Effect of key parameters on the photocatalytic oxidation of toluene at low concentrations in air under 254 + 185 nm - UV irradiation

NATALIA QUICI; MARÍA L. VERA; HYEOK CHOI; GIANLUCA LI PUMA; DIONYSIOS D. DIONYSIOU; MARTA I. LITTER; HUGO DESTAILLATS

Cyprus

Conferencia; EAAOP2: 2nd European Conference on Environmental Applications of Advanced Oxidation Processes; 2009

Technical University of Crete, University of Cyprus, Aristotle University of Thessaloniki

The effect of key experimental parameters on the removal of toluene at low concentrations (10 and 500 ppbv) under 254 + 185 nm irradiation was investigated using a benchtop photocatalytic flow reactor with TiO2-coated Raschig rings. In the studied conditions, toluene removal efficiencies were between 30 and 90%. For each airflow rate, the conversion of toluene was significantly higher when the reactor length was 10 cm, as compared with 5 cm; however, only marginal increases in conversions were achieved in the two reactor lengths at equal residence time and different concentration of toluene, suggesting that that the reactor is effectively behaving as an ideal reactor. Relative humidity was varied, the fastest reaction rate being observed at moderately low humidity conditions (10% RH). Formaldehyde was formed as a partial oxidation byproduct, and the higher formaldehyde molar yields were observed at low residence time (t, 240 ms) and moderate humidity conditions (10 and 33%). Toluene removal efficiency increased with the TiO2 thickness until a maximum value of 500 nm, beyond which the removal efficiency decreased. This should be attributed to limitations on the rates of toluene decomposition imposed by radiation transport through the film and/or internal diffusion resistances that can take place within the porous photocatalytic films.