Thermal and spectroscopic studies of zeolites exchanged with heavy metals cations

In the present work we show the results of thermal and FTIR studies of a natural zeolite exchanged with monovalent (Na+, K+ and NH4+) and bivalent (Pb2+, Cd2+ and Zn2+) cations. Thermal analysis data for the zeolite samples were obtained by TG/DTG and DSC, and were employed to evaluate the desorption behaviour of water. The thermal stability of these samples was found to depend on the basic character of the zeolite, depending on the presence of larger or smaller electropositive non-framework cations. In the FTIR spectra the introduction of cations caused changes in the intensity of the pseudo lattice bands. These bands are the results of SiO4 and AlO4 ring vibrations and are located at 615 cm−1. The increase in intensity of these bands can be seen as indicating the presence of cations absorbed by the zeolites.