Florence Benoit-Marquié

VOC photodegradation at the gas–solid interface of a TiO2 photocatalyst: Part I: 1-butanol and 1-butylamine

Abstract The gas–solid heterogeneous photocatalytic oxidation of 1-butanol and 1-butylamine in air was investigated using supported TiO2 as a catalyst. The supported catalyst was prepared using a sol–gel method and irradiated employing two different light sources, a medium pressure mercury lamp or a xenon-chloride excimer lamp. The experimental set-up was especially designed for generating a gas stream containing stable and defined concentrations of the model pollutants. The gas stream at the reactor exit was analyzed on line by gas chromatography and the structures of the intermediates were established by gas chromatography coupled with mass spectrometry. Six major intermediates (butanal, butanoic acid, 1-propanol, propanal, ethanol and ethanal) were identified in the case of the photocatalytic degradation of 1-butanol. 1-Butylamine was less efficiently adsorbed on the catalyst and its degradation was slower. Three intermediates could be identified in this case (N-butylidene-1-butylamine, N-ethylidene-1-butylamine and N–butylformamide). Based on these results, a degradation mechanism is proposed for both compounds. Mineralization could be achieved under various conditions of concentrations and flow rates and was confirmed by infrared spectroscopy.

Photocatalytic degradation of 2,4-dihydroxybenzoic acid in water: efficiency optimization and mechanistic investigations

Abstract The experimental design and response surface methodologies have been applied to the investigation of the TiO 2 -photocatalytic degradation of 2,4-dihydroxybenzoic acid (DHBA) in aqueous solutions. It has been shown that a quadratic polynomial model may be used to assess adequately the efficiency of the photocatalytic degradation as a function of DHBA and TiO 2 concentrations. Moreover, the study of response surfaces leads to optimal conditions for investigating the catalyst efficiency. A degradation mechanism involving the cleavage of the DHBA aromatic ring at an early stage of the reaction is proposed. Such a mechanism accounts for the absence of any aromatic intermediate in the degradation process.

Hydrogen peroxide evolution during V-UV photolysis of water

Hydrogen peroxide evolution during the vacuum-ultraviolet (V-UV, 172 nm) photolysis of water is considerably affected by the presence of oxalic acid (employed as a model water pollutant) and striking differences are observed in the absence and in the presence of dioxygen.

Coupling of Adsorption on Zeolite and V-UV Irradiation for the Treatment of VOC Containing Air Streams: Effect of TiO2 on the VOC Degradation Efficiency

Abstract We have investigated the efficiency of the coupling of adsorption on a zeolite material (DAY) and UV or V-UV irradiation for the treatment of VOC containing air streams. We have compared the efficiency of photodegradation of two pollutants (1-butanol and toluene) in the absence and in the presence of TiO2 deposited on DAY (DAY/TiO2). Irradiation was performed with two different excimer lamps emitting in the V-UV at 172 nm and in the UV at 308 nm. The gaseous effluent was analyzed on-line at the exit of the photochemical reactor by GC and FTIR. The adsorbents (DAY and DAY/TiO2) were analyzed before and after irradiation by solid state NMR, and the residual organic products remaining on the solids by GC-MS after extraction. The results show that the coupling of adsorption on DAY/TiO2 and V-UVirradiation is highly efficient both for VOC mineralization and adsorbent regeneration. This efficiency results from the synergy between the important contribution of VUV photolysis to the oxidative degradation of the VOC and the photocatalytic effect of TiO2 under V-UV irradiation at the DAY/TiO2 surface, preventing adsorbent fouling as observed in the absence of TiO2. The contribution of TiO2 was particularly remarkable in the case of toluene.