of 0.5 for the electro-osmotic flow was extremely small compared with that for the ordinary flow, showing the effectiveness of particle removal by electrokinetic effect of electro-osmosis. The kinetic analysis of the particle removal process showed that it was characterized by two different rate constants, the rate constant of the rapid process and that of the slow process. The rate constant of slow process increased with increasing electro-osmotic velocity. This shows that the electro-osmotic flow acts as a mechanical force to overcome the energy barrier in the removal process. The rate constant increased with increasing surfactant concentration and this trend became more noticeable as electro-osmotic velocity increased. It is concluded from this result that the effect of surfactant on particle removal is enhanced by the mechanical force in removal processes.