Polyamide thin-film composite membrane based on nano-silica modified polysulfone microporous support layer for forward osmosis

In this study, polyamide thin-film nanocomposite (TFN) membranes were prepared on nanosilica-modified polysulfone (PSf) support layers for forward osmosis (FO) applications. Different contents of SiO2 nanoparticles (1, 3, and 5 wt%) were added to a dope solution to develop FO membranes with improved performance. The effects of SiO2 on the membranes were investigated by attenuated total reflectance-Fourier transform infrared spectrometry, scanning electron microscope, hydrophilicity measurement, and mechanical property tests. The results showed that the wettability of PSf substrates was improved with increasing concentrations of SiO2. The resulting TFN membranes had smaller structural parameters, which meant lower internal concentration polarization effects compared to typical thin-film composite membranes. However, SiO2 nanoparticle is a good modifying agent to enhance water permeability, but it could not improve the selectivity of TFN membranes. The FO performance was evaluated using deionized water as feed solution and either 1 or 2 M NaCl as draw solution in both membrane orientations. The FO water flux of the fabricated membranes increased from 9.1 to 22.3 LMH when the active layer faced the feed solution (AL-FS) and 18.2 to 41.9 LMH when the active layer was placed towards the draw solution (AL-DS), mainly due to the improvement of PSf substrate with an addition of SiO2.