Application of FeO magnetite nanoparticles grafted in silica (SiO) for oil recovery from oil in water emulsions.

In this study, an innovative magnetic demulsifier (MD) was prepared by grafting a silica layer onto the surface of the FeO 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), the concentration of oil (C), pH, the concentration of the surfactant (C), and separation time (t) on the demulsification efficiency (%η), and the percentage of oil recovered (%R) were evaluated. An excellent %η ≥ 90% was achieved C in the range 50-2000 mg/L. Using an MD as low as 10 mg/L attained a %η in the range of 93%-94.3% for O/W mixtures with C < 2000 mg/L, which slightly decreased to ∼90% for higher concentrations. The reported %R (p-value <0.05) was >90 ± 0.1 for tests carried out with pH ≤ 7 and C ≤ 0.1 g/L and declined at higher pH and C to % 86.5 due to the increase in emulsion stability. The developed MD exhibited high recyclability at an effective and stable %R and %η 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) of 186.0 ± 5 mg/g compared to 86.0 ± 5 mg/g for FeO, which is 1.1 folds greater than Q reported in the literature for other demulsifiers.