Nanofiltration membranes with enhanced performance by constructing an interlayer integrated with dextran nanoparticles and polyethyleneimine coating

Abstract

The thin-film composite (TFC) nanofiltration (NF) membrane is a novel kind of membrane that has been extensively studied in recent years and broadly applied in desalination and wastewater treatment. The improvement of separation performance by optimizing the structure and morphology of NF membranes can significantly reduce energy consumption and bring more economic benefits. In this work, glutaraldehyde (GA) was used to crosslink polyethyleneimine (PEI) and dextran nanoparticles (DNPs) to construct an interfacial coating interlayer on polysulfone (PSF) ultrafiltration (UF) substrate. Subsequently, the polyamide (PA) NF membranes were fabricated by interfacial polymerization (IP) between piperazine (PIP) and trimesoyl chloride (TMC). DNPs were semi-encapsulated in the PEI coating and the exposed nanoparticles would be embedded in the PA layer for forming interfacial channels after IP. The interlayer not only affected the adsorption and diffusion of aqueous phase monomers to form a thin membrane, but also improved the membrane density to prevent selective defects associated with the incorporation of nanoparticles. The pure water permeance of the interlayered-TFC NF membrane was determined as 313.3 Lm⁻²h⁻¹MPa⁻¹, which was approximately four-fold that of the pristine membrane. The retention rate of various divalent salts of the NF membrane also significantly improved, and the retention rate of Na₂SO₄ exceeded 99%. This innovative method of interlayer modification has exhibited great potential in rapid desalination and wastewater recovery, providing new possibilities for the preparation of industrial high-performance NF membranes.