Nonthermal plasma assisted photocatalytic oxidation of dilute benzene

Oxidative decomposition of low concentrations (50-1000 ppm) of diluted benzene in air was carried out in a nonthermal plasma (NTP) dielectric barrier discharge (DBD) reactor with the inner electrode made up of stainless steel fibres (SMF) modified with transition metal oxides in such a way to integrate the catalyst in discharge zone. Typical results indicate the better performance of MnOx and TiO2/MnOx modified systems, which may be attributed to the in situ decomposition of ozone on the surface of MnOx that may lead to the formation of atomic oxygen; whereas ultraviolet light induced photocatalytic oxidation may be taking place with TiO2 modified systems. Water vapour improved the selectivity to total oxidatio

Enhanced seed germination and plant growth by atmospheric pressure cold air plasma: combined effect of seed and water treatment

International audienceThe combined effect of non-thermal plasma treatment of water and seeds on the rate of germination and plants growth of radish (Raphanus sativus), tomato (Solanum lycopersicum), and sweet pepper (Capsicum annum) have been investigated using dielectric barrier discharges in air under atmospheric pressure and room temperature. A cylindrical double dielectric barrier discharge reactor is used for water activation and a plate-to-plate double DBD reactor is employed for seed treatment. The activation of water, for 15 and 30 min, lead to acidic solutions (pH  3) with moderate concentrations of nitrate (NO3-) and hydrogen peroxide (H2O2). Plasma activated water (PAW) has shown a significant impact on germination as well as plant growth for the three types of seeds used. Interestingly, the positive effect, in seed germination and seedling growth, has been observed when the PAW and plasma-treated seeds (10 and 20 min) were combined. In one hand, when the seeds were (tomato and pepper) exposed to 10 min plasma and watered with PAW-15 for first 9 days followed by tap water for 51 days, the stem length is increased about 60% as compared to control sample. On the second hand, for longer exposures of seeds and water to plasma discharges, a negative effect is observed. For instance, plasma-treated seeds watered with PAW-30, the plant growth and vitality were decreased as compared to control sample. These results revealed that the developed cold plasma reactors could be used to significantly improve the seed germination as well as plant growth, nevertheless, the plasma treatment time has to be optimized for each seeds

DBD plasma reactor for oxidative decomposition of chlorobenzene

Oxidative decomposition of chlorobenzene diluted in air was carried out in a dielectric barrier discharge reactor. In order to understand the role of the ground electrode, various reactor configurations were tested. Among silver paste, copper wire and aluminum foil tested as the outer electrodes, typical results indicated the best performance of silver paste, probably due to uniform distribution of microdischarges. Likewise, low flow rates gave better conversion and selectivity to gaseous products

Catalytic nonthermal plasma reactor for the abatement of low concentrations of isopropanol

Oxidative decomposition of a model volatile organic compound (isopropanol, IP) has been carried out in a catalytic dielectric barrier discharge (DBD) reactor, where modified sintered metal fiber (SMF) filter was used as the inner electrode. The SMF was modified with Mn and Co oxides by impregnation, followed by calcination and the performance of the DBD reactor was tested for the oxidation of IP in the specific input energy range 160-720J/l by varying the high voltage and frequency. It has been observed that SMF modification by MnOx and CoOx not only improved the conversion of isopropanol, but also increased the selectivity towards total oxidation. MnOx modification showed better performance than CoOx, which may be attributed to the formation of atomic oxygen by in situ decomposition of ozone. It has been demonstrated that with MnOx/SMF it is possible to completely oxidize 100ppm of isopropanol at SIE<200J/l

NO2 adsorption mechanism on TiO2: An in-situ transmission infrared spectroscopy study

SSCI-VIDE+ING+DBIInternational audienceThe adsorption of NO2 on oxidized TiO2 surface, under dark condition at 296 K, has been investigated by in-situ transmission Fourier Transform Infrared Spectroscopy (trans-FTIR) as a function of time. It enabled the determination of detailed NO2 reactive adsorption mechanisms on TiO2. It was evidenced that, as soon as NO2 molecules adsorb on TiO2 surface it dimerize to adsorbed N2O4 species. The strongly adsorbed N2O4 undergoes intramolecular disproportionation reaction and produces: (i) weakly adsorbed monodentate nitrate (m-NO3−) species and, (ii) highly reactive NO+ and/or N2O3 species on Ti4+ sites and O2− sites, respectively. The NO+ species reacts with surface lattice oxygen (O2−) and produces more stable NO2− on Ti4+ sites. Then, the NO2− undergoes intermolecular disproportionation reaction with another strongly adsorbed N2O4 molecule and produces strongly adsorbed bidentate nitrate (b-NO3−) species on Ti4+ sites and releases NO in the gas phase. It was also noticed that, as adsorption time increases, the weakly adsorbed m-NO3− species are converted into strongly adsorbed b-NO3− species. The intramolecular disproportionation reaction rate depends on NO2 partial pressure, whereas the intermolecular disproportionation reaction rate depends on the coverage of NO2− species and the number of available Ti4+ sites. This mechanism is assessed for different NO2 partial pressures ranging from 25 to 100 Pa. This study reveals that the configuration and the amount of the N-containing species on activated TiO2 surface depend on the NO2 concentration and the contact time

The 40 m 3 Innovative experimental Room for INdoor Air studies (IRINA): Development and validations

International audienc