Jean-Louis Brisset

Density and Rotational Temperature Measurements of the OH° and NO° Radicals Produced by a Gliding Arc in Humid Air

The predominant reactive species of a gliding arc in humid air, 50% relative humidity (50% RH), are identified from emission spectroscopy measurements to understand and explain the glidarc plasma interaction with aqueous solutions. The rotational temperatures of the main particles (i.e., the OH° and NO° radicals) are derived from comparing experimental and synthetic spectra at various locations in the plasma stream with different airflow rates. The temperatures decrease rather moderately downstream from the starting section of the arc (the neck) and they rather steeply increase with increasing the mass flow rate. Density measurements are also performed for the same experimental conditions to determine their evolution in the non-equilibrium zone. Although they are quasi-constant along the plasma jet axis, the OH° density is much higher than the NO° one. The chemical processes, which may lead to a constant regeneration of these prevailing reactive particles in a humid air gliding arc plasma, are also discussed. The complex composition of the plasma gas makes other chemical processes fairly possible, which may result in abundant species depending on the compound proportions.

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

ABSTRACT 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.

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

Aim:  To evaluate the microbial disinfection efficacy of a plasmachemical solution obtained by the activation of water with gliding electric discharges.

Peroxynitrite: A Re-examination of the Chemical Properties of Non-thermal Discharges Burning in Air Over Aqueous Solutions

The main compounds of non-thermal plasmas generated by a discharge in humid air at atmospheric pressure are re-examined to explain the twin chemical properties of discharges over aqueous waste solutions, i.e. the acid and oxidizing effects. The acid effects are attributed to transient nitrous and peroxynitrous acids and to stable nitric acid. The matching oxidizing power of the discharge species onto solutes is due to water soluble H2O2 provided by the dimer formation of °OH and also to peroxynitrous acid ONOOH and its salt which are involved in the oxidation process of nitrous to nitric acid.

Disposal of spent tributylphosphate by gliding arc plasma.

The gliding arc in humid air is a relevant source of free radicals and strongly oxidising species such as HO* (shown by emission spectroscopy), which are able to degrade organic wastes. This feature was used in a new process for mineralising spent tributylphosphate (TBP) which is an important waste from nuclear industry. The degradation kinetics is examined by monitoring the conversion of TBP into phosphoric acid in a batch reactor. The kinetics exhibits three steps and especially an overall zero-order linear step with a rate of 10 mmol h(-1) at the beginning of the treatment. This zero-order step agrees with a surface oxidation process. After a 13.7h treatment, about 45% of the TBP is converted into inorganic phosphorus compounds, with phosphoric acid as the major product (63% of inorganic phosphorus compounds), and at least 19.5% is not degraded. Dibutylphosphoric acid (HDBP) was identified as the main by-product by a nuclear magnetic resonance technique, infrared spectroscopy and gas chromatography.

Lethal effect of the gliding arc discharges on Erwinia spp.

Aims:  To compare the decontamination performances of glidarc on strains of Erwinia of industrial interest.

Destruction of planktonic, adherent and biofilm cells of Staphylococcus epidermidis using a gliding discharge in humid air

Aims: To determine the efficiency of an electric discharge of the gliding arc type for the destruction of Staphylococcus epidermidis planktonic, adherent and biofilm cells.

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

ABSTRACT 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.

Acidity control of plasma-chemical oxidation: applications to dye removal, urban waste abatement and microbial inactivation

Electric discharges burning in humid air at atmospheric pressure over aqueous solutions induce acid effects in the liquid phase resulting from the formation of nitric acid and peroxynitrous acid as transient precursor. These acid effects affect the degradation mechanisms of organic wastes and the relevant kinetic rates; therefore they thus must be controlled (e.g. using buffers). Nitrogen reactive species such as peroxynitrous acid or its salt are directly concerned with both acid effects as precursor to nitric acid, and strong oxidizing properties E?(ONO2H/NO2) = 2.02?V/SHE. Illustrating examples are given in the case of an organic dye (Alizarin S) removal and the gliding discharge treatment of urban wastewaters. Additional arguments are presented to explain the biocidal effect of humid air discharges.

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.