Propriétés réactives en post-décharge temporelle des décharges électriques glissantes dans l air humide (application à la dégradation de colorant azoïque et à la décontamination microbienne)

La décharge électrique glissante Glidarc dans l air humide est une source de plasma non thermique efficace dans l abattement de la pollution. Nous présentons dans ce mémoire l utilisation des propriétés réactives en post-décharge temporelle (c'est-à-dire après extinction de la décharge) du glidarc. Nous avons considéré dans un premier temps la dégradation en milieu acide du méthylorange, un colorant azoïque. Après exposition de la cible pendant des durées brèves à la décharge plasma, la dégradation en post-décharge temporelle s est effectuée suivant un processus global de 1er ordre avec conversion du colorant en N,N diméthyl-4- Nitroaniline comme produit majoritaire. D autre part, la post-décharge a été exploitée aussi pour inactiver les micro-organismes. Quatre micro-organismes dans les états planctonique et adhérent ont été considérés : Staphylococcus epidermidis et Leuconostoc mesenteroïdes comme bactéries à Gram positif, Hafnia alvei comme bactérie à Gram négatif et Saccharomyces cerevisiae comme modèle de levure. La post-décharge a été utilisée suivant deux voies : les cellules microbiennes étaient préalablement exposées la décharge pendant des durées brèves puis analysées en post-décharge ou alors elles étaient mises en contact avec une solution d eau activée par plasma . Dans tous les cas, on a obtenu des réductions significatives de la population microbienne suivant des cinétiques de 1er ordre. De tels résultas combinés avec la mise en évidence de la destruction par HNO2 et H2O2 suggèrent que les acides nitreux et peroxonitreux sont les principales espèces oxydantes impliquées dans le phénomène de post-décharge. Opérant en milieu acide, le rôle du cation nitrosonium NO+ a été également mis en évidence.The gliding electrical discharge "Glidarc" in the humid air is a source of non-thermal plasma at atmospheric pressure efficient for pollution abatement. We present in this thesis the benefit use of reactive properties in temporal post-discharge (i.e. after switch off the discharge) of glidarc. In the first step, we considered the degradation of acidic methyl orange, an azoic dye. After target exposure for short periods to the discharge plasma, a strong temporal post-discharge degradation of the dye giving N,N-dimethyl-4-Nitroaniline, as the major yellow intermediate product with a relevant overall first-order kinetics, was observed. On the other hand, post-discharge has also been used to inactivate micro-organisms. Four micro-organisms in planktonic and adherent forms were considered: Staphylococcus epidermidis and Leuconostoc mesenteroïdes as Gram-positive bacteria, Hafnia alvei as a gram-negative bacterium and Saccharomyces cerevisiae as a yeast model. The post-discharge was used in two ways: the microbial cells were previously exposed to discharge for short periods or they were inactivated by a solution of "plasma activated water . In all cases, significant reductions of the microbial populations were achieved with 1st order kinetic. Such results combined with the identification of the destruction by HNO2 and H2O2 suggest that nitrous and peroxonitrous acids are the main oxidizing species involved in the temporal post-discharge phenomenon. As the operation takes place under acidic medium, the role of nitrosonium NO+ was also highlighted.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Unraveling the sorption mechanisms of ciprofloxacin on the surface of zeolite 4A (001) in aqueous medium by DFT and MC approaches

The adsorption mechanism of ciprofloxacin (CIP) and its ionic form were investigated using density functional theory (DFT) and molecular dynamics (MD), with the goal of forecasting their adsorption behavior in terms of gap energy, global reactivity descriptors, Fukui functions, adsorption energies, and density of state on the surface of zeolite 4A (001). Quantum chemical parameters related to the adsorption process were calculated, as well as the overall reactivity. According to DFT calculations, the zwetterionic form CIP± are the most stable and reactive and have a greater power of electron transfer compared to the other species. Under aqueous conditions, zeolite can adsorb ciprofloxacin (CIP) and its ionic forms, as revealed by molecular dynamics simulation. Ciprofloxacin in the zwitterionic form (CIP±) were more efficiently adsorbed to the surface of zeolite 4A (001) than the cationic (CIP+), anionic (CIP−), and neutral(CIP) forms; through the evaluation of adsorption energy, probability distribution, interaction, and density of state. The results also demonstrated that the compounds studied were adsorbed via the process of chemical bonding, which was confirmed by the negative values of the interaction energy. Furthermore, the negative adsorption energy values suggest a significant adsorption of all compounds, with electrostatic interactions (physisorption), diffusion into the pores, and n-π bonds (chemisorption) on the zeolite surface. The increase in adsorption energies and the proximity of the molecules studied to the zeolite surface indicate the predominance of chemisorption, and the adsorption of ciprofloxacin was found to be an exothermic and spontaneous process. Molecular dynamics (MD) modeling was in agreement with the DFT results

