Preparation method of polyamide nanofiltration membrane with polyaldehyde cross-linked polyvinyl alcohol as middle layer

The invention discloses a preparation method of a polyamide nanofiltration membrane with polyaldehyde cross-linked polyvinyl alcohol as a middle layer, relates to a preparation method of a nanofiltration membrane, and aims to solve the technical problems that the membrane surface of the conventional nanofiltration membrane with a sandwich structure is easy to pollute, the membrane is easy to expand and the stability is poor. The method comprises the following steps: 1, preparing a polyaldehyde cross-linked polyvinyl alcohol middle layer membrane on the surface of a polyethersulfone microfiltration membrane; 2, absorbing a multi-amino or multi-imino substance by a middle layer film; and 3, reacting the multi-amino or multi-imino substance on the middle layer membrane with the multi-acyl chloride substance to obtain the polyamide nanofiltration membrane with the multi-aldehyde cross-linked polyvinyl alcohol as the middle layer. The retention rate of the nanofiltration membrane is 90%-98%, and the membrane flux