The Exchange of Alkylammonium Ions on Na-Laponite

E. F. Vansant and G. Peeters
Department of Chemistry, University of Antwerp (U.I.A.), Wilrijk, Belgium

Abstract: The exchange of various alkylammonium cations from aqueous solution by sodium laponite has been studied. The affinity of the clay for these organic cations was linearly related to the molecular weight, molecular size or chain length of the alkylammonium ions. The affinity for the clay increases regularly with increasing chain length of the primary amines. A comparison of primary, secondary, and tertiary amines, containing the same alkylgroups shows that the affinity increases in the order R1NH3+ < R2NH2+ < R3NH+. These affinity sequences were attributed to important van der Waals contributions and changes in ion hydration states. The thermodynamic excess function, ΔGmE, was calculated and indicated that with respect to the pure homoionic forms the heterogeneous Na+-alkylammonium surface phases were more stable than they would be if the mixing were ideal.

Key Words: Alkylammonium • Exchange • Equilibrium • Isotherms • Laponite

Clays and Clay Minerals; August 1978 v. 26; no. 4; p. 279-284; DOI: 10.1346/CCMN.1978.0260404
© 1978, The Clay Minerals Society
Clay Minerals Society (www.clays.org)