Attachment and Detachment of Submicron Particles to and from a Quartz Plate in Aqueous Solutions

Abstract

The attachment of submicron particles of iron (III) oxide and silver iodide to a quartz plate and their detachment from it through the force of gravity in aqueous solutions were investigated using a rectangular quartz cell. The zeta potentials of the particles and plate were determined by electrophoresis and electro-osmosis, respectively. The particle attachment and detachment phenomena were analyzed on the basis of the heterocoagulation theory. The magnitude of the energy barrier to prevent particle attachment was estimated to be 150200kT for both kinds of submicron particles. The energy barrier to detachment was calculated assuming the separation distance to be Å. The magnitude of the energy barrier was reasonable for detachment efficiency in the absence or presence of concentrations of sodium dodecyl sulfate, SDS, less than 1×10^-3M. At concentrations higher than 2×10^-3M, the separation distance increased to about 10Å by the penetrating effects of SDS. A kinetic analysis of the detachment process for iron (III) oxide particles indicated particle detachment to occur as rapid and slow processes, and the rate constant of the latter not depending on SDS concentrations but that of the former, ks to increase with SDS concentration. For iron (III) oxide particles dried and aged in air, the values of ks decreased with increasing aging time.