Fabrication of NiFe₂O₄ nanospheres-based magnetic fluid with enhanced magneto-responsive properties and sedimentation stability for rapid and efficient removal of oil spills

It is essential to remove the oil spills from the water surface and protect the marine environment and organisms. The commercial approaches for oil-water separation are seriously constrained by the high cost, low removal efficiency and potential secondary pollution. In the present work, we have reported a cost-effective, recyclable and environmental-friendly magnetorheological (MR) fluid for fast removal of oil spills from water surface. Successful fabrication of superhydrophobic NiFe₂O₄ nanospheres was achieved through a solvothermal strategy combining with a post-treatment process with octadecanoic acid. The synthesized NiFe₂O₄ nanospheres exhibited superparamagnetism, high saturation magnetization of 64.4 kA/m, large specific surface area of 12.9 m²/g, and small average pore diameter of 10.9 nm, which were strongly recommended as a dispersed phase for acquiring a high-performance MR fluid. The developed NiFe₂O₄ nanospheres-based MR fluid demonstrated the enhanced magnetic field-dependent rheological and viscoelastic properties as well as a remarkable sedimentation stability with a sedimentation ratio of 82.5 %. More importantly, such magnetic fluid was fully capable of realizing the rapid and efficient separation of oil spills from water surface and the maximum removal efficiency was determined to be about 96.3 %. Therefore, this work provides a promising candidate for oil spills clean-up with the unique characteristics of high oil removal efficiency, fast recovery and good recyclability.