Ammonia and methane oxidation on TiO₂ supported on glass fiber mesh under artificial solar irradiation

In this work, we present the application of solar photocatalysis for air purification including toxic substances such as ammonia and methane normally related to emissions from agriculture (e.g., poultry and cattle farms), landfills, etc. The study was done in three different laboratory and semi-pilot scale reactors: annular reactor (AR), mini-photocatalytic wind tunnel (MPWT), and photocatalytic wind tunnel (PWT). Reactors present a physical model for estimation of air-borne pollutant degradation over TiO₂-based photocatalytic layer in respect to optimal operating conditions (relative humidity, air/gas flow, and feed concentration). All studies were performed under artificial solar irradiation with different portions of UVB and UVA light. The application of solar photocatalysis for air purification was evaluated based on thorough monitoring of pollutants in inlet and outlet streams. The kinetic study resulted with intrinsic reaction rate constants: k_p,int,NH3 = (3.05 ± 0.04) × 10^-3 cm^4.5 mW^-0.5 g^-1 min^-1 and k_p,int,CH4 = (1.81 ± 0.02) × 10^-2 cm^4.5 mW^-0.5 g^-1 min^-1, calculated using axial dispersion model including mass transfer considerations and first-order reaction rate kinetics with photon absorption effects. The results of photocatalytic oxidation of NH₃ and CH₄ confirmed continuous reduction of pollutant content in the air stream due to the oxidation of NH₃ to N₂ and CH₄ to CO and CO₂, respectively. The application of solar photocatalysis in outdoor air protection is still a pioneering work in the field, and the results obtained in this work represent a good basis for sizing large-scale devices and applying them to prevent further environmental pollution. In the current study, a TiO₂ P25 supported on a glass fiber mesh was prepared from commercially available materials. The system designed in this way is easy to perform, operate, and relatively inexpensive.