Removal of oils from water surface via useful recyclable CoFe₂O₄/sawdust composites under magnetic field

Highlights: • Magnetic sawdust is used to remove oils from water surface. • Magnetic sawdust has high hydrophobicity and superoleophilicty. • Magnetic sawdust is easily controlled because of the magnetic character. • Magnetic sawdust possesses good chemical stability and excellent recyclability. In this study, the poplar sawdust was used as a recyclable, low cost, environmentally friend and highly selective oil absorbent material. The sawdust with high hydrophobicity, superoleophilicity and magnetic property was obtained by precipitating CoFe₂O₄ on sawdust surface and chemically modifying the low surface energy polysiloxane layers. These composites were able to absorb lubrication oil up to 11.5 times of the sawdust weight while completely repelling water. In addition, the oil-absorption composites were able to collect oils conveniently from water surface with the help of an external magnet due to its exceptional magnetic property. Furthermore, the sawdust could be cleared up and re-used for water–oil separation at least 10 times. This work provides a potential platform for developing a water-protection strategy using natural waste resources.