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[Display omitted] • Ultra-thin CHA and FAU membranes were evaluated for desalination by pervaporation. • The observed water flux was 24 kg/(m2‧h) for CHA and 28 kg/(m2‧h) for FAU membranes. • The effect of the support was estimated using a mathematical model. • The water flux could be much higher without the effect of the support. In the present work, ultra-thin zeolite CHA and FAU membranes, with thicknesses of 600 and 500 nm, respectively, were evaluated for desalination by pervaporation at various temperatures. Single gas permeation experiments were employed to verify high quality of the membranes. At 90 °C, the observed water fluxes for CHA and FAU membranes were as high as 24 and 28 kg/(m2‧h), respectively. A mathematical model was used to estimate the effect of the support. The results showed that the mass transfer resistance of the support reduced the flux. The water flux corrected for the mass transfer resistance over the support was as high as 40 and 51 kg/(m2‧h) at 90 °C for CHA and FAU membranes, respectively. To the best of our knowledge, these are the highest reported water fluxes for desalination by zeolite membranes in a pervaporation process. [ABSTRACT FROM AUTHOR]

Ultra-thin MFI membranes (0.5 μm) were evaluated for recovery of alcohols from dilute aqueous mixtures by pervaporation at high temperature and pressure for the first time. The feed pressure was sufficiently high to keep the feed in liquid state at high temperature, while the permeate pressure was kept at atmospheric and a low flow of sweep gas was used to reduce the partial pressure on the permeate side. Atmospheric pressure on the permeate side is more practical than vacuum. High feed temperature and pressure result in high fugacity in the liquid feed, which, in combination with lower permeate pressure, results in a large driving force. Consequently, the membrane exhibited very high fluxes for feeds comprised of 10 wt% ethanol/water and 5 wt% n -butanol/water mixtures at 110 °C and 140 °C, respectively. The flux observed for 10 wt% ethanol/water mixtures was as high as about 52 kg m −2 h −1 , i.e., 6 times higher than the highest previously reported flux for this separation using zeolite membranes in pervaporation. For 5 wt% n -butanol/water mixtures, the flux was 40 kg m −2 h −1 , which is 11 times higher than the highest previously reported flux for this separation by zeolite membranes. At these conditions, the membrane displayed separation factors for ethanol/water and n -butanol/water mixtures of 5 and 16, respectively. However, after about 6 h of operation, the separation factor decreased significantly and the flux increased due to formation of defects in the membrane when the feed was saturated with silica. Lower membrane stability was observed for silica free feeds. The work has shown that it is possible to obtain high flux in pervaporation by using ultra-thin membranes in combination with high feed temperature. The observed membrane selectivity was not excellent, due to pressure drop over the support as well as likely concentration polarisation on the feed side resulting from the high flux. Membrane stability was also an issue at these conditions, however it was shown that stability could be improved by saturating the feed with silica. [ABSTRACT FROM AUTHOR]