Structural parameters reduction in polyamide forward osmosis membranes via click modification of the polysulfone support

Abstract

To reduce the structural parameter of composite polyamide (PA) forward osmosis membrane, the support polysulfone (PSf) was prepared by blending PSf/PSf-g-methoxypolyethylene glycol (PSf/PSf-g-mPEG) with the mPEG weight molecular weights of 200, 500, 1000 and 1900 g/mol at the PSf/PSf-g-mPEG weight ratios of 4:1 and 9:1, respectively. The composite membranes were prepared as the following steps: (1) propargyl mPEGs preparation; (2) chloromethylation and azidation of PSf; (3) PSf-g-mPEG preparation via click chemistry; (4) PSf/PSf-g-mPEG blended support membrane preparation by phase separation; (5) polyamide active layer formation through interfacial polymerization between phenylenediamine and 1,3,5-benzenetricarbonyl trichloride on the support membrane.The successful synthesis of the polymers and preparation of the composite membranes were certified with Fourier transform infrared spectroscopy, nuclear magnetic resonance, X-ray photoelectron spectroscopy analysis, field emission scanning electron microscope and energy dispersive spectrometer.The pure water fluxes of the blended support membranes were sharply increased; the maximum pure water flux was gained for the PSf/PSf-g-mPEG500 blended membrane. For the composite polyamide (PA) membrane, the water flux was improved drastically, while the rejection to the salt remained unchanged in the reverse osmosis system; the pure water flux rose dramatically and the structure parameter (S) dropped significantly in the forward osmosis system.