Fabrication of hierarchical ZSM-5 zeolite membranes for ultrafiltration

Hierarchical ZSM-5 zeolite membranes were synthesized through secondary growth method in the presence of small amount of cetyltrimethylammonium bromide (CTAB). The results show that CTAB spherical micelles and molecular sieve particles self-assembled to form ordered mesoporous structure. At the same time, the presence of CTAB micelles and hydrophobic long chains suppresses the growth of crystals. By adjusting the CTAB/SiO₂ molar ratio, synthesis temperature or crystallization time, the crystal grain size and the crosslinking degree of the zeolite membranes were changed remarkably to realize the simple and effective regulation of the average pore size, ranging from 7 to 30 nm. Under the synthesis at 180℃ for 20 h and the CTAB/SiO₂ molar ratio about 0.05, the obtained zeolite membrane exhibited a high water permeability of 138 kg·m^-2·h^-1·MPa^-1, and a molecular weight cut-off(MWCO) of 28500, corresponding to the average pore size of 7.39 nm, achieving the standard of small aperture ultrafiltration.