Fast demulsification of oil-water emulsions at room temperature by functionalized magnetic nanoparticles

Oil-water emulsions separation is a significant and intractable problem in many industrial processes, especially in petroleum industry. To deal with the demulsification of oil–water emulsions, a novel kind of amphiphilic magnetic demulsifier (M-ANP) has been designed and successfully synthesized by grafting aliphatic alcohol nonionic propylene oxide-ethylene oxide block polyether (ANP) (~22.3 mg/g) onto the surface of epoxy-functionalized magnetite (Fe3O4) nanoparticles (~9.1 nm). The physicochemical and interfacial properties of M-ANP have been characterized and analyzed. The bottle tests show that the M-ANP performs well in fast (less than 5 min) and relatively complete demulsifying (up to 95.5%) both water-in-oil emulsions (water-in-crude oil, water-in-bitumen) and oil-in-water emulsions (diesel-in-water, crude oil-in-water, etc.) under room temperature. It also works well in breaking the stable water-in-asphaltene emulsions, achieving the demulsification efficiency of 90.0% within 2 min without heating (at 2000 ppm of M-ANP). Mechanistic study shows that the ANP and magnetic nanoparticles work synergistically in emulsions separation. The hydrophilic polyethylene oxide segments in the ANP would form hydrogen bonds with water, facilitating the interfacial adsorption of M-ANP. Furthermore, the multi-functional characteristics of magnetic nanoparticles (nano size, magnetic response and high density) promote the transfer of nanoparticles in dispersed phase and enhance the gravity settling and magnetic separation process of coalesced droplets. This kind of nanoparticle demulsifier would serve for promising applications in a variety of industrial and environmental processes at an energy-saving way.