Blocking defects of zeolite membranes with WS2 nanosheets for vapor permeation dehydration of low water content isopropanol

Abstract

It is difficult for zeolite membrane to behave good separation selectivity in dehydration of low water content isopropanol (IPA) by vapor permeation (VP) because capillary condensation in small intercrystalline defects is usually insufficient for excluding IPA molecules and adsorbate-induced contraction of zeolite crystals open new defects at low water content. To address this issue, a facile and high-efficiency modification strategy was proposed to block defects of NaA zeolite membranes on hollow fibers by using WS2 nanosheets. Effect of nanosheets thickness on VP separation performance of modified membranes was investigated. It showed that the separation factor of membrane was improved by more than two orders of magnitude (from 60 to >10000) after modified with the few-layer WS2 nanosheets while the loss in water flux was only 18.6% in VP dehydration of 10 wt% water/IPA mixture at 373 K. Moreover, the modified membrane still maintained a high separation factor of ~5000 rather than that of pristine membrane (336) even when the feed water content lowered to 0.5 wt%, indicating that not only intrinsic defects but also the crystal contraction-induced defects were blocked simultaneously by the thin WS2 nanosheets.