Modified superhydrophobic magnetic Fe3O4 nanoparticles for removal of microplastics in liquid foods

Microplastics (MPs) stemming from plastic products have attracted wide attention around the world due to their stealth, persistence and potential threat to humans. It is essential to remove MPs by using eco-friendly and effective methods. In this study, to remove MPs, we proposed to prepare Fe3O4 superhydrophobic magnetic adsorbents (Fe3O4@Cn, n = 12, 14, 16, 18) modified by different saturated fatty acids (C12, C14, C16, C18) by liquid phase deposition method. Transmission electron microscope, atomic force microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry and nitrogen adsorption measurements were applied to characterize the morphology, functional groups, crystalline structures of Fe3O4@Cn as well as its magnetic properties and pore size distribution. It was shown that Fe3O4@Cn exhibited the characteristics of magnetic materials with superhydrophobic properties and thus possessed the ability to separate oil and water. During the removal of MPs in five liquid food systems, Fe3O4@C12 exhibited 92.89 % adsorption efficiency, which was ascribed to the electrostatic and chemical bonding interactions between MPs and Fe3O4@Cn, as suggested by density functional theory (DFT) calculations. In addition, the presence of organic matter in water can decrease the removal efficiency of Fe3O4@Cn due to the competitive adsorption effect. Simulation by Langmuir isotherm model suggested that Fe3O4@C12 displayed the greatest adsorption efficiency for Polystyrene (PS) (809.29 mg/g), which is higher than that of Fe3O4@C14, Fe3O4@C16, and Fe3O4@C18. In addition, Langmuir adsorption isotherm and Gaussian calculations suggested that PS was removed by Fe3O4@C12 through an exothermic reaction controlled by chemisorption. Overall, these results indicated that superhydrophobic magnetic materials prepared in this study show high potential for removing MPs in aqueous systems due to their low costs, good environmental friendliness, and high removal performance.