▎ 摘　　要

NOVELTY - Preparing composite nanofiltration membrane assembled layer-by-layer comprises (i) taking 0.01-5 wt.% piperazine as aqueous phase monomer, .01-5 wt.% graphene quantum dot as aqueous phase additive and 0.01-1 wt.% trimesoyl chloride as oil phase monomer, and normal hexane, normal heptane or isoparaffin as organic solution; (ii) fixing porous supporting body on stainless steel wire net, adding aqueous phase in container, spreading oil phase on aqueous phase, performing interfacial polymerization reaction on oil-water two-phase interface region, generating polyamide film; (iii) lifting porous supporting body pre-placed at bottom of container, transferring polyamide film to porous supporting body, performing heat treatment in oven, preparing composite nano-filtration membrane; and (iv) sequentially placing prepared composite nano-filtration membrane on bottom of container, aqueous phase and oil phase in container, lifting supporting body, assembling polyamide film layer-by-layer. USE - The composite nanofiltration membrane assembled layer-by-layer is useful for waste water zero discharge, printing and dyeing waste water treatment, biological medicine and sea water desalting field. ADVANTAGE - The method: has simple process, stable structure of composite nano-filtration membrane, high desalting and separating performance, high water permeation flux, high sodium sulfate interception rate, high separation performance and high separation factor of chloride ion sulfate ion.