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With the rise of more and more industrial oil-bearing wastewater and the continual occurrence of oil spills, the demand for efficient oil-water separation materials and technologies has become increasingly urgent. It has been reported that magnetic nanoparticles with superhydrophobic/ulophilic properties can achieve oil-water separation. However, its separation efficiency is far from the actual use requirement. Although the oil-water separation efficiency of the composite particles can be improved through proper design, the advantage of high specific surface area of ​​the micro-nanoparticles is often overlooked. Moreover, due to poor dispersibility in water, conventional superhydrophobic/superlipophilic nanoparticles are not suitable for microemulsion separation.
The Polymer Self-Lubricating Composites Research Group of the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences recently developed a new type of polymer brush-grafted magnetic composite particles that can achieve efficient oil-water separation. The researchers grafted poly(N-isopropylacrylamide) (PNIPAM) onto silica-coated ferroferric oxide nanospheres to prepare polymer brush grafted magnetic composite particles using their special wettability. Apply it to oil-water separation.
Different from the gravity-driven oil-water separation, the polymer brush-grafted magnetic composite particles can be used as a solid stabilizer to diffuse into the oil-water interface region, and the oil-water contact interface is minimized through the volume exclusion effect. At the same time, the Pickering emulsion can be easily separated from the oil-water mixture under the action of an external magnetic field. When the emulsion is heated from room temperature to above the PNIPAM phase transition temperature (35°C), the wetting behavior of the PNIPAM is shifted and the Pickering emulsion loses its stability, releasing oil. Researchers have used toluene/water microemulsions as examples. The use of this material has achieved a high oil-water separation efficiency, and after repeated recycling, the composite particles can still maintain a high separation efficiency.
Compared with the traditional superhydrophobic/superhydrophilic particles for oil-water separation, this method utilizes PNIPAM's special wetting properties while giving full play to the advantages of high specific surface area of ​​micro-nanoparticles, greatly improving the oil-water separation efficiency of micro-nanoparticles. The new material is expected to be widely used in the oil-water separation field.
The above work was supported by the National Outstanding Young Scientists Fund and the National Natural Science Foundation. The research results were published in the recently published ACS Appl. Mater. Interfaces (Appl. Mater. Interfaces 2014, 6, 13334-13338).
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