Novel diamine-modified composite nanofiltration membranes with chlorine resistance using monomers of 1,2,4,5-benzene tetracarbonyl chloride and m-phenylenediamine

Abstract

Novel polyamide thin film composite (TFC) nanofiltration (NF) membranes were prepared on polyetherimide supports by the interfacial polymerization of 1,2,4,5-benzene tetracarbonyl chloride and m-phenylenediamine followed by modification with ethylenediamine (EDA). The TFC NF membranes thus prepared were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR), solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS); these results indicated that by covalent bonding with EDA, the unstable carboxylic groups on the initially generated poly(amic acid) (PAA) TFC membrane surfaces were effectively transformed into polyamide, including the methylene group in the chemical structure chain, for preparing the PAA-cov-EDA NF membranes. At an operating pressure of 1.0 MPa, the PAA-cov-EDA NF membrane exhibits a glucose rejection of 90% at a flux of 25 L m⁻² h⁻¹, and a MgSO₄ rejection of 76% at a flux of 31 L m⁻² h⁻¹, in particular demonstrating its superior chlorine resistance, after being immersed in a 200 ppm NaClO solution for 100 h. Such novel polyamide TFC NF membranes have the advantages of mild preparation conditions and high rejection towards low-molecular-weight organics, thus demonstrating their potential in the pharmaceutical industry.