The influence of amine-functionalized SiO2 nanostructures upon nanofiltration membranes

Abstract The addition of nanostructures to nanofiltration (NF) membranes is a strategy commonly used to improve certain of membranes properties. The functionalization of these nanostructures can be used to modify some of their characteristics. Thus, silica nanostructures (SiO2 NSs) amine-functionalized with (3-aminopropyl)trimethoxysilane (APTMS) (SiO2 NS@1) and with 3-[2-(2-aminoethylamino)ethylamino]-propyltrimethoxysilane (AEAEAPTMS) (SiO2 NS@3) were incorporated into NF membranes. These membranes were prepared with polysulfone (PSU), as a support layer, and a thin film comprised of polydopamine (PDA) and polyethyleneimine (PEI). Four different membrane compositions were prepared: M0 (PSU/PDA/PEI), MS (PSU/PDA/PEI+SiO2 NS), M1 (PSU/PDA/PEI+SiO2 NS@1) and M3 (PSU/PDA/PEI+SiO2 NS@3). Morphology, topography, chemical structure, hydrophilicity, flux and rejection of MgCl2 and NaCl were evaluated. Membrane leaching was performed to investigate the possibility of SiO2 NSs release and the ability to impart toxicity to the liquid medium. There was an improvement in the membranes properties, especially when amine-functionalized materials were incorporated. M1 provided the highest permeate flux and salt rejection values. Leaching assays resulted in low Si release from the membranes and the leachates were not toxic to Daphnia magna. Therefore, the addition of amine-functionalized SiO2 NSs in NF membranes can result in better performance and in this study no toxicity was observed to the organism tested.