Highly chlorine resistant polyamide reverse osmosis membranes realized by interfacial polymerization at a free interface with a buffer layer

The polyamide (PA) reverse osmosis (RO) membranes prepared by interfacial polymerization at a free aqueous–organic interface always suffer from polymerization instability on the free-interface and low chlorine resistance. Focusing on these problems, in this study, a new approach was proposed which introduced an additional buffer layer to assist the free-interfacial polymerization (BLFIP). And due to the adjustment of the mitigation of the organic phase and water phase on the free-interface, defect-free PA membranes with significantly improved surface smoothness were successfully prepared by the proposed BLFIP process and the resultant membranes demonstrated superior desalination performance compared to the PA membranes prepared with the previous technique. With the optimized concentration of 0.3 wt.% trimesoyl chloride (TMC) and 0.6 wt.%, m-xylylenediamine, the prepared BLFIP PA membrane showed salt rejection rate of 92.55%, 92.01%, 83.99% and 95.16%, to Na 2 SO 4 , MgSO 4 , NaCl and methyl orange, respectively at 5 bar, while maintained a water flux of about 2 Lm –2 h –1 bar –1 . More importantly, the BLFIP PA membrane possesses excellent long-term stability, and chlorine resistance comparing with traditional PA membranes based on TMC and m-phenylenediamine, which demonstrated the new method in this study paved a facile way for preparing RO filtration membranes with outstanding performance in seawater desalination.