Ricerc@Sapienza

In this work, the chemical structural characterization of the erionite-type zeolite from
Agua Prieta, Sonora, México, was performed on both pristine and Na, Ca, and Mg exchanged
samples in order to identify the various modifications due to cation exchange. The samples
investigated were those that showed the best behaviour of CO2 and CH4 adsorption at zero coverage
levels and the higher values of surface area reported in our previous studies. According to the
crystal-chemical formula (Na3.44K1.96Mg0.63Ca0.62)[Al8.21Si27.79O71.85] x 29.63H2O, the pristine sample
has been classified as erionite-Na. Morphological FE-SEM investigation performed on both pristine
(ERIN) and Na-exchanged samples (ERINa3) showed a similar range of fiber diameters (27–37 nm).
The chemical analyses of the ion-exchanged samples evidenced the upload of Ca and Mg following
ion exchange with Na. Rietveld analysis results allowed the identification of the chemical structural
modification caused by the ion exchange process, occurring mainly at the Ca1 site.