Gaseous ethylbenzene removal by photocatalytic TiO2 nanoparticles immobilized on glass fiber tissue under real conditions: evaluation of reactive oxygen species contribution to the photocatalytic process.

Photocatalytic oxidation (PCO) using a TiO2 catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a lab-scale continuous reactor is used to investigate the photocatalytic performance toward ethylbenzene (EB) vapor removal over TiO2 nanoparticles immobilized on glass fiber tissue. The role of the reactive species in the removal of EB and the degradation pathway were studied. Firstly, the effect of key operating parameters such as EB concentration (13, 26, 60 mg/m3), relative humidity levels (From 5 to 80%), gas carrier composition (dry air + EB, O2 + EB and N2 + EB) and ultraviolet (UV) radiation wavelength (UV-A 365 nm, UV-C 254 nm) were explored. Then, using superoxide dismutase and tert-butanol as trapping agents, the real contribution of superoxide radical anion (O2.-) and hydroxyl radicals (OH.) to EB removal was quantified. The results show that (i) small water vapor content enhances the EB degradation; (ii) the reaction atmosphere plays an important role in the photocatalytic process; and (iii) oxygen atmosphere/UV-C radiation shows the highest EB degradation percentage. The use of radical scavengers confirms the major contribution of the hydroxyl radical to the photocatalytic mechanism with 75% versus 25% for superoxide radical anion.