This paper, written by researchers from Liaoning University and others, discusses Preparation of Ce4+-doped BaZrO3 by hydrothermal method and application in dual-frequent sonocatalytic degradation of norfloxacin in aqueous solution. The paper is published in an important journal < Ultrasonics Sonochemistry >.IF：6.012.

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In this paper, the dual-frequent sonocatalytic degradation of norfloxacin (NOR), an antibiotic, caused by Ce4+- doped BaZrO3 is studied. The used Ce4+-doped BaZrO3 as a novel sonocatalyst with highly efficient and stable sonocatalytic activity is prepared via hydrothermal method. The prepared sample is characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS) and Fourier transform infrared spectra (FT-IR) in order to investigate the structure, morphology and chemical composition. The dual-frequent sonocatalytic activity of prepared Ce4+-doped BaZrO3 powder is evaluated through sonocatalytic degradation of norfloxacin (NOR) as a model organic pollutant. Some influencing factors such as single/dual-frequent ultrasonic frequent, cerium and zirconium molar proportions, ultrasonic irradiation time and used times are studied in detail by using UV–vis spectra. The generated reactive oxygen species (ROS) during the dual-frequent sonocatalytic degradation process of norfloxacin (NOR) are confirmed by using two different trapping agents. The holes (h+) and hydroxyl radicals (%OH) are identified and the holes plays a major role during the oxidation process. Finally, the possible mechanism for the dual-frequent sonocatalytic degradation of norfloxacin (NOR) caused by Ce4+-doped BaZrO3 is proposed. The experimental results show that the Ce4+-doped BaZrO3 displays a good sonocatalytic activity under dual-frequent ultrasonic irradiation. Under optimal conditions, the most of norfloxacin (NOR) can be removed under dual-frequent ultrasonic irradiation for 150 min.

In this work, the Ce4+-doped BaZrO3 as a new sonocatalyst was prepared by using hydrothermal method. And then, the sonocatalytic activity of Ce4+-doped BaZrO3 was evaluated through the sonocatalytic degradation of norfloxacin (NOR) in aqueous solution under dualfrequent ultrasonic irradiation. The prepared (0.048:0.952) Ce4+- doped BaZrO3 powder displays a good sonocatalytic activity during degradation of norfloxacin (NOR) under dual-frequent ultrasonic irradiation. The dual-frequent sonocatalytic degradation ratio can reach 69.81% for 10 mg/L initial concentration of norfloxacin (NOR), 1.00 g/ L (0.048:0.952) Ce4+-doped BaZrO3 addition amount, 150 min dualfrequent ultrasonic irradiation and 300W ultrasonic power. The experimental results indicate that, in the presence of Ce4+-doped BaZrO3, the sonocatalytic degradation ratio of norfloxacin (NOR) under dualfrequent ultrasonic irradiation is apparently better than that under single-frequent ultrasonic irradiation. The Ce4+ ion as dopant can slightly decrease the band gap of BaZrO3, which leads to a wide light response range of Ce4+-doped BaZrO3 powders. Also, the doped Ce4+ ion can efficiently restrain recombination of photogenerated electrons (e−) and holes (h+). The trapping agent experiments show that the dual-frequent sonocatalytic degradation is through a combined action of holes (h+) and hydroxyl radicals (%OH), but mainly caused by the holes (h+) oxidation.

The prepared Ce4+-doped BaZrO3 particles as sonocatalysts were characterized by X-ray powder diffractometer (XRD, D-8, Bruker-axs, Germany, Ni filtered Cu Kα radiation in the range of 2θ from 20° to 80°) and scanning electron microscopy (SEM, JEOL JSM-5610LV, Hitachi Corporation, Japan) to determine the crystalline phase and surface morphology. Energy dispersive X-ray analysis (EDX, JEOL JSM- 5610LV, Hitachi Corporation, Japan) and X-ray photoelectron spectroscopy (XPS, Escalab 250XI, Thermo, USA) were used to determine the element types and composition content of prepared Ce4+-doped BaZrO3. UV–vis diffuse reflectance spectra (DRS, UV-3600, SHIMADZU, Japan) was used measure the optical diffuse absorption spectra of prepared pure BaZrO3 and different molar proportions of Ce4+-doped BaZrO3. FTIR spectroscopy (FT-IR, Nicolet 5700, Beckman Coulter, USA) was used to further confirm the chemical composition of prepared Ce4+-doped BaZrO3. UV–vis spectrometer (Cary 50, Varian Company, USA) was used to inspect the sonocatalytic degradation processes of norfloxacin (NOR) in aqueous solution. Controllable dual-frequent combined Ultrasonics apparatus (XH-2008DE, Beijing Xianghu Science and Technology Development Company, China) and Serial-Ultrasonics apparatus (KQ-300, Kunshan Company, China) were adopted to irradiation the norfloxacin (NOR) solution, operating at ultrasonic frequent of 40 KHz, 25 KHz and 40 KHz+25 KHz, output power of 50W through numerical control adjust. Apparatus of ultrasonic irradiation was shown in Scheme 2.