Synthesis of La2O3-NiO photocatalyst and kinetics of degradation of dye wastewater under visible light irradiation

The novel photocatalyst, La₂O₃-NiO, was prepared by sol-gel with nickel nitrate hexahydrate and lanthanum salt, characterized by means of XRD and SEM. Its photocatalytic activities were evaluated by degradation of Direct Bordeaux (DB) solution as a simulated dye wastewater under daylight irradiation. The results show that Pure and La-doped MO are a cubic perovskite structure with space group Fm-3m (225). A small amount of perovskite-like structure of La_xNiO_y exists in composite structure of La₂O₃-NiO. The porous and well-fracture photocatalyst particles are composed of nanometer grains about 15.9 nm, which contributes to the increase of photocatalytic efficiency. After 180 min of exposure to the daylight in the presence of 3% La₂O₃-NiO, the degradation rates of DB are 71.9% much higher than un-doped samples (27.1%). The catalyst surface reaction rate constants (Kr) are 3.88 ×10^-2 mg-min-1·L^-1 for degradation at 30 mg·L^-1 of DB under daylight irradiation.