FeOx-kaolinite catalysts prepared via a plasma-assisted hydrolytic precipitation approach for Fenton-like reaction

Iron oxides (FeOx) supported on clay minerals are efficient catalysts for the Fenton-like degradation of organic pollutants in water. This study explores a new preparation route for such catalysts by exploiting the use of gliding arc plasma at atmospheric pressure for the precipitation-deposition of FeOx particles onto kaolinite. The physicochemical properties of the synthesized catalysts and their activity in the degradation of the azoic dye Acid orange 7 (AO7) are herein evaluated. Results show that the catalysts consist of nanosized goethite fibres onto clay particles. The BET surface area of the catalysts was greater than that of kaolinite and depended on the Fe weight percentage in each catalyst. As a consequence, these materials were very active when tested in the catalytic degradation of AO7 (C0 = 25 mg L−1). Abatement efficiencies of 86% and 50% in terms of bleaching and degradation respectively were obtained after 120 min, in the presence of 0.2 g L−1 of catalyst with 9.4 wt% of Fe. Increasing the catalyst dosage enhanced the abatement efficiency. For the catalyst dosage of 3 g L−1, the bleaching and degradation efficiencies were 100% and 80% respectively after only 80 min. Moreover, the catalyst was still active in neutral and basic media, even if lower abatement efficiencies were obtained for neutral and basic dye solutions. On the other hand, the AO7 abatement efficiency of catalyst with 4.4 wt% of Fe was almost equal to that with 9.4 wt%, suggesting that 4.4% of iron in the catalyst is sufficient to transform in a reasonable time, all H2O2 into hydroxyl radicals. Finally, the recycling tests showed that the catalysts remain active even after three consecutive uses

Combined Effects of Long-Living Chemical Species during Microbial Inactivation Using Atmospheric Plasma-Treated Water▿

Electrical discharges in humid air at atmospheric pressure (nonthermal quenched plasma) generate long-lived chemical species in water that are efficient for microbial decontamination. The major role of nitrites was evidenced together with a synergistic effect of nitrates and H2O2 and matching acidification. Other possible active compounds are considered, e.g., peroxynitrous acid

Impact on disinfection efficiency of cell load and of planktonic/adherent/detached state: case of Hafnia alvei inactivation by Plasma Activated Water

This paper describes the effects of initial microbial concentration and planktonic/adherent/detached states on the efficiency of plasma-activated water. This disinfecting solution was obtained by treating distilled water with an atmospheric pressure plasma produced by gliding electric discharges in humid air. The inactivation kinetics of planktonic cells of Hafnia alvei (selected as a bacterial model) were found to be of the first order. They were influenced by the initial microbial concentration. Efficiency decreased when the initial viable population N0 increased, and the inactivation rate kmax was linearly modified as a function of Log10 (N0). This relation was used to compare planktonic, adherent, and detached cells independently from the level of population. Bacteria adhering to stainless steel and high-density polyethylene were also sensitive to treatment, but at a lower rate than their free-living counterparts. Moreover, cells detached from these solid substrates exhibited an inactivation rate lower than that of planktonic cells but similar to adherent bacteria. This strongly suggests the induction of a physiological modification to bacteria during the adhesion step, rendering adherent—and further detached—bacteria less susceptible to the treatment, when compared to planktonic bacteria

Plasma synthesis of various polymorphs of tungsten trioxide nanoparticles using gliding electric discharge in humid air: characterization and photocatalytic properties

A gliding electric arc (glidarc) discharge generates a low-temperature plasma at atmospheric pressure. When the discharge occurs in humid air as the feed gas, the chemistry of a glidarc plasma consists of in situ formation of HO° and NO° as the primary chemical species. Tungsten trioxide (WO3) nanoparticles were successfully prepared by exposure of a liquid precursor to glidarc plasma. The WO3 samples were calcined at three different temperatures (300 °C, 500 °C and 800 °C), resulting in different pure polymorphs: γ-WO3 (at 300 °C), β-WO3 (at 500 °C) and α-WO3 (at 800 °C) according to x-ray diffraction analysis. The identification of WO3 compounds was also confirmed by attenuated total reflection Fourier transform infrared spectroscopy analysis. Increase in the calcination temperature of WO3 induced a decrease in its specific surface area according to Brunauer–Emmett–Teller nitrogen physisorption analysis. The UV-visible results showed that the absorption bands of plasma-WO3 samples were more intense than those of WO3 samples obtained by a precipitation route, a classical method used for comparison. Consequently, this parameter can improve the photocatalytic properties of WO3 under visible light. The photodegradation (in sunlight conditions) of gentian violet, chosen as a model pollutant, confirmed the photocatalytic properties of plasma-WO3 samples. This novel synthesis method has great potential to improve the efficiency of advanced tungsten trioxide-based functional material preparation, as well as in pollution-reducing and energy-saving tungsten extractive metallurgy

