Novel Insight on the Effect of the Monomer Concentration on the Polypiperazine-Amide Nanofiltration Membrane

Abstract

The monomer concentration is a key factor affecting the diffusion rate and reaction rate of the monomers and determines the physicochemical property of polyamide nanofiltration membranes. However, the mechanism of the monomer concentration effect on the polyamide nanofiltration membrane remains unclear. The properties of nascent membranes fabricated with different monomer concentrations with a fixed ratio presented completely new results in the absence of heat treatment. The results reveal that the polyamide layer thickness increases linearly with the monomer concentration when the concentration is high. The nanofiltration membranes prepared at a low concentration have a larger pore size and a lower cross-linking degree, which contributed to high water permeability. The optimal membrane presented a high pure water permeability of 36.1 L h–1 m–2 bar–1, with the Na2SO4 rejection maintained at 98.4%. This work provides a novel insight into the relationship between the properties of the nanofiltration membrane and monomer concentration.