Ion-Specific Interaction of Alumina Surfaces

Abstract

There has been a long-standing question about the effect of the type of ionic species on the surface forces that is not considered in the classical Derjaguin-Landau-Vervey-Overbeek theory. Originating from the work of Hofmeister, the ion-specific interaction between particles has been known for a long time. Depending on the pH and oxide type, a direct or a reverse Hofmeister effect has been observed in colloidal suspensions at high salt concentrations. The origin of this effect is not well understood but is qualitatively taken into account in colloid science. From macroscopic behavior, it is predicted that alumina particles in LiCl solution attract each other more strongly than in CsCl solutions. If such an effect does exist, then force curves obtained using the colloid probe technique may detect the difference. Using chloride salts of the two end members of the Hofmeister series, namely Li+ and Cs+, stronger attraction in the LiCl electrolyte solution compared with the CsCl one was measured for the first time at the microlevel between alumina surfaces at pH=11.