Enhanced Surface Charge of Polyamide Thin Film Nanocomposite Membrane

Modified zeolite nanoparticles created from sol-gel process are applied to the synthesis of thin film polyamide nanocomposite membrane for seawater desalination. In this study, iron hydroxide was used for the modification of zeolite nanoparticles to improve their surface charge. During the interfacial polymerization, the iron hydroxide coated zeolite (IZ) nanoparticles were added into the amide monomer solution and the IZ/polyamide nanocomposite layer were formed on the porous polysulfone support. These IZ/polyamide composite membranes had more negatively charged surface compared to pristine zeolite/polyamide and polyamide membranes. The characterization of membranes and nanoparticles were performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). On the desalination test, the resulting IZ/polyamide nanocomposite membranes exhibited improved water permeability with no considerable salt rejection loss. This enhanced desalination performance can be explained by the molecular sieving of zeolite and Donnan-exclusion effect of negatively charged surface.