Nanoglued Titanium Dioxide Aerogels for Photocatalysis

Abstract

A titania–silica binary aerogel, composed of titanium dioxide thermally processed into its anatase form and "nanoglued" to a glass surface using an about-to-gel silica sol, was prepared to test for photocatalytic efficiency. The titanium dioxide core of this binary aerogel was characterized as being approximately 100% anatase through X-ray diffraction analysis, an important conclusion in that the anatase crystalline form has been shown to be more efficient as a photocatalyst than other morphologic forms of titanium dioxide. The surface areas for the four titania aerogel catalysts prepared ranged from 91.47–130.70 m²/g, and the catalysts had the highest density of pore radii of between 20–30 Å. The BET surface areas found were approximately twice as large as that of the current research standard, Degussa P-25. The increase in surface areas allows for more decontamination to take place based on Langmuir–Hinshelwood kinetics. The catalysts were tested in water containing Escherichia coli at a concentration of 1 × 10⁸ cfu/mL. Each of the catalysts showed decontamination of the wastewater, with the most efficient catalyst being the catalyst with the largest surface area. This finding agrees with the Langmuir-Hinshelwood assumption that larger surface area leads to more contaminant adsorption, and therefore greater destruction. The first-order rate constants for the photocatalytic testing ranged from 0.0068–0.0123 min⁻¹ compared to approximately 0.0063 min⁻¹ for the blanks. Statistical analysis using multivariate linear regression suggests that the mechanisms of destruction using "nanoglued" composite aerogels are affected by the presence of TiO₂ and catalyst surface area.