Surface polarity-regulated hydrogen bond reconstruction in superparamagnetic Fe3O4 nanoparticles for ultra-fast demulsification of water-in-heavy oil emulsions at room temperature

Abstract

This study aims to address the issue of efficient demulsification of water-in-heavy oil emulsions (W/HO-Es) in the petroleum industry. Herein, the novel amphiphilic polymer-modified superparamagnetic Fe₃O₄ NPs (ap-Fe₃O₄) were prepared using interface engineering strategies. The ap-Fe₃O₄ nanoparticles prepared have an average particle size of 9.52 nm. Its surfaces are rich in various polar groups (such as carboxyl, hydroxyl, and amino groups), which significantly enhance their surface polarity. The ap-Fe₃O₄ NPs exhibit ultra-high demulsification efficiency for interfacially active asphaltenes (IAA)-stabilized W/HO-Es. Experimental results demonstrated that ap-Fe₃O₄ could completely remove water from W/HO-Es at 2000 ppm within 30 s at room temperature, achieving a demulsification efficiency of 100 %. Microscopic visual characterization and multi-scale theoretical calculations reveal that the outstanding demulsification performance of ap-Fe₃O₄ is due to the “surface polarity enhanced hydrogen bond reconstruction” effect at the heavy oil–water interface. This enhancement allows ap-Fe₃O₄, with its high interfacial activity, to effectively disrupt the hydrogen bonds and π-π stacking of IAA at the heavy oil–water interface. This disruption breaks down the IAA films, promotes the coalescence and aggregation of water molecules, and ultimately achieves efficient demulsification of W/HO-Es. This research provides a new approach for regulating the surface hydrogen bonding of magnetic Fe₃O₄ NPs and establishes a solid theoretical foundation for the further development of revolutionary new magnetic demulsification materials.