Kinetic Study for Photocatalytic Oxidation of Elemental Mercury on a SiO 2 –TiO 2 Nanocomposite

Abstract

The kinetics of photocatalytic oxidation of elemental mercury (Hg⁰) on a SiO₂–TiO₂ nanocomposite with UV irradiation was studied in a fix-bed reactor under both dry and humid conditions. The experimental data were analyzed using a Langmuir-Hinshelwood (L-H) model. The reaction rate was successfully expressed using the model, indicating the L-H nature of Hg⁰ photocatalytic oxidation on the SiO₂–TiO₂ nanocomposite. The L-H model prediction suggests a great potential of the SiO₂–TiO₂ nanocomposite for Hg⁰ removal from high concentration emission sources. On the other hand, the rate of photocatalytic Hg⁰ oxidation was found to be significantly inhibited by the presence of water vapor. This may be explained by the competitive adsorption of water vapor on the TiO₂ surface, which results in the reduction of available adsorption sites for Hg⁰.