Magnetically Recyclable Graphene Oxide Demulsifier Adapting Wide pH Conditions on Detachment of Oil in the Crude Oil-in-Water Emulsion

In the present work, an amphiphilic and magnetically recyclable graphene oxide (MR-GO) demulsifier was devised and synthesized by graft of magnetic nanoparticles (Fe3O4@SiO2-APTES) and ethylenediamine on the GO surface. The wettability and surface charges of MR-GO under various pH conditions can be regulated via adjusting the contents and species of surface functional groups (such as amino, carboxyl, and hydroxyl). In the demulsificaition test, MR-GO displayed favorable demulsification performance for crude oil-in-water (O/W) emulsion under pH of 2.0-10.0, thusly greatly improving the application scope of common demulsifier. The optimal dosage of MR-GO was 200 mg/L and the demulsification efficiency attained a maximum value of 99.7% for crude O/W emulsion with pH of 6.0. What's more, owing to its magnetic response performance, the MR-GO can be reused and the demulsification efficiency remained above 91.0% after six cycles. Based on the strong interfacial activity, MR-GO can arrive to the crude oil-water interface. With the synergy effects of interfacial adsorption (pi-pi/n-pi) interactions and electrostatic attraction of demulsifier and interfacial films, and the aid of external mechanical forces, the interfacial films stabilized the emulsion were disrupted. Therefore, the oil droplets coated on the water droplets were gathered rapidly to form oily flocs and then migrated to the water surface to accomplish the demulsification of crude O/W emulsion.

Automated summary

An amphiphilic and magnetically recyclable graphene oxide demulsifier was synthesized by grafting magnetic nanoparticles and ethylenediamine onto the GO surface, exhibiting favorable demulsification performance for crude oil-in-water emulsions under various pH conditions. The MR-GO can be reused multiple times with consistent high demulsification efficiency. Through a combination of interfacial adsorption interactions, electrostatic attraction, and external mechanical forces, the demulsifier disrupts and stabilizes the emulsion interface, facilitating the rapid gathering of oil droplets to accomplish demulsification.