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

Abstract

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 quite 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 transform infrared spectroscopy, UV-Visible diffuse reflectance spectrometry, and N2 adsorption-desorption techniques. 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 500oC. The sample calcined at 350oC had a BET surface area of 88.6 m2 /g, while the value of the sample calcined at 800oC was 1.2 m2 /g. The maximum photocatalytic degradation efficiency was obtained for the sample calcined at 450oC, 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 B-TiO2 dosage increased from 100 to 800 mg/L. Conclusion: Crystallization of anatase TiO2 was temperature dependent, and the properties of B-TiO2/iM16K composite hollow spheres were affected by phase composition of the boron-doped TiO2 layer. The change in calcination temperature can have significant effect on photocatalytic degradation of azophloxine. The production of hydroxyl radical depended on photocatalytic activity of the B-TiO2/iM16K composite hollow spheres.