Low frequency ultrasound (42 kHz) assisted degradation of Acid Blue 113 in the presence of visible light driven rare earth nanoclusters loaded TiO2 nanophotocatalysts

An attempt has been made to render the visible light driven photocatalytic activity to the TiO₂ nanocatalysts by loading 1 wt% of rare earth (RE) nanoclusters (Gd³⁺, Nd³⁺ and Y³⁺) using a low frequency (42 kHz) producing commercial sonicator. The STEM-HAADF analysis confirms that the RE nanoclusters were residing at the surface of the TiO₂. Transmission electron microscopic (TEM) and X-ray diffraction (XRD) analyses confirm that the loading of RE nanoclusters cannot make any significant changes in the crystal structure of TiO₂. However, the optical properties of the resulted nanocatalysts were significantly modified and the nanocatalysts were employed to study the sonocatalytic, photocatalytic and sonophotocatalytic decolorization as well as mineralization of Acid Blue 113 (AB113). Among the experimented nanocatalysts maximum degradation of AB113 was achieved in the presence Y³⁺-TiO₂ nanocatalysts. The decolorization of AB113 in the presence and absence of Y³⁺ loaded TiO₂ ensues the following order sonolysis < photocatalysis < sonocatalysis < sonophotocatalysis. The sonophotocatalytic decolorization of AB113 shows 1.4-fold (synergy index) enhanced rate when compared with the two corresponding individual advanced oxidation processes. The sonophotocatalytic mineralization shows that 65% of total organic carbon (TOC) can be removed from AB113 after the 5 h of continuous irradiation however the mineralization cannot be able to show the synergetic effect.