Facile Low-Temperature Synthesis of a Bacillus subtilis-inspired Ionic Liquid Demulsifier with Multiple Hydrophilic Heads

Non-covalent interactions predominated by hydrogen bonding are of vital importance to the demulsification of oil-water emulsions. This study reports a Bacillus subtilis -inspired ionic liquid demulsifier (MEB-12) with multiple hydrogen-bonding sites for the treatment of oil-in-water (O/W) emulsions. The two hydrophobic “tails” of this demulsifier facilitate rapid migration within the emulsion and enable precise localization to the oil droplets, while the four symmetric hydrophilic head groups form a multivalent hydrophilic domain. This domain outcompetes interfacial asphaltenes by forming stronger multidentate hydrogen bonds with water molecules, mediated by its abundant ether, ester, and bromide hydrogen-bonding sites, thereby destabilizing the emulsion film. When treating O/W emulsions with an oil content of 0.2% at ambient temperature, MEB-12 at a concentration of 10   mg/L achieved a light transmittance (T %) of 98.4% and an oil removal efficiency (ORE) of 99.95%, demonstrating excellent demulsification performance at low dosage. Meanwhile, MEB-12 exhibited remarkable tolerance toward high salinity. To investigate the competitive adsorption mechanism between demulsifier and asphaltenes, zeta potential, dynamic interfacial tension, droplet coalescence time, and three-phase contact angle were employed as characterization techniques. Additionally, density functional theory was utilized to analyze the electrostatic potential on the molecular surface. Meanwhile, the independent gradient model based on Hirshfeld partition analysis and bond critical point were adopted to explore hydrogen bonding interactions. These characterization and computational simulation results demonstrated that MEB-12 exhibited excellent interfacial activity. Specifically, MEB-12 triggered the reconfiguration of the oil-water interfacial film via non-covalent interactions, thereby disintegrating the rigid film, promoting the coalescence of emulsified droplets, and achieving efficient demulsification.