The investigation of sonocatalytic activity of Er3+:YAlO3/TiO2-ZnO composite in azo dyes degradation

In this work, the emphasis was mainly placed on investigating the sonocatalytic activity of TiO2-ZnO mixed with Er3+:YAlO3, namely, Er3+:YAlO3/TiO2-ZnO composite. It is able to utilize the sonoluminescence light to improve the sonocatalytic degradation of organic dyes. The Er3+:YAlO3 as up-conversion luminescence agent was synthesized by sol–gel and auto-combustion method, and then Er3+:YAlO3/TiO2-ZnO composite as sonocatalyst were prepared by ultrasonic dispersion and liquids boil method. The prepared up-conversion luminescence agent and composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Acid Red B dye was selected to examine the sonocatalytic activity of Er3+:YAlO3/TiO2-ZnO composite. The degradation reaction processes were monitored by UV–vis spectrophotometer and ion chromatogram. The influences on the activity of the Er3+:YAlO3/TiO2-ZnO such as Ti/Zn molar ratio, heat-treated temperature and heat-treated time were studied. The results showed that the Er3+:YAlO3/TiO2-ZnO composite exhibited a significantly high sonocatalytic activity compared with other catalysts in the degradation of Acid Red B. And the sonocatalyst with 1:1 Ti/Zn molar ratio heat-treated at 550 °C for 60 min showed the highest sonocatalytic activity. At last, the experiment also indicated that it has a good sonocatalytic activity to degrade other organic dyes.

Research highlights
► Er3+:YAlO3 was combined with TiO2-ZnO for effectively utilizing sonoluminescence.
► A novel sonocatalyst Er3+:YAlO3/TiO2-ZnO was synthesized successfully.
► The Er3+:YAlO3/TiO2-ZnO irradiated by ultrasound was used to degrade organic dyes.
► The activity of TiO2 is effectively enhanced by Er3+:YAlO3 and mixed ZnO.