Enhancing Permeability of Thin Film Nanocomposite Membranes via Covalent Linking of Polyamide with the Incorporated Metal–Organic Frameworks

Thin film nanocomposite (TFN) membranes were invented in 2007 to enhance the permeability of thin film composite (TFC) membranes. Surface modification of nanofillers was a common method to improve the interaction and compatibility at polymer/nanofiller interfaces. Accordingly, as an amino-functionalized zirconium-based metal–organic framework (MOF), UiO-66-NH2 was synthesized and introduced into the preparation of TFN membranes via interfacial polymerization in this study. The superhydrophilic characteristic of UiO-66-NH2 made it possible to be well dispersed in aqueous solution and the amino groups on particle surfaces could react with 1,3,5-benzenetricarboxylic acid chloride (TMC) to form covalent interaction with polymer thus inhibiting the formation of nonselective defects at PA/nanofiller interfaces. The morphology images and FT-IR spectra revealed the PA selective layer successfully formed on the top of hydrolyzed polyacrylonitrile (HPAN) supports. The EDX characterization demonstrated UiO-66-NH2 nanoparticles were successfully introduced into the TFN membranes. The UiO-66-NH2 nanoparticles increased the surface hydrophilicity and roughness of the membranes, and provided additional passageways for mass transfer. Pure water permeability increased from 6.89 LMH/bar for TFC membrane to 14.55 LMH/bar for TFN-0.10 membrane indicating the distinct permeability elevation after the incorporation of UiO-66-NH2 nanoparticles. And the Na2SO4 rejection of TFN-0.10 membrane was up to about 99.0% and NaCl rejection was 38.1% at 4 bar, which was higher than that of TFN membrane incorporated with pristine UiO-66.