Thin porous metal sheet-supported NaA zeolite membrane for water/ethanol separation

This paper reports the preparation and separation testing of a NaA (or 4A-type) water-selective zeolite membrane, which is supported on a robust, porous metal sheet 50 μm thick. This thin sheet support has great potential for the development of a low-cost, inorganic membrane module of high membrane surface area packing density (m2/m3). The porous Ni alloy sheet of micrometer or sub-micrometer mean pore size was prepared in-house to evaluate different zeolite membrane deposition methods and conditions. The membranes were characterized by SEM, XRD and water/ethanol separation tests. High quality NaA zeolite membranes of thickness <2 μm were obtained by the secondary hydrothermal growth method. These membranes show a water/ethanol separation factor of >10,000 and water permeation flux of about 4 kg/(m2 h) at 75 °C with a feed of 10% (w/w) water in ethanol. Stability of the membranes has also been demonstrated in 66-h continuous testing at 75 °C and 90 °C. The separation performance is discussed with different model equations.