Application of Fe3O4 magnetite nanoparticles grafted in silica (SiO2) for oil recovery from oil in water emulsions

Abstract

In this study, an innovative magnetic demulsifier (MD) was prepared by grafting a silica layer onto the surface of the Fe3O4 magnetic nanoparticles (MNPs) using the modified Stober process. The MD was characterized using various analytical techniques (XRD, FTIR, TGA, TEM, VSM, etc.) and employed to recover oil from O/W emulsion, which were then regenerated and recycled several times. The effects of magnetic demulsifier dosage (MDdose), the concentration of oil (Coil), pH, the concentration of the surfactant (Csur), and separation time (tsep) on the demulsification efficiency (%ηdem), and the percentage of oil recovered (%Roil) were evaluated. An excellent %ηdem ≥ 90% was achieved Coil in the range 50–2000 mg/L. Using an MDdose as low as 10 mg/L attained a %ηdem in the range of 93%–94.3% for O/W mixtures with Coil < 2000 mg/L, which slightly decreased to ∼90% for higher concentrations. The reported %Roil (p-value <0.05) was >90 ± 0.1 for tests carried out with pH ≤ 7 and Csur ≤ 0.1 g/L and declined at higher pH and Csur to % 86.5 due to the increase in emulsion stability. The developed MD exhibited high recyclability at an effective and stable %Roil and %ηdem of ∼90% and 86.4% after 9 cycles, respectively. Demulsification process best fits the combined Langmuir-Freundlich (L-F) isotherm with highest adsorption capacity (Qmax) of 186.0 ± 5 mgoil/gMD compared to 86.0 ± 5 mgoil/gMD for Fe3O4, which is 1.1 folds greater than Qmax reported in the literature for other demulsifiers.