Fabrication and evaluation of effective zeolite membranes for water desalination

Three dense and crack-free membranes of MFI, LTA and AEI typed zeolites were fabricated respectively on porous stainless-steel nets using the seeded growth method. Experiments in couple with simulations were used to investigate water adsorption behaviors in zeolites. The pervaporation desalination of saltwater was evaluated experimentally on the as-prepared membranes at 1.0 atm feed side pressure. Based on the size-exclusion effect, the three zeolite membranes exhibited excellent ion rejection degrees (>99%). The water permeability was improved with increasing testing temperature without ion rejection sacrifice. Moreover, the reversible water uptakes calculated using adsorption-desorption isotherms played a critical influence on water mobility in the zeolite pores. As a result, higher reversible water uptake contributed to facilitate the transport of water molecules across zeolite membranes, evidenced by the water permeability sequence of AEI > LTA > MFI membranes in saltwater desalination. It is clear that reversible water uptake is an important distinction governing water permeability in the pervaporation desalination process, which will provide guidance to select desalination membrane materials for future research.