Free-Supported Geopolymer-Based NaA Zeolite Membrane for PGME Dehydration Purification

Self-supported gradient bilayer NaA zeolite membranes were hydrothermally converted from geopolymer precursors for pervaporative dehydration of the propylene glycol methyl ether (PGME)/water azeotrope. XRD confirms crystallization of amorphous geopolymer into NaA zeolite. The 9 mm-thick membrane comprises a thin surface NaA-selective layer and a porous substrate providing low-resistance feed transport. The membrane shows preferential water adsorption and separates via the adsorption–diffusion mechanism. Performance depends on feed temperature and PGME concentration. At 30 °C and 95 wt% PGME, it achieves a flux of 1.1 kg·m−2·h−1 and an ultrahigh separation factor of 2695, far exceeding conventional PVA membranes. This low-cost membrane demonstrates excellent potential for lab-scale organic solvent dehydration.