Location of Li(I), Cu(II) and Cd(II) in heated montmorillonite: evidence from specular reflectance infrared and electron spin resonance spectroscopies

Abstract

Specular reflectance infrared and electron spin resonance spectroscopies were employed for the analysis of the sites of Li(i), Cu(II) and Cd(II) cations fixed in the structure of montmorillonite from Jelšový Potok (Slovakia) upon heating for 24 h at 300 °C. Li(i) cations are trapped in two different sites: in the previously vacant octahedra and in the hexagonal holes of the tetrahedral sheet. Cu(II) cations are fixed deep in the hexagonal holes. They substantially affect the vibration modes of Si-O bonds and they can be partially coordinated by oxygen atoms from the mineral layers and by nitrogen atoms from pyridine molecules, if present in the interlayers. The larger Cd(II) cations do not get so deep into the hexagonal holes as the Cu(II) ions and their effect on Si-O bonds is less pronounced.