A study on the pervaporation of water–acetic acid mixtures through ZSM-5 zeolite membranes

A study was carried out on the pervaporation of water from water–acetic acid mixtures through tubular ZSM-5 zeolite membranes. ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube by the seed-assisted crystallization method in the absence of organic templates. It was observed that water preferentially permeated with selectivities higher than the selectivity based on the vapor–liquid equilibrium in the entire range of acetic acid concentration. The separation mechanism of water through ZSM-5 zeolite membranes was discussed and compared with that through mordenite membranes. It was found that the permeability coefficients of both water and acetic acid decreased with increasing temperature, although the pervaporation fluxes of both water and acetic acid increased. As a result, it was concluded that the increase in the pervaporation flux with temperature was due to the increase in the driving force in terms of transmembrane partial vapor pressure difference with temperature. According to the mechanism proposed herein, a study was also directed to modify as-synthesized membranes for the improvement in their pervaporation performance. It was observed that both the water flux and the separation factor were increased through a membrane treated in alkaline solution under appropriate conditions.