Investigation into the synergy at interfaces and recyclability of functional magnetic reed biochar-based demulsifying agents

To tackle the challenges of non-recyclability and environmental hazards posed by conventional polyamine demulsifiers, this research has adopted reed sourced from oil fields as the primary material. Specifically, by leveraging an in-situ pyrolysis-co-precipitation approach, we synthesized magnetic biochar (MBC) and grafted polyamine molecules using KH-570, developing a composite demulsifier (MPRB) with interfacial activity and magnetic responsiveness. Material characterization indicated that MBC features a hierarchical porous structure characterized by a specific surface area of 372 m 2 ∙g -1 . Moreover, it also contains ultra-high magnetic Fe 3 O 4 nanocrystals, which boast a saturation magnetization of 39.87 emu∙g -1 . As a result, this configuration enhances the magnetic response rate by 40% relative to conventional carriers. Post-functional modification, MPRB, capitalizing on the synergistic effect of mesoporous confinement and the amphiphilic nature of polyamine groups, significantly reduced the interfacial tension of emulsions from 42.29 mN∙m -1 to 26.02 mN∙m -1 . Additionally, it adjusted the surface wettability to achieve an amphiphilic balanced state, evidenced by a water contact angle of 87.3°. Demulsification experiments revealed that MPRB-3, when subjected to conditions of 70°C and 400 mg∙L -1 , displayed time-dependent demulsification efficiency for high-viscosity crude oil emulsions and diesel emulsions. After 60 min, the demulsification rates were 85.23% and 96.23%, respectively, which increased to 90.72% and 98.28% after 120 min. Following rapid separation facilitated by an external magnetic field within 25 s, the demulsification rates sustained at 85.82% and 93.82% even after six cycles of reuse. This durability is attributed to the high retention rate of the Fe 3 O 4 magnetic core and the minimal structural degradation of the biochar framework. Through the synergistic enhancement of interfacial activity and the integration of magnetic separation technology, this study achieves a green, full-process chain for demulsifiers, including efficient demulsification, rapid recovery, and recyclable regeneration, offering an eco-friendly solution for oil field produced liquids management and aligning with sustainability.