Preparation of High-Performance Porous Zeolite-Silica Membranes for Water Desalination

Membrane-based technologies for water purification and desalination have been increasingly applied to address the global challenges of water scarcity and the pollution of aquatic environments1. However, the polymer membranes used in water desalination often have problems such as fouling, scaling, and short service life2-3. In contrast, inorganic membranes are made up of ceramics or metals and possess good mechanical, structural and thermal strength. Therefore, it is of great significance to study new inorganic alternative membranes for water desalination. Among them, the inorganic zeolites have been widely used in separation, due to their high stability and defined pore structure4. Therefore, this project focuses on the development of high-performance water desalination membranes through a combination of crystals zeolites and amorphous sol-gel derived silica. Specifically, a well-selected ZSM-5 zeolite-amorphous silica thin layer (<1µm) is deposited on a porous alumina substrate. The boundaries defect could be eliminated by combining the amorphous silica with the zeolite crystals. The ZSM-5 possess nanopores with optimized pore size and pore structure for achieving optimum permeability and selectivity concerning water desalination. We use the sol-gel method to deposit amorphous silica thin films, embedding the ZSM-5 particles in it. The templates N,N-Dimethylformamide（DMF）is added to silica during the sol-gel process in order to control the pore structure to optimize water permeability and salt rejection. The amorphous silica is doped with ZrO2 to increase the membrane performances and stability during desalination process. Finally, the membrane thickness is minimized to less than 1µm while avoiding the formation of defects, thus allowing for high water permeation rates while rejecting salts. This research provides a new way to make a high-performance membrane for water desalination through a combination of amorphous-crystalline materials.
Key words: Inorganic membranes; Zeolite; ZSM-5; Amorphous Silica; Desalination; Sol-gel