Surface Modification to Fabricate Superhydrophobic and Superoleophilic Alumina Membranes for Oil/Water Separation

A facile approach for fabrication of superhydrophobic and superoleophilic alumina membranes through surface modification is presented in this work. The modified alumina membranes were prepared through thermal decomposition of polytetrafluoroethylene (PTFE) materials on the surface of alumina membranes. Contact angle (CA) measurement shows that the modified alumina membranes exhibit superhydrophobicity (155°) and superoleophilicity (0°). Results of Fourier transform infrared spectroscopy, X-ray energy dispersive spectrometry, and X-ray photoelectron spectroscopy indicate that the fluoric groups were formed on the surface of the modified alumina membranes, which may be due to partial decomposition of the PTFE polymer and deposition during the sintering process. This is the key to hydrophobicity. Field emission scanning electron microscopy images demonstrate the occurrence of the fluoric layer, which further indicated that the pore size of the modified alumina membranes decreased. After sintering at 400 °C over 7 h under a nitrogen atmosphere, values of water rejection of the modified alumina membranes for oil/water separation are all higher than 97% over 4 h. A slight reduction in permeation flux can be found over 48 h. The results indicate the fluoric layer is firmly linked with the alumina membranes. The as-prepared membranes may have great potential for oil/water separation.