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A physico-chemical study of the cationic surfactants adsorption on montmorillonite

The adsorption of cetyltrimethylammonium (CTA) bromide and cetylpyridinium (CP) chloride on Na+-rich montmorillonite (MMT) was studied. An ad hoc isotachophoretic (ITP) method was developed for the simultaneous and rapid determination of the cationic surfactants (CSs) adsorbed. In order to decrease the detection limits, ITP was on-line coupled with capillary zone electrophoresis. Adsorption data were analysed by their fitting with adsorption isotherms. The adsorption of CP is well described by the Langmuir isotherm. It indicates the monolayer arrangement of CP on the MMT surface. In case of the CTA data, the best fitting Langmuir-Freundlich model with the power constant r<1 was found. It can be explained by the CTA interactions because of its intercalation into the MMT interlayer space.

adsorption isotherms; montmorillonite; cetyltrimethylammonium; cetylpyridinium; capillary isotachophoresis


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