Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

• Six metal-embedded TiO2 photocatalysts were synthesized using a sonochemical process.
• Most metal-embedded TiO2 showed improved activity for benzene and toluene degradation.
• There was an optimal set of ultrasonic treatment conditions for metal-embedded TiO2.
• Different metal dopants provided different photocatalytic performances.

Titania (TiO2) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO2 (metal–TiO2) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV–visible spectroscopy, and nitrogen adsorption–desorption. Except for Co–TiO2, the metal–TiO2 photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg–TiO2 sample, followed by, in order, the Ag–TiO2, Ce–TiO2, Fe–TiO2, Mn–TiO2, unmodified TiO2, and Co–TiO2 samples. Although Mg–TiO2 showed the least redshift in its light absorption and the highest electron–hole recombination rate among the metal–TiO2 photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg–TiO2 improved as ultrasound treatment amplitude increased from 20 to 37 μm, then decreased gradually as amplitude was further increased to 49 μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60 min, then decreased gradually as amplitude was further increased to 90 min. Overall, this process could be utilized to prepare metal–TiO2 photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.