Efficient construction of a robust PTFE/Al₂O₃ hydrophobic membrane for effective oil purification

Membrane separation has been proven to be a promising technology for waste-oil purification. However, the efficient preparation of hydrophobic and strong membrane materials has always been one of the bottlenecks and the object of research focus in the field. Here, we developed an efficient construction method for preparing a hydrophobic membrane with a robust polytetrafluoroethylene (PTFE) top layer. The macroporous ceramic substrate was applied instead of the ceramic membrane as the support of the PTFE layer. Meanwhile, two-dimensional graphene oxide was introduced to partially pre-fill the large pores on the surface of the substrate. Resultantly, the binding depth between the membrane layer and the substrate was properly tailored. The excessive infiltration of the PTFE membrane layer was avoided, and there was a strong binding between the membrane layer and the ceramic substrate. The effects of the graphene oxide and PTFE loadings and thermal treatment on the microstructure and performance of the composite membrane were systematically studied. The optimized PTFE/alumina composite membrane exhibited a water contact angle of ∼ 135°, an average pore size of ∼ 200 nm, and a layer thickness of 6.5 μm. Additionally, the prepared composite membrane exhibited excellent separation performance for emulsified water and particle suspensions in oil.