Uniformly porous polysulfone ultrafiltration membrane induced by PEG-200 as additive for dye removal

Asymmetric, uniform, and porous polysulfone (PSf) flat-sheet membranes were fabricated via the phase inversion method using dimethylformamide (DMF) as solvent and water as coagulant at room temperature. A PSf ultrafiltration membrane was fabricated in literature primarily using polyethene glycol PEG-400 or even higher molecular weight PEG, however, the low molecular weight PEG-200 is less explored. Thus, the effect of the PEG molecular weight (200–20,000 Da), PEG 200 concentration (0–5 wt%), and PSf concentration (14–24 wt%) in the casting solution on membrane properties are systematically investigated in this paper. Membrane morphology, porosity, bubble point, pure water flux (PWF), moisture content, and contact angle were analyzed. SEM analysis confirmed the formation of uniform nanoporous structures, particularly at 3 wt% PEG-200. The increasing PEG-200 concentration in the PSf membrane casting solution leads to enhanced PWF from 103 to 123 L m⁻² h⁻¹ and increased membrane hydrophobicity, as indicated by a rise in contact angle from 40.58° to 69.63°. Thus, the PSf membrane synthesized using the PEG-200 as a pore former shows the higher water flux compared to membrane prepared using PEG-400 or higher molecular weight PEG. With increasing PSf content (from 14 to 24 wt%) in the casting solution, (a) the solute rejection for PEG-100 K improved significantly, from 40.9 % to 81.5 % and (b) the dye rejection was also improved. These membranes with nanopores will thus be useful for the removal of low molecular weight compounds.