Zero-Oil-Fouling Membrane With High Coverage of Grafted Zwitterionic Polymer for Separation of Oil-in-Water Emulsions

Nature-Inspired Superwetting Membranes for Emulsified Oily Water Separation

Nature-inspired superhydrophilic and underwater superoleophobic membranes have garnered significant attention due to their promising potential for separating emulsified oily water and addressing water security issues. The exceptional wettability imparts spontaneous water permeability and oil repellency to membranes, accelerating water filtration, enhancing oil isolation, and reducing membrane fouling during the process, thereby achieving fast and efficient oil-water separation. Over the past decade, a series of groundbreaking studies on nature-inspired superwetting membranes have propelled oily water separation technology into a transformative phase of development. In the subsequent phase, people still face the challenge of evolving superwetting membranes with the dual capabilities of purifying water and recovering oil from particularly surfactant-stabilized emulsions to achieve sustainable resource utilization and zero liquid discharge. In this Perspective, we briefly review recent advances in superwetting membranes, emphasizing their advantages, bionic principles, design concepts, fabrication methods, and separation performance for various types of emulsified oily water. Additionally, we present membrane-based strategies for simultaneous water purification and oil recovery from emulsified oily water. Finally, we identify current bottlenecks and propose future direction in this area, focusing on the development of next-generation superwetting membranes for comprehensive separation and zero discharge of true oily water at an industrial scale.

High-Flux Steady-State Demulsification of Oil-In-Water Emulsions by Superhydrophilic-Oleophobic Copper Foams with Ultra-Small Pores Under Pressure

3D superwetting materials struggle to maintain high-flux steady-state demulsification for oil-in-water emulsions because the accumulated oil within the material is difficult to discharge rapidly. The water flow shear force can swiftly remove the oil from the anti-fouling surface. In this study, by introducing nanofibers and carbon nanotubes and chemical modification, a superhydrophilic-oleophobic copper foam with pores of several micrometers is prepared, which can achieve a continuous demulsification process with steady-state flux over 57000 L m-2 h-1 for oil-in-water emulsions and rapid hydraulic-driven oil release under an additional pressure of 5 kPa. Thanks to the ultra-small pores of the copper foam, the steady-state demulsification efficiency can be still maintained at over 97.5%. During the demulsification process, the accumulation of oil and surfactants within the copper foam can be maintained at low levels, achieving dynamic equilibrium. With the aid of second-stage superhydrophilic copper mesh, the demulsified oil-water mixtures can be rapidly separated. This high-flux, steady-state, and efficient demulsification process shows great potential for industrial applications.

F-free etching and ingenious construction of hydrogel layer-prepared MXene membranes for oily wastewater separation

A strategy for the preparation of hydrogel layer MXene membranes by an F-free method was proposed. It maintained high permeance (2686.1 L m-2 h-1 bar-1) and separation efficiency (99.99%) even after 300 min of emulsion separation. The membrane resisted harsh chemical and microbiological environments and efficiently treated actual oily wastewater.