Photocatalytic Degradation Of Gaseous Toluene Research Articles

Mechanistic study and mutagenicity assessment of intermediates in photocatalytic degradation of gaseous toluene

Photocatalytic oxidation is a promising technique for the degradation of volatile organic compounds. However, it is necessary to clarify the genotoxicity mutagenic potential of intermediates formed during photocatalytic degradation. A gas–solid TiO 2 thin film reactor was fabricated to degrade toluene under UV irradiation. The results showed that the degradation efficiencies of toluene at a concentration of about 1500 μg L −1 reached almost 100% within 120 min of illumination. The intermediates produced during the photocatalytic degradation were identified by using gas chromatography–mass spectroscopy. Benzene was the only by-product identified in the gas phase, while small amounts of benzaldehyde and benzoic acid were detected at the TiO 2 surface. Species such as benzene and CO 2 should derive from the photo-decarboxylation of benzoic acid, produced by further oxidation of benzaldehyde. Neither the original toluene nor the gaseous intermediates produced at different times presented mutagenic activity to strains TA98 and TA100 in the presence or absence of the S9 mixture at the tested doses by using Ames assay. All of the results indicated that the effluent gas of toluene treated by photocatalysis will not cause mutagenic toxicity to humans or other organisms.

초음파 발생 미스트를 이용한 TiO2 광촉매 시스템에서의 가스상 톨루엔 제거

Feasibility study of using <TEX>$Ti0_2$</TEX> mist generated by ultrasonic atomization for photocatalytic degradation of gaseous toluene was attempted in this study. For this, the photocatalytic reactor consisting of mist generator and photo-reactor was designed. Most of experimental results showed that steady state reached about 30 minutes after the start of experiments. The effects of <TEX>$Ti0_2$</TEX> concentration, toluene concentration, and UV wavelength on toluene removal ratio were investigated. It was found that the highest removal efficiency was obtained when <TEX>$Ti0_2$</TEX> concentration was 0.6 g/L in slurry. At this condition, it was found that the toluene removal efficiency increased as toluene concentration in feed decreased. In order to investigate the effect of UV wavelength, experiments were carried out using three UV lamps with different UV wavelength. The results showed that the highest removal efficiency was achieved when the lamp with the shortest wavelength were employed.

Photocatalytic degradation of gaseous toluene in an ultrasonic mist containing TiO2 particles

Abstract Photocatalytic degradation of toluene gas in a mist formed by ultrasonic atomization of slurried TiO 2 was studied under various conditions. Upon irradiation at 365 nm, toluene was decomposed and mineralized by photocatalytic reaction on the mist surface or inside it. The toluene removal ratio increased as the amount of TiO 2 in the slurry was increased. Under UV 254+185 irradiation, the mineralization ratio was higher than at 365 nm. We propose that under UV 254+185 irradiation, toluene was immediately converted to water-soluble intermediates by direct photolysis and O 3 oxidation in the gas phase and that these intermediates were captured in the mist and photocatalytically mineralized to CO and CO 2 . This paper indicates a new effective utilization of ultrasonic mist and TiO 2 photocatalyst.

Photochemical and photocatalytic degradation of gaseous toluene using short-wavelength UV irradiation with TiO 2 catalyst: comparison of three UV sources

The feasibility of the use of short-wavelength UV (254 + 185 nm) irradiation and TiO 2 catalyst for photodegradation of gaseous toluene was evaluated. It was clear that the use of TiO 2 under 254 + 185 nm light irradiation significantly enhanced the photodegradation of toluene relative to UV alone, owed to the combined effect of photochemical oxidation in the gas phase and photocatalytic oxidation on TiO 2. The photodegradation with 254 + 185 nm light irradiation was compared with other UV wavelengths (365 nm (black light blue lamp) and 254 nm (germicidal UV lamp)). The highest conversion and mineralization were obtained with the 254 + 185 nm light. Moreover, high conversions were achieved even at high initial concentrations of toluene. Catalyst deactivation was also prevented with the 254 + 185 nm light. Regeneration experiments with the deactivated catalyst under different conditions revealed that reactive oxygen species played an important role in preventing catalyst deactivation by decomposing effectively the less reactive carbon deposits on the TiO 2 catalyst. Simultaneous elimination of photogenerated excess ozone and residual organic compounds was accomplished by using a MnO 2 ozone-decomposition catalyst to form reactive species for destruction of the organic compounds.