Development of antifouling poly(vinylidene fluoride) ultrafiltration membrane with the addition of polyethylene glycol as additive

Abstract

Poly(vinylidene fluoride) (PVDF) is commonly used to fabricate ultrafiltration (UF) membrane due to its excellent thermal stability and chemical resistance. However, it is hydrophobic and hence has higher fouling tendency due to hydrophobic interaction with foulants. In this study, the antifouling properties of PVDF UF membranes was enhanced through the addition/blending of hydrophilic polyethylene glycol (PEG) of varying molecular weight. The addition of low molecular weight (200 Da, 4000 Da) PEG enhances the membrane’s pure water permeability (from 22.049 L/m2 hr bar to 24.791 L/m2 hr bar) which could be explained by the improved surface wettability. However, the addition of large PEG (35k Da) on other hand reduces the membrane’s pure water permeability (from 20.408 L/m2 hr bar to 9.181 L/m2 hr bar), with increasing rejection on humic acid (82.6 % to 98.5 %). This is due to the formation of a denser membrane with narrower surface pores. The membrane synthesized from 20% (w/v) PVDF with the addition of 4 g PEG 4000 Da showed better antifouling characteristic compared to pure PVDF membrane which could be explained by the enhancement of surface hydrophilicity. Nonetheless, the PVDF/PEG composite UF membrane suffered from rejection loss due to the leaching of PEG molecules from the membrane matrix. Lastly, a regeneration test is performed by flushing the used membrane (after the filtration on humic acid) with distilled water for one-hour duration. SEM images on the membrane surface reveals that the deposited humic acid layer was completely removed and the membrane was successfully recovered to its initial state. The results signified that the addition of PEG could enhances the hydrophilicity of the membrane and hence improving the membrane’s antifouling characteristic.