Evidence of Temporal Postdischarge Decontamination of Bacteria by Gliding Electric Discharges: Application to Hafnia alvei▿

This study aimed to characterize the bacterium-destroying properties of a gliding arc plasma device during electric discharges and also under temporal postdischarge conditions (i.e., when the discharge was switched off). This phenomenon was reported for the first time in the literature in the case of the plasma destruction of microorganisms. When cells of a model bacterium, Hafnia alvei, were exposed to electric discharges, followed or not followed by temporal postdischarges, the survival curves exhibited a shoulder and then log-linear decay. These destruction kinetics were modeled using GinaFiT, a freeware tool to assess microbial survival curves, and adjustment parameters were determined. The efficiency of postdischarge treatments was clearly affected by the discharge time (t*); both the shoulder length and the inactivation rate kmax were linearly modified as a function of t*. Nevertheless, all conditions tested (t* ranging from 2 to 5 min) made it possible to achieve an abatement of at least 7 decimal logarithm units. Postdischarge treatment was also efficient against bacteria not subjected to direct discharge, and the disinfecting properties of “plasma-activated water” were dependent on the treatment time for the solution. Water treated with plasma for 2 min achieved a 3.7-decimal-logarithm-unit reduction in 20 min after application to cells, and abatement greater than 7 decimal logarithm units resulted from the same contact time with water activated with plasma for 10 min. These disinfecting properties were maintained during storage of activated water for 30 min. After that, they declined as the storage time increased

Effect of cation insertion on the stability of gliding arc plasma-precipitated mesoporous MnO2 dye bleaching catalysts

α-MnO2 and γ-MnO2 polymorphs were, respectively, obtained from the plasma precipitation of KMnO4 and Mn(CH3COO)3⋅2H2O precursors. The obtained powders were calcined at 150 °C, 210 °C and 400 °C, and characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), nitrogen physisorption and Scanning electron microscopy (SEM). As a result, the calcination does not significantly affect textural properties and crystalline structure of the α-MnO2, while γ-MnO2 is transformed into β-MnO2 for temperatures above 400 °C. The thermal stability α-MnO2 is due to the K+ ions insertion in its 4.6 Å × 4.6 Å tunnels and corroborated the catalytic performance of 100, 98, 98 and 97% compared to 71, 54, 52 and 48% for γ-MnO2 after four successive reuse cycles on Tartrazine Yellow dye. The insertion of cationic species (K+, Na+, Mg2+) into the structure of MnO2 reinforces its crystalline structure and promotes the formation of powerful oxidizing species through oxygen vacant sites

Microbial inactivation using plasma-activated water obtained by gliding electric discharges

Aim: To evaluate the microbial disinfection efficacy of a plasmachemical solu-tion obtained by the activation of water with gliding electric discharges.Methods and Results: Distilled water was activated for 5 min by a nonthermalquenched plasma of the glidarc type operating in humid air and at atmosphericpressure. The plasma-activated water (PAW) was then used to treat planktonicand adherent cells of Staphylococcus epidermidis, Leuconostoc mesenteroides (asmodels of Gram-positive bacteria), Hafnia alvei (a Gram-negative bacteria) andSaccharomyces cerevisiae (as a yeast model). The treatments were less efficienton adherent cells than on planktonic cells in the case of bacteria, but not ofS. cerevisiae. Inactivation was more effective for bacteria than for the yeast.Conclusions: Significant reductions in microbial populations were achieved inall cases, demonstrating the effectiveness of this new approach to treat conta-minated media.Significance and Impact of the Study: PAW is a promising solution withpotential application to the decontamination of equipment and surfaces

Chemical reactivity of discharges and temporal post-discharges in plasma treatment of aqueous media: examples of gliding discharge treated solutions

Environmental applications of electric discharges are being considered increasingly more often: they imply the chemical properties of the activated species generated in and by the discharge. An overview of the resulting chemical effects is presented, based on rationalized classification, i.e., acid-base effects, oxidizing properties, complex forming reactions, and radical reactions. The gliding discharge is considered to be a specifically suitable plasma source for the treatment of liquids for pollutant abatement in the scope of sustainable environment, and this justifies an overview of the chemical properties. Special emphasis is devoted to temporal post-discharge reactions (TPDRs), which occur when the target is no longer exposed to the plasma source, and several typical examples are detailed. These recently evidenced TPDRs seem to present some general character. They are the key parameters to estimating the efficiency of a discharge treatment; they also have major technical and economical importance for the application of the plasma treatment to pollutant and/or micro-organism abatement at atmospheric pressure and quasi-ambient temperature