1-methylimidazole as a novel additive for reverse osmosis membrane with high flux-rejection combinations and good stability

A novel aqueous solution additive, 1-methylimidazole (1-MI), was applied to prepare aromatic polyamide (PA) reverse osmosis (RO) membranes with excellent performance by interfacial polymerization of trimesoyl chloride (TMC) and m-phenylenediamine. The RO membrane structure and performance were characterized in detail. The results indicated that the addition of 1-MI was beneficial to forming the membrane with a dense and thin PA layer. This is because 1-MI could react with TMC, which is in favor of the formation of back surface structure with more pores. The product generated by 1-MI and TMC was hydrolyzed easily, and then endowed the membrane with more carboxylic acid groups. The membrane desalination performance for feeds with different NaCl concentration was evaluated. The membrane prepared with 1-MI possessed a higher flux and rejection because of the thinner and denser PA layer and more carboxylic acid groups. Considering that the membranes inevitably face chemical cleaning with acid or alkaline solutions in the real processes, the RO membranes were exposed to acidic-alkaline solution, and the results showed that the membrane prepared with 1-MI had good pH stability. This study offers a new route for preparing an excellent-performance RO membrane via using 1-MI as an additive.