Synthesis of zeolite NaA membranes with high performance and high reproducibility on coarse macroporous supports
Abstract Pilot-scale zeolite NaA membranes with high PV performance supported on cheap coarse macroporous supports were prepared by one single secondary growth using varying temperature hot dip-coating seeding method (VTHD). Through the VTHD method, a thin, dense and pinhole-free asymmetric NaA seed layer composed of large and small NaA seeds could be manipulated onto the surface of a coarse macroporous support. The large NaA seeds mainly acted as fillers to reduce the pore sizes of the support while the small NaA seeds acted as nuclei to provide sites for NaA crystal growth. The effects of the seed suspension concentrations, the seed sizes and coating temperature on the morphology of the seed layer and the separation performance of the resulting NaA membranes were investigated. The reproducibility of the VTHD method was as high as 70%. The zeolite NaA membrane prepared by the VTHD method showed a water flux of 2.85 kg m −2  h −1 with a separation factor over 10,000 in dehydrating the 90 wt% ethanol/10 wt% water mixture at 343 K. The use of a cheap macroporous support and the high reproducibility of the VTHD method provide the feasibility for large-scale commercial production of low cost zeolite NaA membranes, promoting the broad application of zeolite NaA membranes.