Heterogeneous Photocatalytic Oxidation of Pollutants in Air on TiO2 Particles

A semiempirical method has been developed for analyzing the mechanism of heterogeneous reactions based on the Langmuir–Hinshelwood kinetic model modified using the first- order double-exponential decay approach. The method proved useful for describing the kinetics of photocatalytic oxidation (PCO) on TiO2 particles in air for a wide range of substances: ketones, organophosphorus compounds, alkyl sulfides, and chlorinated hydrocarbons. The range of substances can certainly be considerably expanded. An equation of implicit function was derived that describes the kinetics of heterogeneous PCO of the zeroth, first, and intermediate (between the zeroth and first) orders. Approximation of the experimental time dependence of concentration using this equation makes it possible to determine the reaction order including the intermediate one, the characteristic decay time of the substance, and the fraction of the exponential components in the kinetic equation. This semiempirical method was used for processing both the original experimental data obtained in the present study and the literature data. The time dependences of trichloroethylene (TCE) concentrations in a closed space during the heterogeneous PCO on TiO2 aerosol catalyst particles were studied using a specially designed unit. The catalytic activity increased with the aerosol concentration Cas: at Cas = 10.23, 14.17, and 19.85 g/m3, 90% purification of air from TCE was reached in 8.5, 5.0, and 1.5 min, respectively.