Enhancing antifouling property of reverse osmosis membranes via surface tethered with the aminated cation of ionic liquids

Abstract

The electrical neutrality of ionic liquids (ILs) was exploited to enhance the antifouling property of polyamide (PA) reverse osmosis (RO) membranes in this work. We solely tethered the aminated imidazolium cation of ILs [AVIM] Br onto the top-surface of PA RO membranes via mild amidation. The molecular simulation results confirmed that the tethered imidazolium cation and the dissociated bromine anion were stably existed in the form of ion pairs on PA RO membrane surface. In virtue of the electrical neutrality of these ion pairs, the ionic-solvation induced hydration layer formed in ILs above the modified membrane surface was thick and evenly distributed, similar to that formed in conventionally electroneutral zwitterion antifouling materials. Thereby, the cation-tethered membrane surface intuitively achieved balanced charge and strong hydrophilicity, and stably exhibited low protein adsorption and excellent antifouling behaviors to diverse foulants, even when the imidazolium cation was paired with anions of different molecular size. Meanwhile, the typical ridge-and-valley surface morphology for PA RO membrane was well preserved due to the mild modification condition, and thereby harvested satisfactory separation performance. The integration of high performance, abundant ILs and mild conditions was expected to expand the application of superb antifouling materials in a variety of biofouling areas.