Carbon Nanofiber Aerogel/Magnetic Core–Shell Nanoparticle Composites as Recyclable Oil Sorbents

Developing sorbent materials for the removal of oil spills has become an attractive research topic in recent years for its impact on environmental and ecological concerns. The sorbents should be light, low cost, oil selective, environmentally friendly, mechanically robust, easily collected and recyclable, as well having high absorption capacities. Here, magnetic carbon nanofiber (MCF) aerogels have been developed from bacterial cellulose-based nanocomposites as efficient and recyclable oil sorbents. The MCF aerogels comprise a 3D interconnected structure of carbon nanofibers, with very high porosity, decorated with uniformly dispersed magnetic nanoparticles (NPs), with an Fe/Fe3O4 core-shell structure. The MCF aerogels exhibit very high magnetization (>100 emu g-1), compared to other previously reported magnetic aerogels, due to the Fe core/Fe3O4 shell NPs, but additionally with an ultralow density of only 7 mg cm-3. Furthermore, the MCF aerogel is highly compressible up to 90% strain and instantly returns to the original shape after release without any plastic deformation. It is also highly durable, up to 100 compressive stress-strain cycles. As for oil sorbents, the MCF aerogel can absorb oils directly without any post-surface treatment, due to its hydrophobic/oleophilic property. The absorption capacities are in the range of 37-87 g/g for various types of oils and organic solvents. These values are comparably large amongst magnetic carbon aerogels. Additionally, due to their large magnetization, the MCF aerogels can be easily manipulated during oil absorption and collected via external magnetic fields, which is beneficial for avoiding direct contact with possible hazardous solvents. They can then be recycled several times by dissolution with hardly any reduction in absorption capacity. This work has demonstrated that environmentally friendly biomass-derived MCF aerogels could be candidates for the absorption and recycling of oils and organic solvents from wastewater.