Development of a sulfated Y-doped nonstoichiometric zirconia/polysulfone composite membrane for treatment of wastewater containing oil

Polysulfone (PSF) is a kind of popular membrane material for treatment of wastewater containing oil, for it is easily fabricated into ultrafiltration membrane or composite membrane. When treated with wastewater, it has a tendency to be contaminated for its hydrophobicity. In order to enhance the hydrophilic and anti-fouling property of membrane, we added sulfated Y-doped nonstoichiometric zirconia (SO42−/ZrO2–Y2O3; SZY particles) to polysulfone and prepared a novel organic–inorganic composite membrane (SZY/PSF) by a sol–gel process. The optimum preparation conditions of composite membranes were: the ratio of solid (polysulfone and SZY particles), solvent and porogen (polyethylene glycol 400) was 1(g):5(mL):0.8(mL); the mass ratio of SZY particles to polysulfone was 15%; the evaporating time was 10 s and the coagulation bath temperature was 20 °C; intermittent ultrasound was on during the preparation process. Composite membranes were characterized by test of tensile strength, contact angel, porosity and pore diameter and scanning electron microscope (SEM). The results show that composite membrane is difficult to be compacted and approaches twice tensile strength of pure polysulfone membrane; contact angel reduces from 78.1° to 36.6°. SEM micrographs indicate that composite membrane owning the asymmetry structure has two layers of compact layer and porous layer with SZY particles uniformly dispersed in PSF. Wastewater containing oil (80 mg/L) was used to investigate the separation performance of composite membrane. The results reveal that oil retention is 99.16% and oil concentration in the permeation is 0.67 mg/L, which meet the requirement for discharge (<10 mg/L). It can be concluded that the composite membranes developed in the study are reasonably resistant to fouling and hence the developed PSF membranes are considered feasible in treating wastewater containing oil.