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

In this study, an innovative magnetic demulsifler (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 demulsifler dosage (MDdose), the concentration of oil (C-oil), pH, the concentration of the surfactant (C-sur), and separation time (t(sep)) on the demulsification efficiency (%eta(dem)), and the percentage of oil recovered (%R-oil) were evaluated. An excellent %eta(dem) >= 90% was achieved C(oil )in the range 50 -2000 mg/L. Using an MDdose as low as 10 mg/L attained a %eta(dem) in the range of 93%-94.3% for O/W mixtures with C-oil < 2000 mg/L, which slightly decreased to similar 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 %eta(dem) of similar to 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 demulsiflers. (C) 2020 The Author(s). Published by Elsevier Ltd.