A spiral-windable, free-standing, durable membrane constructed with ultralong hydrogel@MnO₂ nanowires for oil/water separation under harsh environment

An ideal membrane for oil/water separation at industrial scale is expected to possess the combined merits of excellent separation performance, sound mechanical flexibility, and high durability under harsh environments. In response to these challenging requirements, we came up with a new concept to design the membrane constructed with ultralong hydrogel-functionalized MnO₂ nanowires. The super-oleophobic nanowires form highly open and tight pore structures within the membrane, which endows its high permeation flux (2800 L h⁻¹ m⁻² bar⁻¹), high oil/water separation efficiency (>99 %) and low fouling tendency for separating emulsified oil from water. Furthermore, the brittleness problem of MnO₂ materials is collectively resolved due to the high aspect ratio and surface functionalization of the hydrogel-functionalized MnO₂ nanowires. This results in the new membrane with extraordinary mechanical flexibility and potential for spiral-wound membrane modules, which are highly desired in industrial applications due to a lower footprint and lower capital cost. The new membrane also demonstrates high durability under harsh environments with non-neutral pH values or high salinities. Given its facile synthesis process and inexpensive materials, this spiral-windable and durable membrane with high separation performance has the great potential to be applied at industrial scale for oily wastewater treatment under harsh environments.