The reverse osmosis membrane technology plays an important role in the supply of pure water. The high water production is always desirable. In this study, a new acid acceptor consisting of the crown ether (18-crown-6)/KOH is used to catalyze the interfacial polymerization reaction for the polyamide reverse osmosis membrane fabrication to increase the membrane flux. The 18- crown-6 and the KOH will form a complex compound, to help the diffusion of the KOH from the aqueous phase to the organic phase, so that the KOH can work more efficiently to catalyze the polymerization. Meanwhile, the 18-crown-6 can effectively inhibit the excess hydrolysis of the TMC from the KOH, preventing a significant deterioration in the ion rejection of the membrane. To verify the above reasoning, the SEM and XPS characterizations are used to show that the membrane has a thin and properly hydrolyzed surface morphology. The membrane performance test shows that the application of the (18-crown-6)/KOH as the acid acceptor can promote the membrane flux better (up to 72% increase) as compared with using only the KOH (38% increase). Moreover, the use of the (18- crown-6)/KOH can help the membrane to maintain a reasonable NaCl rejection of above 90%. That solves the problem of rejection deterioration when only the KOH is used as the acid acceptor with a rejection of below 60%. Although Cs⁺ has a smaller hydraulic radius than that of Na⁺, this kind of membrane also enjoys a similarly excellent separation behavior with respect to CsNO3. That means that the (18-crown-6)/KOH catalyst composition is effective and applicable in future.

reverse osmosis  /  polyamide  /  composite membrane  /  interfacial polymerization  /  acid acceptor  /  crown ether