A facile preparation of high flux NaA zeolite membranes by direct secondary growth of wet gel layer

NaA zeolite membranes were first applied in industrial organic solvent dehydration in 1999. However, issues such as poor reproducibility, low flux, and high cost of NaA zeolite membrane preparation have hindered its industrial progress. In this work, a direct secondary growth of wet gel layer method is employed. Specifically, a wet gel layer is coated to the outer surface of the seeded support, which is then placed into the Teflon-lined autoclave without additional hydrogel inside. Under the conditions of conventional secondary growth (100 °C for 4 h), high flux NaA zeolite membranes can be prepared. The pervaporation performance in the 90 wt% ethanol/water solution is tested at 75 °C, showing the flux up to 4.59 kg m−2 h−1 and the separation factor above 10,000. The controlling factors involved in the preparation of high flux NaA zeolite membranes using the direct secondary growth of wet gel layer are investigated. It is found that the introduction method of the seed layer and wet gel layer, the size of the seed, the state of the gel, and the immersion time play significant roles in the formation of zeolite membranes with superior separation performance. This method provides a new idea for the preparation of high performance, low cost and reproducible zeolite membranes with prospects for industrial application.