Assembly of polyamide nanofilms for nanofiltration membranes with ultra-high desalination performance.

A method of assembling nanofilms for nanofiltration (NF) composite membranes with ultra-high desalination performance was developed in this work. A series of graphene quantum dots enhanced polyamide (GPA) nanofilms were primarily prepared via support-free interfacial polymerization. Subsequently, the NF composite membranes with two GPA nanofilms (GPA-GPA) layer-by-layer (LBL) assembly were elaborately designed to achieve effective desalination process. The residual amine groups and acyl chloride groups on the surfaces of GPA nanofilms reasonably formed a nascent polyamide (PA) interlayer between two functional layers. The separation performance of GPA-GPA assembly membranes was dramatically developed through the in-situ formed PA interlayer with network pore structure. Most of assembled NF membranes exhibited Na 2 SO 4 rejection rate above 99.5%, and the permeance was above 20.0 L m−2 h−1 bar−1. This creative strategy of in-situ constructing PA interlayer opened up an innovative path for the design of NF membranes with excellent desalination performance. [Display omitted] • Graphene quantum dots enhanced polyamide (GPA) nanofilms were fabricated by support-free interfacial polymerization. • The layer-by-layer assembly of GPA nanofilms was developed to prepare nanofiltration composite membranes. • The residual amine groups and acyl chloride groups of nanofilms formed polyamide interlayer via covalent bonds. • The ultra-high desalination performance was attributed to the in-situ formed network pores of interlayer. [ABSTRACT FROM AUTHOR]