Preparation of highly selective reverse osmosis membranes by introducing a nonionic surfactant in the organic phase

The development of highly selective polyamide (PA) membranes is critical for improving the quality and efficiency of the reverse osmosis (RO) process. However, the preparation of highly selective RO membranes exhibits some limitations, such as low efficiency and complex preparation process. Herein, RO membranes with high selectivity were prepared by adding Tween 80, a nonionic surfactant, to an organic phase. The state of Tween 80 in the organic phase and its function in the interfacial polymerization process were thoroughly discussed based on the detailed characterization of the organic phase solution and membrane. Furthermore, the optimization of the Tween 80 concentration, organic phase temperature, organic solvent type, and heat treatment temperature enabled the preparation of a membrane with high rejection (99.61%), high water flux (40.28 L m−2 h−1), and high stability. Compared with the virgin membrane, the selectivity of the optimized membrane increased by 136% and its permeability decreased by only 23%. In summary, the nonionic surfactant Tween 80 reacted with trimesoyl chloride (TMC) in the developed membrane preparation method to produce a new product TW-TMC, exhibiting a dual role of a surfactant and a co-monomer in the interfacial polymerization process, thereby regulating the formation and stacking of PA molecules.