Thin-film composite nanofiltration membranes with poly (amidoxime) as organic interlayer for effective desalination

Abstract

Water pollution and scarcity have become a huge challenge to society. Hence, it is urgent to develop nanofiltration (NF) membranes with high permeance and high rejection for efficient desalination and wastewater treatment. Herein, novel NF membranes with poly (amidoxime) (PAO) as organic interlayer were prepared by the method of first coating and then interfacial polymerization (IP). The obtained NF membranes showed the regular nano-strips Turing structure and the polyamide (PA) layer thickness was as thin as 18.2 nm, which was probably attributed that the amidoxime groups significantly enhanced the surface hydrophilicity of poly (ether sulfone) (PES) support, and PAO as organic interlayer can bind with piperazine (PIP) through hydrogen bonding and Lewis acid-base interaction to reduce the diffusion rate of PIP, resulting in the unstable oil-water interface during IP reaction. As a result, the corresponding NF membrane exhibited the permeance up to 25.2 L/m2 h bar with a rejection above 99% for Na2SO4, yielding an overall desalination performance superior to traditional NF membrane and most of NF membranes with inorganic nanomaterials as interlayer. Our work provides a simple avenue to fabricate advanced thin-film composite NF membranes with outstanding separation performance.