FAR-IR SPECTROSCOPIC STUDIES ON ZEOLITE NACAA

The location of sodium and calcium cations in zeolite A has been studi ed using far-IR spectroscopy. Spectroscopic measurements show a shift in the vibrational spectra with the partial replacement of Na+ by Ca2 cations in the zeolite matrix. The magnitude of these shifts is obser ved to be dependent upon the location of the exchanged cations in the matrix; the effect being more prominent in the region 170-230 cm-1. Th e zeolite having highest calcium content shows a new band at around 23 1 cm-1. Our studies show that for up to 76% calcium exchange of the ze olite, the calcium cations are located only at site A. When calcium ex change is 95%, these cations are located at sites B and C with no cati on observed at site A. The unusual adsorption behavior of high calcium zeolite A has been ascribed to the calcium cations located at site B.