The rhodamine B intercalation of montmorillonite

Abstract

Using photometric methods the dissociation constants and weight fractions of rhodamine B dimer in water solutions at different concentrations were determined. The montmorillonite (SWy) samples were fully intercalated with rhodamine B (RhB) solutions at various monomer/dimer ratios. The amount of rhodamine B in fully intercalated montmorillonite (RhB–SWy) increases with increasing concentration of dye in water solutions, i.e., with increasing dimer/monomer ratio. The sum of exchangeable guest cations in RhB–SWy is approximately constant (0.900 meq g−1) for all samples, because RhB–SWy samples with prevailing dye monomer also contain higher amounts of non-exchanged alkali elements. The experimental data are supported by calculated structure models that illustrate the changes in RhB–SWy structure depending on monomeric and/or dimeric arrangement of guests. The analysis of the calculated structure models confirmed the existence of two phases with different basal spacings, d1.8 and 2.3 nm, revealed by X-ray diffraction.