EFFECTS OF SURFACTANTS ON PARTICLE ADHESION .1. INTERACTIONS OF MONODISPERSED COLLOIDAL HEMATITE PARTICLES WITH GLASS-BEADS IN THE PRESENCEOF SODIUM 4-OCTYLBENZENESULFONATE

The kinetics of deposition of colloidal hematite particles on glass be ads in the presence of sodium 4-octylbenzenesulfonate (NaOBS) at const ant pH and ionic strength were studied using the packed column techniq ue. At low concentrations, the surfactant had little effect on the adh esion phenomena, as compared with the same system in its absence. At s ufficiently high concentrations, NaOBS caused charge reversal of hemat ite particles to negative and a restabilization of the suspension, pre venting their deposition under such conditions. It was also establishe d that the adsorption of the surfactant molecules onto particle surfac e was very fast; thus, no equilibration between NaOBS and hematite was necessary in the adhesion studies. At intermediate surfactant content s, either mono- or multi-layer attachment of hematite on glass took pl ace. The kinetics of particle release from monolayer and multiple laye rs by rinsing the loaded column with 10(-2) mol dm(-3) NaOH solutions was also investigated, and the corresponding removal rate constants we re estimated. It was shown that the detachment from multilayers was a slower process than the removal from monolayers. (C) 1997 Published by Elsevier Science B.V.