Construction of oil-unidirectional membrane for integrated oil collection with lossless transportation and oil-in-water emulsion purification

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 from 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.