SPECIFIC SURFACE AREA BY CO-ION EXCLUSION MEASUREMENTS: INFLUENCE OF EXPERIMENTAL CONDITIONS
A. Nennemann1, L. Ammann1, O. Mecking1 , T. Permien2, G. Lagaly1
1 Institute of Inorganic Chemistry, University Kiel, D-24098 Kiel,
für Bau, Landesentwicklung und Umwelt Mecklenburg-Vorpommern, Schloßstr. 6-8,
D-19053 Schwerin, Germany
The high specific surface area is an important characteristic of bentonites, kaolins and clays. Organic and inorganic pollutant adsorption e. g. in soils and clay barriers strongly depends on the specific surface area of the material. The main component of a bentonite is montmorillonite. Montmorillonite particles in a dispersion at low electrolyte concentrations delaminate into sheets or tactoids. The specific surface area depends on the degree of delamination.
The three important methods to determine the specific surface area of montmorillonites are gas adsorption, organic cation adsorption and co-ion exclusion measurements. Only the latter two methods allow estimating the surface area in a dispersion. The aim of this work was to study the experimental conditions of co-ion exclusion measurements. Experiments with raw and purified bentonites were performed.