Preparation method of polyamide composite nanofiltration membrane

The invention discloses a preparation method of a polyamide composite nanofiltration membrane, which comprises the following steps of partially hydrolyzing a polyacrylonitrile-based membrane under alkaline and heat treatment conditions, and activating the membrane in 1-ethyl-(3-dimethyl amino propyl) carbonyl diimine hydrochloride ethylene dichloride-hydrogen chloride (EDC-HCl) and N-hydroxyl succinimide (NHS); and then sequentially immersing the membrane in water phase monomer piperazine with low concentration and organic phase monomer benzenetricarbonyl trichloride, and the polyamide composite nanofiltration membrane is prepared by interfacial polymerization. The preparation method of the polyamide composite nanofiltration membrane has the advantages that compared with a traditional method, the method utilizes monomer solution with low concentration to perform the interfacial polymerization, high permeation flux can be obtained under ultra-low pressure (0.1MPa), and filter dye solution and saline solution have high separation selectivity.