Oily wastewater and oil
spills not only cause large amounts of resource wastefulness,
but threaten water safety and human health. Besides, for some oily
emulsions, the oil droplets are usually valuable, such as the soybean
oil droplets formed during oil manufacture, and
the oil droplets carrying high valued product from
the extraction process or micro-emulsion reactor. Therefore, the
collection and recovery of oil
from water are particularly important.
However, the recovery of oil droplets form emulsions and collection-lossless
transportation of oil spills are still a big challenge, which cannot be solved
by current oil/water separation methods, including the super-wetting strategy. Herein,
we designed and prepared oil-unidirectional Janus membrane via unilateral
decoration of commercial hydrophobic composite microfiltration membranes. The
obtained Janus membrane is composed of a thin hydrophilic layer and thick
hydrophobic supporting layer, and the asymmetric surface wettability can
realize the unidirectional oil-transport property, viz. oil “diode”. Therefore,
the obtained JMs with oil unidirectional transport property can realize the
efficient collection and recovery of various oils. For example, the JM can
effectively draw the micrometer-sized oil droplets from various oil-in-water
emulsions, and realize the collection-lossless
transportation of the oil spills. Our strategy can firmly stimulate
and accelerate the advances of functional membranes toward the broad
intelligent and sustainable usages.