Bisulfite assisted photocatalytic degradation of methylene blue by Ni-Fe-Mn oxide from MnO4 intercalated LDH

A novel composite of Ni-Fe-Mn ternary metal oxide (Mn-LDO) was synthesized by MnO4- intercalation into NiFe-LDH and calcination to improve photocatalytic efficiency. The conventional Ni-Fe binary metal oxide (C-LDO) prepared from Ni-Fe-LDH was also employed for comparison. Bisulfite was added to the above oxides in order to improve the photocatalytic degradation during the reaction. The as-synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), Brunauer, Emmett, and Teller (BET), UV-Vis diffuse reflectance spectroscopy and X-ray photoelectron spectra (XPS). Photocatalytic activities of these catalysts were evaluated for methylene blue (MB) degradation under the visible light with and without the assistance of NaHSO3. The results indicated that Mn-LDO showed superior photocatalytic decomposition capability of MB than that of C-LDO. Moreover, Mn-LDO showed much higher photocatalytic degradation efficiency of MB in the presence of NaHSO3 than only the single Mn-LDO degradation system. The stability and recyclability of the catalyst were also investigated.