Pervaporative desalination of water using natural zeolite membranes

Several deposits of dense natural clinoptilolite, including one from British Columbia, Canada, have been identified which exhibit both high zeolite content and essentially no macroporosity or intercrystalline voids. Sections of zeolite mineral from the British Columbia deposit were machined into thin membranes and used in the pervaporative desalination of water samples with varying salinity levels, including synthetic seawater. Essentially complete rejection of Mg2+ and Ca2+ (99.99% and 98.52%) and high levels of rejection of Na+ and K+ (over 97.5%) were observed when using a synthetic seawater feed at 75 °C and 1 atm feed-side pressure. Water flux through the natural zeolite membranes was dependent on the ion concentration in the feed, the operating temperature and the feed salinity. At 93 °C, water fluxes of 2.5 kg/m2·h and 0.39 kg/m2·h were obtained for feed concentrations of 100 mg/L Na+ and 5500 mg/L Na+, respectively. The high ion rejection and water flux observed for these rugged and economical natural clinoptilolite membranes indicates their potential utility for desalination applications.

► Pervaporative desalination using a rugged, economical, natural zeolite membrane.
► > 98.5% divalent cation rejection and > 97.5% monovalent cation rejection at 75 °C.
► High flux with efficient ion rejection for synthetic seawater.