▎ 摘　　要

NOVELTY - Preparation of multi-separation layer composite nanofiltration membrane involves: (1) fixing a base membrane facing upward in a membrane tank of a dynamic layer-by-layer self-assembling system; (2) preparing membrane covered with a single-layer cationic polyelectrolyte; (3) preparing a membrane covered with a graphene oxide (GO)-cationic polyelectrolyte double layer; (4) repeating the steps (2,3), so that the polyelectrolyte and GO solutions are alternately and dynamically self-assembled layer by layer on the membrane surface to obtain multilayer GO-polyelectrolyte composite membrane; (5) contacting the surface of the membrane with m-phenylenediamine aqueous phase solution, draining liquid on the membrane surface, contacting with trimesoyl chloride organic phase solution, and draining liquid to obtain multilayer GO-polyelectrolyte and polyamide composite film; and (6) heat-treating the membrane and washing. USE - Preparation of multi-separation layer composite nanofiltration membrane used for drinking water treatment, wastewater treatment, seawater softening, and separation and purification. ADVANTAGE - The method organically combines the interfacial polymerization method and the dynamic layer-by-layer self-assembly method, and solves the problems of low flux, anti-pollution performance and low membrane-making efficiency of the polyamide nanofiltration membrane, strengthens the performance of nanofiltration membrane, and uses graphene oxide, which has excellent hydrophilicity and stable chemical properties. The membrane surface is rich in hydrophilic functional groups and has nano-sized pores. DETAILED DESCRIPTION - Preparation of multi-separation layer composite nanofiltration membrane involves: (1) fixing a base membrane facing upward in a membrane tank of a dynamic layer-by-layer self-assembling system; (2) making a cationic polyelectrolyte solution transversely flow through the base membrane surface under pressure condition for dynamic layer-by-layer self-assembly using the system, switching the raw liquid into deionized water, and washing the membrane surface to obtain a membrane covered with a single-layer cationic polyelectrolyte; (3) making a graphene oxide (GO) solution transversely flow through the base membrane surface single-layer cationic polyelectrolyte under the pressure condition for dynamic layer-by-layer self-assembly, switching the raw liquid into deionized water, and washing the membrane surface to obtain a membrane covered with a GO-cationic polyelectrolyte double layer; (4) repeating the steps (2) and (3) 2-4 times and 1-3 times, respectively of the membrane covered with GO-cationic polyelectrolyte double-layer, so that the cationic polyelectrolyte solution and GO solution are alternately and dynamically self-assembled layer by layer on the membrane surface to obtain membrane covered with 2.5-4.5 GO-cationic polyelectrolyte double-layer, and recording as multilayer GO-polyelectrolyte composite membrane; (5) contacting the surface of the membrane with m-phenylenediamine aqueous phase solution, draining the liquid on the membrane surface, contacting with trimesoyl chloride organic phase solution, and draining the liquid on the membrane surface to obtain multilayer GO-polyelectrolyte and polyamide composite film; and (6) heat-treating the membrane and water washing.