Heat treatment for improving performance of inner-side zeolite NaA membranes on composite hollow fibers

Zeolite NaA membranes are prepared in the lumen side of zeolite/polymer blend (PES-PI) composite hollow fibers. It is demonstrated for the first time that the post-synthesis heat treatment can be used to improve their separation performances. Effects of the heat treatment temperature and time are investigated. Properties of hollow fibers and zeolite membranes before and after heat treatment are characterized by scanning electron microscopy, mechanical test, mercury intrusion method and pervaporation of 90 wt% ethanol aqueous solution at 75 °C. It is found that the continuous zeolite layers keep their original morphologies without any cracks after heat treatment. On the other hand, the compressive strength and separation performance of inner-side zeolite NaA membranes are significantly improved by post-synthesis heat treatment at 240 °C for 6 h. The flux and separation factor of the heat-treated zeolite membranes can be higher than 11.1 kg m−2 h−1 and up to 10,000, respectively.