Magnetically retrievable and reusable BiVO4/Li0.5Fe2.5O4 nanocomposites for photocatalytic disintegration of methylene blue

BiVO4 (BVO) and Li0.5Fe2.5O4 (LFO) semiconducting ceramic oxides were synthesized by solid state and auto-combustion methods, respectively. Three different magnetic composites (BVO25/LFO75, BVO50/LFO50 and BVO75/LFO25) between BVO and LFO were prepared and characterized systematically using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), Transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and vibrating-sample magnetometer (VSM technique). PXRD studies confirmed the formation of single phase BVO, LFO and the composites. SEM analysis revealed the irregular shaped particles of the samples with average sizes similar to 70 nm. As confirmed from the magnetic measurements using VSM, all composites were found to be magnetic in nature and the magnetization decreases with increasing BVO content in the composites. Using DRS, band gaps of all samples were estimated and are in the visible region (2.09-2.37 eV). All samples were employed as photocatalysts for the degradation of methylene blue under visible light irradiation and the rate of degradation has been monitored using UV-Vis spectroscopy. The nanocomposite with 50 wt% BVO + 50 wt% LFO exhibited maximum efficiency in the presence of H2O2. The catalyst can be retrievable magnetically and reusable up to 5 cycles, without considerable drop in its activity.