Reusability of Photocatalytic CoFe 2 O 4 @ZnO Core–Shell Nanoparticles for Dye Degradation

Abstract

The reusability of CoFe 2 O 4 @ZnO core–shell nanoparticles (NPs) for the photocatalytic degradation of methylene blue (MB) under UV radiation was successfully investigated. CoFe 2 O 4 @ZnO NPs with various CoFe 2 O 4 –to–ZnO concentration ratios were synthesized as magnetic photocatalysts. The X-ray diffraction spectra showed that the NPs had a cubic spinel ferrite phase structure and a hexagonal wurtzite phase of ZnO. Fourier-transform infrared spectra showed the presence of M oct -O, M tet -O, and Zn–O at 593, 347–389, and 410–429 cm −1 , respectively. The CoFe 2 O 4 @ZnO NPs had a saturation magnetization of approximately 30 emu g −1 and a coercivity of approximately 280 Oe. The absorbance spectra showed that the absorbance peak of the CoFe 2 O 4 @ZnO NPs broadened and shifted to the right (higher wavelength) with increasing ZnO concentration. The CoFe 2 O 4 @ZnO NPs with higher ZnO concentrations exhibited higher photocatalytic activities and degradation rates. The enhancement of MB degradation can be attributed to the formation of an internal structure between CoFe 2 O 4 and ZnO. The degradation rate of CoFe 2 O 4 @ZnO decreased slightly after each successive recycle. The results indicated that the recycled CoFe 2 O 4 @ZnO NPs could be reused three times for photocatalytic degradation. As there is no significant decrease in the photocatalytic degradation after four successive recycles, the CoFe 2 O 4 @ZnO NPs are suitable for application in dye degradation.