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

Specular reflectance infrared and electron spin resonance spectroscopies we re employed for the analysis of the sites of Li(I), Cu(II) and Cd(II) catio ns fixed in the structure of montmorillonite from Jelsovy Potok (Slovakia) upon heating for 24 h at 300 degrees C. Li(I) Cations are trapped in two di fferent sites: in the previously vacant octahedra and in the hexagonal hole s of the tetrahedral sheet. Cu(II) cations ate 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 b y nitrogen atoms from pyridine molecules, if present in the interlayers. Th e 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.