Current
special wetting materials designed for use with oily wastewater
are usually classified as either the oil-removing type or the water-removing
type, which are unifunctional and limited by the oil density. Inspired
by the integrated Janus system of the lotus leaf as well as the mussel-like
mollusks adhered to the lotus, we fabricated a Janus polydopamine
(PDA)–polyethylene terephthalate/polytetrafluoroethylene (PET/PTFE)
membrane by simple immersion and tape-peeling. This membrane shows
a lotuslike Janus wettability, self-cleaning effect, and floating
property. Furthermore, the Janus membrane can separate light oil (ρoil water)/water mixtures with the superhydrophilic
side facing upward, while heavy oil (ρoil > ρwater)/water mixtures are separated with the hydrophobic side
facing upward. The separation efficiency is outstanding even after
10 repeats (>99.10%). By aid of drainage of acetone, the separation
process has avoided the use of external pressure. Moreover, integrated
separations of oil-in-water and water-in-oil emulsions were achieved
with high efficiency. This simply prepared PDA–PET/PTFE Janus
membrane has realized an integrated separation system, overcoming
the monotony of traditional special wettability separation membrane
and extending the bionics field into oily wastewater treatment