Selective Enrichment of Juglone in Walnut Green Peel Using Core-shell Magnetic Molecularly Imprinted Polymer

In this study, surface imprinting technology was used for the one-step preparation of a core-shell magnetic molecularly imprinted polymer (Fe3O4-NH2@MIP) with amino functionalized magnetic iron trioxide (Fe3O4-NH2) as the magnetic core at a mass ratio of juglone to functional monomer to cross-linking agent of 1:8:40. The structure, morphology and magnetic strength of the material were characterized by multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The adsorption performance was studied through dynamic adsorption and isothermal adsorption experiments. Results showed that an imprinted layer with a thickness of about 75 nm was successfully polymerized on the surface of Fe3O4-NH2, with a nearly spherical shape and a regular crystal structure and a saturation magnetic strength of 48.50 emu/g. The layer could be quickly separated in five seconds. When the adsorption time was 100 minutes and the concentration of juglone was 100 μg/mL, good adsorption performance was obtained with an adsorption capacity of 32.89 μg/mg, the kinetic adsorption process was closer to a pseudo-second-order model, and the adsorption data accorded with the Langmuir isotherm, indicating that Fe3O4-NH2@MIP enables efficient separation and enrichment of juglone from walnut green peel extract. This study is of reference significance for the development of more biological activity of juglone and the expansion of its application in food, pharmaceutical and other industries.