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 (MD_dose), the concentration of oil (C_oil), pH, the concentration of the surfactant (C_sur), and separation time (t_sep) on the demulsification efficiency (%η_dem), and the percentage of oil recovered (%R_oil) were evaluated. An excellent %η_dem ≥ 90% was achieved C_oil in the range 50-2000 mg/L. Using an MD_dose as low as 10 mg/L attained a %η_dem in the range of 93%-94.3% for O/W mixtures with C_oil < 2000 mg/L, which slightly decreased to ∼90% for higher concentrations. The reported %R_oil (p-value <0.05) was >90 ± 0.1 for tests carried out with pH ≤ 7 and C_sur ≤ 0.1 g/L and declined at higher pH and C_sur to % 86.5 due to the increase in emulsion stability. The developed MD exhibited high recyclability at an effective and stable %R_oil and %η_dem of ∼90% and 86.4% after 9 cycles, respectively. Demulsification process best fits the combined Langmuir-Freundlich (L-F) isotherm with highest adsorption capacity (Q_max) of 186.0 ± 5 mg_oil/g_MD compared to 86.0 ± 5 mg_oil/g_MD for Fe₃O₄, which is 1.1 folds greater than Q_max reported in the literature for other demulsifiers.

Keywords: Demulsification efficiency; Fe(3)O(4)–SiO(2) nanoparticles; Oil in water (O/W) emulsion; Oil removal.