Photocatalytic and sonophotocatalytic degradation of rhodamine B by nano-sized La2Ti2O7 oxides synthesized with sol-gel method

Abstract

Nano-sized La2Ti2O7 oxides were synthesized by sol-gel route. The photocatalytic properties of the Rhodamine B degradation on this photocatalyst were studied as a function of crystallite size, dye concentration, catalyst loading, temperature and intensity of UV light flux. The photocatalytic results as well as the microstructural analysis, carried out by X-ray Diffraction and Transmission Electron Microscopy, revealed a strong correlation between the apparent rate constant and the crystallite size/degree of crystallinity of the photocatalyst. Temperature studies have shown optimum photocatalysis at 40 °C. Measurements of the zeta potential as a function of pH made it possible to determine the point of zero charge of the photocatalyst at pH = 8 and to understand the influence of pH on the degradation of cationic or anionic pollutants. Finally, the sonophotocatalytic process was studied showing a noticeable improvement in the apparent rate constant, multiplied by a factor of ∼1.7 compared to photocatalysis alone. The synergistic effect was quantified via measurements in sonocatalysis alone and then coupled to UV irradiation. This synergistic effect is about 23 % in the case of degradation of Rhodamine B on La2Ti2O7 oxides synthesized at 1000 °C.