Activation promoted ionic liquid modification of reverse osmosis membrane towards enhanced permeability for desalination

Abstract

Abstract The ionic liquid (1,3-dimethylimidazolium dimethyl phosphate ([MMIM][DMP])) synthesized by addition reaction was used to modify a commercial reverse osmosis (RO) membrane thorough activation method. The activation promoted modification process was completed within just 6−12 min under optimal condition of the immersion time of 4 min, activation temperature of 110 °C and activation time of 4 min. The variation of surface morphologies and properties of the RO membrane were characterized by SEM, AFM, water contact angle, FTIR, and the RO performance was evaluated by desalination of 1000 mg⋅L−1 NaCl aqueous solution. The results showed that the active layer of the modified RO membrane became thinner, smoother, and more hydrophilic with increasing of activation temperature. The IL modified membrane achieved water flux of 33.7 L m−2 h−1 and rejection of 93.2%, showing 62% higher water flux comparing to the pristine membrane and 2.6% decrease in salt rejection. Moreover, the IL modified membrane showed an enhanced anti-fouling property with 95.5% of normalized water flux recovery. This work provides a facile and efficient way to modify and improve separation performance and anti-fouling property of commercial thin film composite (TFC) RO membranes.