Control of the intercrystalline pathway of zeolite membranes for water purification

The intercrystalline pathway of MFI zeolite membranes was controlled for development of water purification membranes. The size of intercrystalline pathway was increased from nm order to μm order to obtain both microfiltration and absorbent effects. For the zeolite layer to be used as an absorbent, membrane thickness should be controlled. MFI zeolite membranes were prepared by using a dry gel conversion method on a porous alumina capillary substrate. Dried parent gel was coated on a porous substrate and the dried gel was converted to zeolite under high temperature steam. Membrane thickness can be controlled by changing the amount of dried gel coating on the substrate. Pore size of the intercrystalline pathways of MFI zeolite membranes was controlled by adding poly ethylene glycol (PEG) as a polymeric template. MFI zeolite XRD measurement confirmed that was successfully crystallized on the substrate regardless of the presence of PEG. Pore size the of intercrystalline pathway were measured by coupling a low temperature (350°C) calcination and a nano-permporometer. Without PEG addition the pore size was about 6 nm, and this was increased to more than 16 nm by adding PEG (M. W. 1000, PEG/SiO₂=0.1). This indicates that intercrystalline pathways can be controlled by adding PEG during crystallization procedures of zeolite membranes.