Cellulose Sponge with Superhydrophilicity and High Oleophobicity Both in Air and under Water for Efficient Oil–Water Emulsion Separation

Abstract

Oil–water emulsions stabilized by surfactants are fine dispersions of oil in water or of water in oil and difficult to separate which will lead to serious water pollution. A more recent development is the ability to fabricate oleophobic–hydrophilic surfaces in air, which are not easy to construct due to the difference surface tension between water and oil. Herein, a cellulose sponge with multipore structure is fabricated to increase the removal efficiency. Amphiphilic molecular brushes of polyethylene glycol with short perfluorinated end caps (F‐PEG) are grafted on cellulose sponges to solve the contradictory relation of hydrophilicity and oleophobicity and improve oil/water selective wettability and fouling resistance. Besides, stable superhydrophilicity and superoleophobicity under water, corrosive liquids, and high oleophobicity in air conditions are exhibited in the F‐PEG grafted porous cellulose sponges with textured surfaces (F‐g‐CS). And the separation efficiency and rate of F‐g‐CS with surface of nanopores are 99.92% and 180 L m−2 h−1, while that of micropores are 99.83% and 297 L m−2 h−1 only under gravity. It is demonstrated that the grafting F‐PEG molecules imparted F‐g‐CS of micropores surface with high flux and separation efficiency simultaneously. Furthermore, antifouling property and collection of water in oil–water mixture without fouling are possessed in F‐g‐CS.

Hydrophilic–Oleophobic, Macroporous Polymers Enabled by In-Situ Polymerization and Foaming for Removing Water from Oils

“…The selective absorption and the removal of water from the water–hexadecane mixture could be resulted from underoil hydrophilicity. The underoil hydrophilic TG x are promising for removing a small amount of water from oil–water mixtures, and are advantageous over the conventional hydrophilic materials, in which prewetting by water is required. , …”

“…The underoil hydrophilic TGx are promising for removing a small amount of water from oil−water mixtures, and are advantageous over the conventional hydrophilic materials, in which prewetting by water is required. 31,32 The underoil hydrophilic TGx are also found suitable for removing water from surfactant-stabilized, w/o emulsions that were used as a model for w/o emulsions generated from moisture condensation, owing to temperature and/or humidity variation, and from reclaimed oils via absorption or filtration. A small amount of water in the oils (such as diesel) might cause serious damage to engines and pollution the environment, and thus should be removed.…”

Emulsion-Templated, Magnetic, Hydrophilic–Oleophobic Composites for Controlled Water Removal

“…As a result, the fabrication of hydrophilic–oleophobic surfaces is usually a challenge. Recently, hydrophilic–oleophobic porous materials have been developed by fabricating heterogeneous surfaces through coating an oleophobic layer, fluorine-chain containing layer, onto a hydrophilic porous matrix. − However, the method for hydrophilic–oleophobic porous material preparation is facing problems, including pore clogging and uneven coating to the inner surfaces.…”

MWCNTs polyurethane sponges with enhanced super-hydrophobicity for selective oil–water separation

“…Incineration causes severe energy loss, while generating dangerous air pollution [9]; and the surface skimming method is costly, time consuming, and provides low separation efficiency. Traditional absorption resources for oil/water separation are mostly microporous materials, such as activated carbon [10], zeolite [11], cellulose [12], wool [13], and modified clay [14]. However, due to their poor adsorption performance, low recyclability, and adsorption selectivity, the application of these material types is limited.…”