Pressure-assisted polydopamine modification of thin-film composite reverse osmosis membranes for enhanced desalination and antifouling performance

Polydopamine (PDA) has been widely used to modify membrane surface with the aims to tune its hydrophilicity and to mitigate its fouling propensity. However, modifications at ambient pressure only occur on the membrane surface and often result in a drop in water permeance, and sometimes also salt rejection. In this work, a pressure assisted coating method was employed to overcome the aforementioned drawbacks by tuning the inner structure of membranes with the aid of applying a hydraulic pressure during the PDA modification. The coating pressure and duration were varied to investigate their effects on water flux and NaCl rejection as well as surface microstructure. After coating with PDA under 2 bar for 3 h, the water permeance and salt rejection of the resultant membranes were respectively enhanced to 3.31 LMH/bar and 98.95%. Simultaneously, the PDAmodified membranes exhibited excellent antifouling behavior upon the exposure to alginate sodium. Thus, the overall desalination performance of TFC membranes is effectively promoted by the newly developed PDA coating method for water treatment and reuse.