Effect of seed coating layer on the microstructure of NaA zeolite separation layer grown on α-alumina support

NaA zeolite/α-alumina composite membranes were hydrothermally synthesized at 100°C for 24 hr by using nanosize seed of 100 nm in diameter and an α-alumina support of 0.1 μm in pore diameter, and then effect of seed coating layer on the microstructure of NaA zeolite separation layer was systematically investigated. In cases when nanosize seed was coated with a monolayer, increment in seed coverage induced small grained and thick NaA zeolite separation layer. On the other hand, in case when nanosize seed was coated with a multilayer, much small grained and thick separation layer was formed. It was clear that an uniform monolayer seed coating is required to grow hydrothermally a thin and defect-free NaA zeolite separation layer. In the present study, it was clearly announced that seed coating layer is a key factor to determine the microstructure of NaA zeolite layer, secondary grown on a porous support