Dual Superlyophobic Copper Foam with Good Durability and Recyclability for High Flux, High Efficiency, and Continuous Oil–Water Separation

Abstract

Traditional oil-water separation materials have to own ultrahigh or ultralow surface energy. Thus, they can only be wetted by one of the two, oil or water. Our experiment here demonstrates that the wettability in oil-water mixtures can be tuned by oil and water initially. Hierarchical voids are built on commercial copper foams with the help of hydrothermally synthesized titanium dioxide nanorods. The foams can be easily wetted by both oil and water. The water prewetted foams are superhydrophilic and superoleophobic under oil-water mixtures, meanwhile the oil prewetted foams are superoleophilic and superhydrophobic. In this paper, many kinds of water-oil mixtures were separated by two foams, prewetted by corresponding oil or water, respectively, combining a straight tee in a high flux, high efficiency, and continuous mode. This research indicates that oil-water mixtures can be separated more eco-friendly and at lower cost.

A review of femtosecond laser-structured superhydrophobic or underwater superoleophobic porous surfaces/materials for efficient oil/water separation

“…The oil phase in the mixture is able to wet and penetrate through the membrane driven by superoleophilicity and gravity force, while water phase is prevented from passing through this membrane due to the superhydrophobicity of the membrane surface. [11][12][13][14][15][16][17][18]37,44,[172][173][174][175][176][177][178][179][180][181][182][183] As a result, oil is removed from the mixture; that is, the OWM is separated. Regarding the underwater superoleophobic porous membranes (such as metal meshes, fabrics, bers, polymer membranes, etc.…”

“…Zhou et al prepared a kind of titanium dioxide nanorods-structured copper foams by hydrothermal deposition. 174 Both water and oil could easily wet and be absorbed by the resultant foam. However, the foam was superhydrophobic underwater oil.…”

Mussel‐Inspired Dual‐Superlyophobic Biomass Membranes for Selective Oil/Water Separation

“…The porous construction of the membrane formed by the fibers was retained after the homogeneous coating of nanoparticles of around 100 nm in sizes (Figure 2B,D). These hierarchical morphologies of the as‐prepared fibers are expected to enhance the trapping and formation of a stable layer of prewetted liquids . The colors of raw cotton and kapok fibers changed from white (cotton) and light gray (kapok) to dark brown, substantiating the growth of PDA on the fibers .…”

“…Specifically, “oil‐penetrating” membranes with underoil superhydrophobicity are able to retain water, and “water‐penetrating” membranes with underwater superoleophobicity functions to retain oil . The underoil superhydrophobic state (UO‐SHB) normally displays “lotus effect,” which requires low surface energy, and the underwater superoleophobic (UW‐SOB) property demands high surface energy, which is similar to “fish‐scale effect.” In principle, the underoil water contact angle (CA w/o ) and underwater oil contact angle (CA o/w ) sum up to 180° on a solid surface . Under the thermodynamic point of view, these two properties are not expected to simultaneously appear on the same surface.…”

Trifunctional Copper Mesh for Integrated Oil/Water Separation, SERS Detection, and Pollutant Degradation

“…Therefore, the detection of pollutants and the purification of contaminated water have drawn much attention in recent years . Many excellent researchers have devoted into developing various oil/water separating materials to clean organic compounds from water sources, such as nanofibers, metal foams, polymer sponges, metal meshes, membrane, and aerogels . Among above materials, copper meshes have been paid much attention due to their big voids, good mechanical stability, high separation efficiency, and stable durability .…”