Insight into the influence of morphology and structure of Fe3O4 nanoparticles on demulsification efficiencies

Abstract

Functional Fe3O4 nanoparticle (Fe3O4 NP) is one of the most attractive candidates in the demulsification field because of its outstanding recycling ability, low cytotoxicity, and good biocompatibility. However, the lack of research on their interfacial properties greatly inhibits further development in the industrial demulsification process. The main aim of this work is to explore interfacial properties of functional Fe3O4 NPs from their intrinsic natures, namely morphologies and structures. Three Fe3O4 NPs with different morphologies, including triangle-shaped Fe3O4 NPs (TF NPs), octahedron-shaped Fe3O4 NPs (OF NPs) and truncated octahedron-shaped Fe3O4 NPs (TOF NPs), were prepared by using the solvothermal reaction. Their demulsification capacities of water-in-cyclohexane (W/C) emulsion were evaluated and the TOF NPs had best performance. The demulsification process including diffusion, adsorption and phase separation stages of these Fe3O4 NPs were investigated in detail by interfacial experiments and mathematical models for explain the demulsification result. The diffusion coefficient was calculated at both the early and late stages of the demulsification process, along with their adsorption energy and the elastic modulus of oil-water interfaces. TOF NPs had the largest diffusion coefficient of 1.777 × 10−6 and 2.443 × 10−6 m2/s at the early and late stages, respectively. The W/C interface adsorption energy of TOF NPs were much lower than that of the others and the elastic modulus of W/C interface reduced by TOF NPs was also more effective than that by the others.