Study on polyamide thin-film composite nanofiltration membrane by interfacial polymerization of polyvinylamine (PVAm) and isophthaloyl chloride (IPC)

A novel thin-film composite polyamide nanofiltration membrane was prepared through interfacial polymerization of polymeric polyamine polyvinylamine (PVAm) with isophthaloyl chloride (IPC) on a polysulfone supporting film. The composite membranes were prepared under different conditions and characterized in terms of chemical and morphological structures, surface zeta potential, pure water permeability, and rejection to different solutes including electrolytes and sucrose. The results showed that the membrane performance was significantly affected by the content of amine units of PVAm and the concentrations of PVAm and IPC. The increase of the content of amine units of PVAm and the concentration of IPC resulted in an augment in salt rejection and a decrease in permeability, while the increase of PVAm concentration led to enhancement in both the salt rejection and water flux. The obtained membranes were positively charged at pHs lower than 6.5 and negatively charged at pHs higher than 7.0. The rejection order of the membrane changed from MgCl2 > MgSO4 > NaCl > Na2SO4 at pH 3.0 to MgSO4 > Na2SO4 > MgCl2 > NaCl at pH 7.5. The decrease of feed pH from 7.5 to 3.0 resulted in an over 35.0% augment in permeability. Furthermore, the novel nanofiltration membrane is of good performance stability and particularly suitable for treating acidic feed.