Desert beetle-like microstructures bridged by magnetic Fe3O4 grains for enhancing oil-in-water emulsion separation performance and solar-assisted recyclability of graphene oxide

Owing to its high selective adsorption and excellent cyclability, superwetting materials have attracted considerable attention in environmental governance, especially oily wastewater treatment. However, the inferior separation efficiency and high recovery energy consumption seriously limit the actual application of superwetting particles in oil–water emulsion separation. Herein, inspired reversely by the water collection and water retention of the hydrophilic/superhydrophobic structure on the Stenocara beetle’s back, we fabricated magnetic graphene oxide composite with beetle-like microstructure by one-step solvothermal and environmentally friendly ball milling method. Magnetic composite with superhydrophobic/superoleophilic bumps–hydrophilic underlayer exhibits high hydrophobicity/oleophilicity in air and high oleophobicity underwater. In the process of particle assembly, the Fe3O4 grains with abundant oxygen vacancies peeled off from the in-situ deposited magnetic Fe3O4 microspheres play a bridging role to immobilize the superhydrophobic carbon black particles on the graphene oxide (GO) surface. On the unique surface of magnetic composite, attributed to strong π–π/n–π interface adsorption and hydrophobic interaction, the oil–water separation can be rapidly demulsified and the superoleophilic bumps (superhydrophobic carbon black nanoparticles) can capture and aggregate tiny oil droplets. The hydration layer formed in the hydrophilic region effectively prevents the captured oil droplets from spreading on the composite structure, thus enhancing the emulsion separation ability of magnetic GO. More importantly, the prepared composites exhibit efficient recycling and regeneration under solar irradiation, which is superior to the recovery efficiency of traditional GO sheets lacking high self-heating components. These inverse beetle-like magnetic GO-based particles open up a new opportunity for the design and fabrication of advanced demulsifiers in the field of oil–water emulsion separation.