Effect of modified γ-Fe2O3 magnetic nanoparticles on the stability of heavy oil-in-water emulsions

The effects of modified γ-Fe2O3 magnetic nanoparticles having various sizes at different mass fractions on the stability of heavy oil-in-water emulsions were compared. The zeta potential, wettability, oil-water interfacial tension, apparent viscosity, and oil droplet distribution of the emulsions were measured. The optimal size of the γ-Fe2O3(-COOH) magnetic nanoparticles was 2–3 μm, and this resulted in the lowest water-separation rate (23.72% at 4 hours), greatest electrostatic repulsion, weakest hydrophilic effect, lowest interfacial tension, greatest migration resistance, and smallest and most uniform oil droplet distribution. In addition, the stability of the emulsions increased and then decreased as the mass fraction of γ-Fe2O3 (-COOH) magnetic nanoparticles increased because of the increased electrostatic repulsion and decreased migration resistance. This in-depth analysis of the effect of modified magnetic nanoparticle size on the stability of oil-in-water emulsions provides comprehensive theoretical support for achieving viscosity and resistance reduction in an environmentally friendly manner.