Recyclable and Magnetic Fe3O4@SiO2-Surfactant Nanoparticles for Rapid Demulsification and Enhanced Oil Recovery

Abstract A magnetically responsive nano-agent, Fe3O4@SiO2-BS12, was developed to improve the sustainability of chemical enhanced oil recovery. The nano-agent was designed to integrate effective oil-displacement capability with easy magnetic recovery for reuse. Characterization confirmed its core−shell structure, strong magnetism, and successful surfactant loading. Performance tests showed it could reduce interfacial tension to an ultra-low level (0.01 mN/m) while enabling effective emulsion separation under a magnetic field. Core flooding experiments verified its practical efficacy. Injection of the freshly prepared nano-agent following water flooding resulted in an additional 19.7% increase in total oil recovery. Notably, the nanoparticles were magnetically recovered and reused in a subsequent flood, still providing a significant incremental recovery of 17.9%. These results demonstrate a successful balance between high performance and recyclability. Overall, Fe3O4@SiO2-BS12 represents a promising reusable nano-fluid, offering a cost-effective and sustainable strategy for enhanced oil recovery through the integration of high displacement performance and a recoverable life cycle.