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.

Continuous air purification by front flow photocatalytic reactor: Modelling of the influence of mass transfer step under simulated real conditions.

In this work, a solution for the treatment of toxic gases based on a photocatalytic process using TiO2 coated on a cellulosic support, has been investigated. Here, cyclohexane was chosen as the reference for testing its removal efficiency via a continuous front flow reactor as type A anti-gas filters. The photocatalytic support was firstly characterized by EDX, to confirm its elemental composition. Then, the experiments were carried out, starting with a batch reactor in order to evaluate the degradation efficiency of the photocatalytic media, as well as the monitoring of the photocatalytic process which allowed the establishing of a carbon mass balance corresponding to the stoichiometric number of our target pollutant. The transition to a continuous treatment with a front flow reactor aims to highlight the influence of the input concentration (0.29-1.78 mM m-3) under different flow rates (12, 18 and 36 L min-1). The relative humidity effect was also investigated (from 5 to 90% of humidity) where an optimum rate was obtained around 35-45%. In addition, the mineralization rate was monitored. The major rates obtained were for a cyclohexane input concentration of 0.29 mM m-3 in wet condition (38%) at an air flow rate of 18 L min-1, where the CO2 selectivity reached 77% for an abatement of 62%. In order to understand the limiting steps of the photocatalytic process, a model considering the reactor geometry and the hydraulic flow was developed. The obtained results showed that the mass transfer must be considered in the photocatalytic process for a continuous treatment. The Langmuir-Hinshelwood bimolecular model was also developed to represent the influence of the humidity.