Synthesis of thin film nanocomposite forward osmosis membrane with enhancement in water flux without sacrificing salt rejection

• Synthesis of novel TFN FO membrane using PSf–TiO2 nanocomposite substrate
• The resulting TFN FO membrane exhibited small S value and minimum ICP.
• Better performance of TFN membrane compared to typical TFC and commercial membranes

In this study, thin film nanocomposite (TFN) membrane was developed using novel polysulfone–titanium dioxide (PSf–TiO2) nanocomposite substrate. The effects of TiO2 on the PSf substrate morphologies, hydrophilicity and water permeability were investigated and discussed. The results revealed that the hydrophilicity and the porosity of the substrate were improved upon the TiO2 addition, leading to significant enhancement in water flux. TFN membrane was then fabricated by establishing a polyamide layer made of 1,3-phenylendiamine and 1,3,5-benzenetricarbonyl trichloride monomers over the surface of the modified substrate. Compared with the typical TFC and commercial CTA membranes, the TFN membrane prepared always demonstrated much higher FO water flux without showing a significant increase in reverse solute flux when tested under same conditions. When tested in AL–FS orientation using 0.5 M NaCl as a draw solution and 10 mM NaCl as feed solution, the water flux of the TFN membrane was ∼ 120% and ∼ 87% higher than that of the commercial membrane and typical TFC membrane, respectively. The water flux of the TFN membrane was also reported to be much higher under prolonged filtration time, mainly due to the improved properties of substrate upon addition of TiO2.

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