Sol-gel Synthesis of Boron Doped TiO2/hollow Glass Bubbles Composite Powders for Photocatalytic Degradation of Azophloxine

Background: B-TiO2 was supported on the surface of iM16K glass bubbles to achieve a suitable density for the B-TiO2/iM16K composite hollow spheres. Aeration or stirring in the wastewater can lead to thorough mixing of photocatalyst and wastewater. Solid-water separation is relatively easy because the materials can float on the water surface while stopping aeration or stirring. Methods: The iM16K glass bubbles were used to prepare boron-doped B-TiO2/iM16K composite hollow spheres through a sol-gel route. The materials were characterized by X-ray diffraction, scanning electron microscope, Fourier transforms infrared spectroscopy, UV-Visible diffuse reflectance spectrometry, and N2 adsorption-desorption techniques. The photocatalytic degradation of azophloxine on the composites was determined. Results: The bandgap energy of the B-TiO2/iM16K composite was slightly less than 3.0 eV when the calcination temperature was below 500°C. The sample calcined at 350°C had a BET surface area of 88.6 m²/g, while the value of the sample calcined at 800°C was 1.2 m²/g. The maximum photocatalytic degradation efficiency was obtained for the sample calcined at 450°C, and nearly all of the original azophloxine molecules were decomposed after 120 min of irradiation. Photocatalytic degradation efficiency after 30 min of irradiation was enhanced from 18.8% to 47.9% when the B-TiO2 dosage increased from 100 to 800 mg/L. Conclusion: Crystallization of anatase TiO2 was temperature-dependent, and the properties of BTiO2/ iM16K composite hollow spheres were affected by the phase composition of the boron-doped TiO2 layer. The change in calcination temperature can have a significant effect on the photocatalytic degradation of azophloxine. The production of hydroxyl radical depended on the photocatalytic activity of the B-TiO2/iM16K composite hollow spheres.