Treatment of oil-in-saltwater emulsions by in-situ production of magnetic FeOx nanoparticles

[Display omitted] •This investigation describes magnetic and chemical properties of in situ electrochemically produced FeOx preciptiates.•This approach is a proof-of-concept for leveraging the FeOx byproducts of electrocoagulation to improve effluent quality.•Findings indicate that iron oxides can be produced at ambient conditions via the electrocoagulation process.•Produced iron oxides are crystallites assignable to either Fe3O4 or γ-Fe2O3 and have measurable magnetic properties.•FeOx aggregates are proven to interact with the oil-in-water emulsion for removal of oil via an applied magnetic field. Oil-in-saltwater emulsions produced to simulate contaminated bilge water were successfully treated by electrochemical oxidation of iron anodes (electrocoagulation). Turbidity measurements of the as-prepared emulsions before and after treatment show a reduction in turbidity of over 98%, while application of a permanent magnet was found to be effective in reducing the settling time for the Fe-oxide containing sludge. Solution temperature was found to be the most critical parameter for influencing the efficiency of the electrocoagulation process, while electrode separation and solution contents (i.e. the presence of surfactants and oil) had less of an influence, especially for a solution temperature of 45 °C. Characterization of the Fe-oxide precipitates by electron microscopy, x-ray diffraction, and vibrating sample magnetometry confirmed that the products were nano-sized crystallites assignable to either Fe3O4 or γ-Fe2O3. All measurements indicated that a secondary phase was present which appeared as a varied particle morphology, a weak diffraction peak in some samples, and a reduced magnetic saturation. These results indicate that further optimization of the electrocoagulation process may be possible which could further improve the magnetic response of the Fe-oxide containing sludge.