Yin-Yang membrane with dual superwettabilities for controllable separation of complex oil/water mixtures

Oil spill incidents and massive discharge of oily industrial wastewater have a profound negative impact on the global water ecosystem. Super-wettable membranes have emerged as a promising solution for oil/water separation. However, challenges arise when this technique is applied to different kinds of oily wastewater, especially triphase heavy oil/light oil/water mixtures, because of the membranes' single function and limited applicability. Drawing inspiration from the Taiji diagram, we proposed a novel 'Yin-Yang' membrane (YYM) with dual superwettabilities to address these challenges. The unique dual superwettabilities make it possible to precisely independently adjust the wetting film and the corresponding liquid permeability at the Yin and Yang regions through the controllable pre-wetting. The YYM could achieve continuous separation with a high efficiency (over 99.1 %) and a large total flux (over 50.5 × 103 L·m−2·h−1) for triphase oil/water mixtures, regardless of liquid species and densities. Proof-of-concept experiments highlight the noticeable biocompatibility of YYM-filtrated water from hypertoxic oily wastewater. The YYMs enlighten the design of new super-wettable materials for use in hazardous waste elimination and water ecological restoration.