Method for modifying surface of polyamide composite film

The invention discloses a method for modifying the surface of a polyamide composite film. The method comprises steps as follows: (1), copolymers containing nitrogen heterocylic groups such as imidazole, pyridine and the like are dissolved in a solvent, and a coating solution is prepared; (2), the to-be-modified polyamide composite film is soaked in the coating solution for a certain period of time and then is taken out and dried, and a coating is formed on the surface of the film; (3), the polyamide composite film with the surface coated with the coating is subjected to surface quaternization crosslinking treatment, a nitrogen heterocylic zwitterionic polymer gel layer is formed on the surface of the film. The anti-pollution capacity and the anti-chlorine performance of the surface modified polyamide composite film are remarkably improved, and the service life of the polyamide composite film in applications of nanofiltration separation, reverse osmosis seawater desalination and the like is prolonged. The process is simple, the reaction condition is mild, and the method plays an important role in improvement of comprehensive performance of the polyamide composite film.