Influences of the zeolite loading and particle size in composite hollow fiber supports on properties of zeolite NaA membranes

NaA/polymer composite hollow fibers (CHF) used as zeolite NaA membrane supports are fabricated from the dope slurry of NaA zeolite, N-methyl-2-pyrrolidone (NMP) and polyethersulfone (PES) using a dry–wet spinning process. The CHF supports can avoid seeding process and have great potential for developing low-cost zeolite membranes with high reproducibility. The influences of the spinning condition, the zeolite loading and particle size on the properties of the CHF supports and zeolite NaA membranes are investigated in detail. The supports and membranes were characterized by SEM, bending strength tests and water/ethanol pervaporation separation tests. Dense membranes with the separation factor >10,000 were obtained on the Z1 (4.0 μm)-85 (85 wt.% NaA) and Z2 (1.5 μm)-75 supports after the synthesis of 5 h, while the zeolite membranes obtained on the Z1-70 and Z1-75 supports had pinholes. A dense membrane with the separation factor >10,000 was obtained on the Z2-85 support after the synthesis of 4 h. The results indicate that the CHF supports with smaller zeolite particles were better as the supports for zeolite NaA membranes. The flux of the zeolite membrane on the CHF support increased with the zeolite loading because the increase of the zeolite loading resulted in the increase of the support porosity. However, the increase of the zeolite loading can reduce the mechanical strength of the supports.

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► Effects of spinning conditions on properties of CHF supports are studied.
► The higher is the zeolite loading, the quicker the growth of the zeolite membrane.
► The flux of the membrane increases with the porosity of the CHF support.
► Small zeolite crystals in CHF can improve the growth of the zeolite membrane.