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

• Sonophotocatalytic degradation of dye using rare earth doped TiO2.
• HRTEM shows that RE don’t have any influence on the crystal structure of TiO2.
• STEM-HAADF confirms that RE nanoclusters were present at the surface of the TiO2.
• Y3+-loaded TiO2 exhibits the maximum sonophotocatalytic degradation.
• 1.4-fold synergetic index was achieved for the sonophotocatalytic degradation.

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.