X-ray photoelectron spectroscopic study of montmorillonite containing exchangeable divalent cations

Abstract

Montmorillonite containing divalent Mg, Ca, Sr, Ba or Cd as an exchangeable cation has been studied by X-ray photoelectron spectroscopy and X-ray-induced Auger electron spectroscopy. The relative atomic abundances of the exchangeable cations in the montmorillonite samples, obtained by X.p.s. measurements, are consistent with the cation-exchange capacity of the montmorillonite. A comparison of the photoelectron binding energies and Auger electron kinetic energies of the exchangeable cations with those of corresponding halides and oxides reveals that they fall among those of corresponding cations in typical ionic compounds such as fluorides and chlorides. On the other hand, the bonding state of the non-exchangeable Mg ion in montmorillonite lattice, as indicated by the Mg ls and KL_{2, 3}L_{2, 3} Auger electron energies, is similar to that of magnesium oxide and distinguishable from that of the exchangeable Mg ion.