Preparation of high performance polyamide membrane by surface modification method for desalination

This work provides a new and simple method to improve the performance of polyamide reverse osmosis membrane, including selectivity properties and antifouling ability. Herein, quaternary ammonium groups have been immobilized on polyamide membrane surface by grafting and self-polymerization reaction of epoxy group in 2,3-epoxypropyl trimethyl ammonium chloride with tris(dimethylaminomethyl) phenol as curing catalyst. The surface properties of the modified membrane, such as surface charge, hydrophilicity and roughness have been characterized in detail and compared with virgin PA membrane. This novel modification method mainly achieves three advances in terms of membrane performance and fabricating technique. On one hand, the positively charged quaternary ammonium group immobilized on membrane surface can prevent cationic surfactant absorbing to improve fouling-resistance, due to the electric repulsion effect. On the other hand, self-poly-merization reaction based on epoxy group occurred on polyamide surface can fill up the aggregate pore or reduce the pore size in polyamide, resulting in the increase of salt rejection. More importantly, the membrane modification process is very simple and efficient, which adapts to fabricate RO membrane with high performance on industrial production line completely.