Ionothermal Synthesis of CHA-Type Zeolite Membrane for Desalination

Zeolite chabazite (CHA) membranes with a higher Si/Al mole ratio in the zeolite framework were prepared to improve their stability and separation performance. Pure zeolite CHA membranes were synthesized with imidazolium-based ionic liquids (ILs) as a structure-directing agent, which could improve the Si/Al ratio in the framework. ILs could be used repetitively at least 3 times for the synthesis of high-crystallinity zeolites. Under the optimized synthetic conditions, a continued zeolite CHA membrane obtained from an initial gel containing 1-buthyl-3-methylimidazolium bromide ([Bmim]Br) on the mullite tubular supports has a high water flux of 6.3 kg/(m²·h) with a high ion rejection (100%) for pervaporation (PV) separation of 3.5% (in mass fraction) NaCl aqueous solution at 75 ℃ . The effects of temperature and feed concentration on the desalination performance of ILs-CHA membranes were also investigated. The water flux increases to 10.3 kg/(m²·h), and their salt rejections are 100% when the operating PV temperature increases at 90 ℃ . Zeolite CHA membranes prepared have the superior separation performance even for desalination of 10% NaCl aqueous solution. Furthermore, the ILs-CHA zeolite membrane has a stable separation performance with a stable water flux as well as a high salt rejection in 3.5% NaCl aqueous solution at 75 ℃ for 3.5 d.