Preparation of pH-sensitive Composite Nanofiltration Membrane

Positively charged composite nanofiltration (NF) membranes were prepared through interfacial polymerization of poly[2-(N,N-dimethyl amino)ethyl methacrylate](PDMAEMA) on porous polysulfone (PSF) substrate membranes. The effects of pH on swelling ratio (SR) of the pure crosslinked PDMAEMA membrane and on separation performances of the composite NF membrane were investigated. The results show that the quaternized amino groups produced through interfacial polymerization technique are soluble in both phases, which accelerate the crosslinking reaction as self-catalysts. The swelling/contracting behavior of the pure crosslinked PDMAEMA exhibited a well reversible pH sensitive property. Importantly, the rejection and flux of the composite NF membrane show pH-sensitive behavior in NF process. Furthermore, with the help of a relatively novel method to measure membrane conduction, the true zeta potentials calculated on the basis of the streaming potential measurements proved the pH-sensitive behavior of the NF membrane.