In recent years, superoleophobic-superhydrophilic materials have become popular in oil-water separation due to their special wettability. Since the surface tension of “oil” is much smaller than that of water, superoleophobic-superhydrophilic surfaces are difficult to prepare and most superoleophobic surfaces are superhydrophobic, which limits its application in oil-water separation.
In addition, surfactant-stabilized emulsified oil has small particle size (<10 μm) and high stability, and requires a complex demulsification process to achieve oil-water separation. Therefore, there is an urgent need for a simple, efficient, and environmentally friendly oil-water separation material to purify oily sewage.
Researchers Zeng Zhixiang, Wang Gang, He Yi and others from the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, prepared cellulose sponges with nanopores on the surface and macropores in the matrix through the dissolution and regeneration of cellulose and the occupancy of pore-forming agents to separate surface activity. Agent-stabilized oil-water emulsion.
This kind of sponge has special wettability that is lipophilic and hydrophilic in the air and superoleophobic underwater without chemical modification. In acid, alkali, and salt solutions, the contact angles of various oils are greater than 150° and the superoleophobic properties are stable. The nanopores on the surface of the sponge can effectively prevent the penetration of small-sized emulsified oil particles. The macroporous structure of the matrix and its super-hydrophilicity can ensure that the water phase quickly passes through the sponge matrix to achieve oil-water separation.
The prepared cellulose sponge shows high oil-water separation efficiency (>99.94%), water flux (91Lm-2h-1 gravity), and oil penetration resistance (can support a 22cm chloroform liquid column) in oil-water emulsion separation. ) and other characteristics. In addition, the cellulose sponge has self-cleaning ability, can effectively prevent oil contamination from being stained, and is highly reusable.
The above work has been published in GreenChemistry, a chemical journal of the Royal Society, 2015, 17(5): 3093-3099.
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