Permeation mechanism of water through microporous SiO_2-ZrO_2 membranes for separation of aqueous solutions of organic solvents by pervaporation

摘要

Pervaporation was conducted with a microporous SiO_2-ZrO_2 membrane at 50 and 75 deg C for separation of aqueous solutions of organic solvents such as acetone, isopropyl alcohol (IPA) and dioxane. The SiO_2-ZrO_2 membrane showed quite high fluxes of around 300 mol/(m~2 h) with large separation factors of 3800 for dioxane/water mixture and of 2800 for IPA/water mixture at 80 mol% of organic solvents at 75 deg C, for example. A simple permeation model, which was proposed previously [Kitao et al, Key Eng. Mater. 61/62 (1991) 175], has been modified with the temperature and concentration polarization in order to understand the water transport characteristics across the membrane in details. Good agreements were obtained between the simulated results and the observed data. The water permeation through the micropores has been found not simply proportional to the partial water vapor pressure of the feed but complicatedly dependent on the capillary suction pressure, the osmotic pressure and on the partial water vapor pressure, as well. The effects of the membrane thickness, pore structures and film resistances at the membrane surface on the water flux are discussed by the model simulations.