Fabrication of stainless steel hollow fiber supported NaA zeolite membrane by self-assembly of submicron seeds

Submicron NaA zeolite seeds were coated on the stainless steel (SS) hollow fiber support by self-assembly method, and then the hydrothermal crystallization and autoclave technique were used to synthesize NaA zeolite membranes. The effects of grafting temperature, grafting time and the size of induction seeds on the membrane performance were extensively investigated. The as-synthesized membranes and zeolite crystals were then characterized by X-ray diffraction, and the morphology and thickness of membranes were examined by scanning electron microscopy. The separation performance of the membrane was evaluated by pervaporation dehydration of 90 wt% ethanol/water mixtures at 75 °C. It was found that the seed-layer should be uniformly coated to induce good continuity for the NaA zeolite membrane layer, where the seeding effect was clearly affected by grafting time, grafting temperature and seed size. The optimal seeding condition was found for a grafting time of 6 h under a temperature of 110 °C, using a seed size of 150 nm. A continuous zeolite membrane layer could be obtained on the surface of the SS hollow fiber, with a separation factor above 10,000 and a permeation flux of 4.22 kg∙m⁻²∙h⁻¹. The proposed self-assembly method could be readily operated and extended to the seeding process during the preparation of other supported zeolite membranes, providing a good prospect in batch-scale production of SS hollow fiber supported NaA zeolite membranes.