Synthesis of MFI zeolite membranes for water desalination

Zeolite membranes have been extensively researched for many industrial separations via gas permeation and liquid pervaporation processes. General separation mechanisms in zeolite membranes include molecular sieving and competitive adsorption and diffusion. Recently, the possibility of using zeolite membranes to remove ions from aqueous solutions by reverse osmosis (RO) has been explored. RO desalination by zeolite membranes may offer an alternative for some difficult water treatment processes such as concentration of low-level radioactive wastewater and desalination of high-concentration organic water produced in oil and gas operations where conventional technologies, including polymeric RO membranes, are either inapplicable or inefficient. MFI zeolite has an effective intracrystal nanopore diameter of 0.51 nm, which is smaller than the sizes of hydrated ions involved in the current systems. As a result, complete rejection of hydrated ions can occur using MFI zeolite membranes. In this research, mullite-supported MFI zeolite membranes were synthesized via the in situ crystallization method. Hydrothermal treatment was conducted in an autoclave at autogenous pressure. The membranes were made by a single hydrothermal treatment and characterized by X-ray diffraction and scanning electron microscope after calcination.