A three-dimensional polyoxometalate/graphene aerogel as a highly efficient and recyclable absorbent for oil/water separation
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摘要: 三维石墨烯气凝胶具有可调控的孔结构、大的比表面积、优异的压缩性、弹性和润湿性,是一种高效的油水分离吸附剂。然而,三维石墨烯气凝胶的制备方法通常包括高温过程,导致高成本、能耗高和耗时长。本文以磷钼酸为交联剂和促进剂,水合肼为还原剂,在室温条件下同时将氧化石墨烯还原与自组装,制备出三维多孔的多金属氧酸盐复合石墨烯气凝胶(POM-GA),并证明其是一种高效、可回收的油水分离吸收剂。研究表明,POM-GA具有三维连通的多孔结构、大的比表面积、优异的压缩性、弹性和润湿性,对不同的有机溶剂具有良好的吸附能力(100~210 g g−1),可快速去除水中的各种有机污染物,优于先前报道的大多数高温合成的石墨烯基宏观组装体。经10次吸附-挤压和吸附-挤压-燃烧循环后,POM-GA的吸油量保持率分别达到96%和90%。因此,三维POM-GA具有广泛的适用性和优异的耐用性,在高效油水分离方面具有良好的应用前景。Abstract: Three-dimensional (3D) graphene aerogels (GAs) with a tunable pore structure, a highly accessible surface area, and exceptional compressibility, elasticity and wettability have been explored as promising absorbents for efficient oil/water separation. However, the strategies for assembling 3D GAs usually involve a high-temperature process, resulting in high cost. We report the synthesis of a 3D porous polyoxometalate (POM)-hybridized GA (POM-GA) as a highly efficient and recyclable absorbent for oil/water separation. The material was fabricated at room temperature by the self-assembly and reduction of graphene oxide using POM as a functional cross-linker and hydrazine hydrate as a reductant. It had a 3D interconnected macroporous structure, a large specific surface area, and exceptional compressibility, elasticity and wettability, and had excellent absorption capacities of 100-210 g g−1 for the rapid removal of various organic pollutants from water, outperforming most of the previously reported graphene-based macro-assemblies synthesized at high temperatures. Moreover, the absorbed oils can be readily removed by squeezing or first squeezing and then burning the remaining organic from the 3D POM-GA. The oil-absorption capacity retention rates of the 3D POM-GA are 96 and 90% after 10 absorbing-squeezing and absorbing-squeezing-burning cycles, respectively. The material therefore has great potential for efficient oil/water separation with wide applicability and excellent durability.
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Key words:
- Graphene /
- Three-dimensional /
- Graphene aerogels /
- Oil/water separation
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Figure 2. Morphological and structural characterization of 3D POM-GA: (a,b) Photographs of POM-GAs (a) held by a tweezer and (b) supported on a flower, (c) SEM image, (d) nitrogen adsorption and desorption isotherms and the pore size distribution (inset), (e) TGA curve of POM-GA, (f) XRD patterns and (g) Raman spectra of POM-GA and GO.
Figure 3. The wettability and mechanical compressibility of 3D POM-GA: (a) photograph of 3D POM-GA under the water, (b) photograph of water and methylbenzene droplets on the surface of 3D POM-GA, (c,d) contact angles of 3D POM-GA with (c) water, and (d) methylbenzene and (e) reversible mechanical compressibility and elasticity of 3D POM-GA.
Figure 4. Absorption performance of 3D POM-GA: (a,b) removal of (a) methylbenzene on the water surface and (b) dichloromethane from the water bottom by 3D POM-GA, (c) adsorption capacities for various organic liquids and (d) a comparison of 3D POM-GA with various 3D porous absorbents for absorption of organic solvents.
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