Synthesis of magnetic nanoparticles (Fe3O4) coated with fatty acids and surfactants and their application in demulsification of crude oil and water emulsions

Crude oil is released into the water sources during exploration, extraction or displacement operations due to the partial dissolution, and it can remain as a layer on the surface of the water or become emulsive. Crude oil emulsion is very stable due to the presence of asphaltene and cannot be removed by the common methods. In this research, iron oxide nanoparticles were coated with oleic acid (OA), stearic acid (SA), sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP) and polyoxyethylene (POE), by using the same method. After synthesizing iron oxide nanoparticles and coating their surface with fatty acids and surfactants, we have tried to break the crude oil emulsion in water and remove the crude oil from the environment by adsorption via these nanoparticles. Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), vibration sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Zeta potential devices were used to identify nanoparticles and their characteristics. Demulsification of crude oil in water (O/W) with nanoparticles coated with fatty acids and surfactants was studied. UV-Vis spectrophotometery was used to determine the amount of crude oil adsorption by nanoparticles. From the results, the nanoparticles coated with the fatty acids with smaller chains could more absorb the crude oil. The highest adsorption (98.03 %) was recorded for iron oxide nanoparticles coated with polyoxyethylene (Fe3O4@POE) and the lowest percentage (46.69 %) is related to the nanoparticles coated with palmitic acid in an alkaline medium. Alkalinization of the medium while coating the nanoparticles with fatty acid has increased only the efficiency in the case of oleic acid while led to a significant decrease in the efficiency for palmitic and stearic acids compared to the neutral state.