Creating nanoporosity in Na, Ca and Mg exchanged erionite zeolite

This paper deals with the emergence of pores in natural erionite zeolite during ion-exchange treatment with aqueous Na+, Mg2+ and Ca2+ solutions of different concentrations. The exchange took place at variable time and temperature of exposure. The effect of this cationic exchange upon the zeolite micropores is analysed by scanning electron microscopy, energy dispersive X-ray spectroscopy and N2 adsorption at 76 K. The characterisation results suggest the presence of Na+ at the pores' mouth that causes an increased adsorption inside nanocavities as well as on the external area of the exchanged zeolites. The generation of pores emerging in erionite zeolites after ion exchange was evaluated through Dubinin-Astakhov and classical Barrett-Joyner-Halenda methods. Depending on the exchanging conditions, Na+ was found to be well distributed and accessible for N2 adsorption. The results indicate that the tested exchange treatments with Na+ favour creation of emerging pores, as an increase of the adsorption capacity occurs.