A poly(sulfobetaine) hollow fiber ultrafiltration membrane for the treatment of oily wastewater

Abstract

A poly(sulfobetaine) (PSB) hollow fiber ultrafiltration (UF) membrane with permanent hydrophilicity was obtained by forming a thick PSB layer on the surface and subsurface of poly(vinylidene fluoride) (PVDF) hollow fiber microfiltration (MF) membrane. After immersed in 40 mmol/L NaCl solution, the sieving layer (PSB layer) of the UF membrane stretched completely. The PSB hollow fiber UF membrane with sieving layer and MWCO of 5.2 μm and 85–105 kDa, respectively, was formed, which contributed to the great improvement of hydrophilicity, membrane strength, and thermal property. The PSB hollow fiber UF membrane showed a good filtration performance with the permeate flux and oil rejection of ≈300 L/m2 h and >80% at 0.1 MPa, respectively, and an excellent anti-oil-fouling property with the relative flux recovery of >98% during the filtration of the oily water with 40 mmol/L NaCl and at pH 6. More than 90% of oil droplets were rejected by the membrane while the soluble oil permeated through the membrane. The fouling mechanisms involved in the MF and UF processes of the oily water were analyzed using Hermia’s models. The results showed that intermediate blocking and cake layer formation or combinations of them were found during the UF experiments for the PSB hollow fiber membrane. By means of the simple immersion, the transformation of surface pores between “opened” and “closed” during the filtration of the oily water can be obtained. The results extended the application of PSB hollow fiber membrane in treatment of oily wastewater and purification of water.