A novel TiO2/biochar composite catalysts for photocatalytic degradation of methyl orange.

A series of TiO2/biochar composite catalysts were prepared by the hydrolysis method for the degradation of methyl orange, where biochar was obtained from the pyrolysis of waste walnut shells. The catalysts were examined by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS), elemental analysis and ultra violet-visible diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic activity results showed that the catalysts noted as CT0.1/1, CT0.2/2 and CT 0.5/1 exhibited higher catalytic activity than that of pure TiO2. Besides, catalyst CT0.2/1 exhibited the highest catalytic activity (the decolorization efficiency of 96.88% and the mineralization efficiency of 83.23% were obtained), attributed to the synergistic effect of biochar and TiO2, while CT1/1 possessed the lowest activity due to the shelter of light by the excess biochar. After 5 repeated use, the catalyst CT0.2/1 still exhibited rather high activity toward the degradation of MO, where the decolorization efficiency and mineralization efficiency of MO achieved 92.45% and 76.56%, and the loss of activity was negligible.