TiO₂-decorated NaA zeolite membranes with improved separation stability for pervaporation dehydration of N, N-Dimethylacetamide

It is a great challenge for conventional NaA zeolite membrane to maintain stable water flux in pervaporation (PV) dehydration of polar aprotic solvents because the aggressive adsorption of these solvents on membrane surface restrain water adsorption and thereby reduce water flux gradually. To address this issue, a facile surface modification method was adopted to decorate the surface of NaA zeolite membrane with sol-gel derived TiO₂ nanoparticles for PV dehydration of N, N-Dimethylacetamide (DMAc). Effect of TiO₂ precursor composition on properties and separation performance of TiO₂/NaA zeolite composite membranes was investigated extensively in terms of SEM, XRD, XPS, solvent adsorption and water contact angle. The results showed that the porous TiO₂ layer on top of zeolite membrane not only hindered the electrostatic interaction between DMAc molecules and sodium cations from zeolite membrane but also allowed water permeation without large loss in flux. The minimum loss in water flux of TiO₂/NaA zeolite membrane was about 17% after continuous PV dehydration of 10 wt% water/DMAc mixture for 24 h at 363 K while that of bare NaA zeolite membrane was over 95% within 15 h, indicating the effective improvement on separation stability of NaA zeolite membrane for PV dehydration of DMAc.