Reusability of Photocatalytic CoFe₂O₄@ZnO Core-Shell Nanoparticles for Dye Degradation

The reusability of CoFe2O4@ZnO core-shell nanoparticles (NPs) for the photocatalytic degradation of methylene blue (MB) underUV radiation was successfully investigated. CoFe2O4@ZnO NPs with various CoFe2O4-to-ZnO concentration ratios weresynthesized as magnetic photocatalysts. The X-ray diffraction spectra showed that the NPs had a cubic spinel ferrite phase structureand a hexagonal wurtzite phase of ZnO. Fourier-transform infrared spectra showed the presence of Moct-O, Mtet-O, and Zn-O at593, 347-389, and 410-429 cm-1, respectively. The CoFe2O4@ZnO NPs had a saturation magnetization of approximately30 emu g-1 and a coercivity of approximately 280 Oe. The absorbance spectra showed that the absorbance peak ofthe CoFe2O4@ZnO NPs broadened and shifted to the right (higher wavelength) with increasing ZnO concentration.The CoFe2O4@ZnO NPs with higher ZnO concentrations exhibited higher photocatalytic activities and degradation rates. Theenhancement of MB degradation can be attributed to the formation of an internal structure between CoFe2O4 and ZnO. Thedegradation rate of CoFe2O4@ZnO decreased slightly after each successive recycle. The results indicated that the recycledCoFe2O4@ZnO NPs could be reused three times for photocatalytic degradation. As there is no significant decrease in thephotocatalytic degradation after four successive recycles, the CoFe2O4@ZnO NPs are suitable for application in dye degradation.