Effects of calcination temperature on characterization and photocatalytic activity of La2Ti2O7 supported on HZSM-5 zeolite

The effects of calcination temperature on properties of 70%La2Ti2O7/HZSM-5 prepared by sol-gel method were studied. Photocatalytic degradation of Reactive Brilliant Red X3B on the materials was measured. The supported La2Ti2O7 tends to disperse on the surface of HZSM-5 particles in 70%La2Ti2O7/HZSM-5 composites. The majority phase of lanthanum titanate, monoclinic La2Ti2O7, forms in the material at 800 °C, while a small amount of orthorhombic La4Ti9O24 appears at 900 °C. The crystallite sizes of La2Ti2O7 are 24.5, 29.9 and 42.0 nm in the samples calcinated at 800, 900 and 1000 °C, respectively. The band gaps of 70%La2Ti2O7/HZSM-5 is gradually reduced with the increase of calcination temperature up to 900 °C, due to the quantum size effect along with crystal growth at high temperature. BET surface area of the composite gradually decreases with rising calcination temperature. The maximum photocatalytic acitvity is found on 70%La2Ti2O7/HZSM-5 calcinated at 800 °C, which is in accordance to production of hydroxyl radical under irradiation. 73.7% of the initial photocatalytic activity is still retained when the material is reused for the fifth time.