Fig. 5 Model for oleic acid permeates horizontally on the water wetted MIL-100(Fe)
Furthermore, the wettability of used MIL-100(Fe) was studied. With pressing continuously, the water drop was deformative and rolled on the plane of used MIL-100(Fe) (Fig. 6a~e ). Additionally, the static water contact angle (WCA) of used MIL-100(Fe) was up to 179° (Fig. 6f ). Those characteristics of used MIL-100(Fe) suggested that the wettability of used MIL-100(Fe) has changed from amphipathicity to hydrophobicity, and the force of adhere for water on the used MIL-100(Fe) was extremely weak. The hydrophobicity was disadvantage for the contact between the used MIL-100(Fe) and emulsion drops. Therefore, the demulsification performance of used MIL-100(Fe) decreased dramatically (Fig. 3d ).