Improvement of sonocatalytic activity of TiO2 by using Yb, N and F-doped Er3+:Y3Al5O12 for degradation of organic dyes

In this study, several up-conversion luminescence agents (Er3+:Y3Al5O12, Er3+:Yb0.2Y2.79Al5O12, Er3+:Yb0.2Y2.79Al5N0.01O11.99, Er3+:Yb0.2Y2.79Al5F0.01O11.99 and Er3+:Yb0.2Y2.79Al5N0.01F0.01O11.98) were synthesized using sol–gel method. And then, the corresponding sonocatalyst (Er3+:Y3Al5O12/TiO2, Er3+:Yb0.2Y2.79Al5O12/TiO2, Er3+:Yb0.2Y2.79Al5N0.01O11.99/TiO2, Er3+:Yb0.2Y2.79Al5F0.01O11.99/TiO2 and Er3+:Yb0.2Y2.79Al5N0.01F0.01O11.98/TiO2 coated composites) were prepared by sol–gel coating process. The synthesized up-conversion luminescence agents and their coated composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). And that, the sonocatalytic activities were detected through the degradation of Azo Fuchsine (AF) dye in aqueous solution by UV–vis spectroscopy. Some key influences such as heat-treated temperature and heat-treated time on the sonocatalytic activity of Er3+:YbaY2.99−aNxFyAl5O12−x−y/TiO2 coated composite, as well as ultrasonic irradiation time and initial dye concentration on the sonocatalytic degradation were studied. The results showed that the doping of Yb, N and F into Er3+:Y3Al5O12/TiO2 significantly enhanced the sonocatalytic activity of Er3+:Y3Al5O12/TiO2 coated composite in the degradation of organic dyes. Particularly, Er3+:Yb0.2Y2.79Al5N0.01F0.01O11.98/TiO2 coated composites with 3:7 M ratio heat-treated at 550 °C for 60 min showed the highest sonocatalytic activity. At last, the experiments also indicated that the Er3+:Yb0.2Y2.79Al5N0.01F0.01O11.98/TiO2 coated composites has a good sonocatalytic activity to degrade other organic dyes under ultrasonic irradiation.