Eugen Hnatiuc

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.

How various plasma sources may affect seed germination and growth

Germination and early growth of buckwheat (Fagopyrum aesculentum) after low-temperature plasma discharge treatment in air gas generated in various devices were tested. Three pre-treatment times were used: 180 s, 300 s and 600 s. Seed cultivation was carried out in laboratory conditions. Number of germinating seeds was counted, length and weight of seedling sprouts were measured. The data were analysed with two-way ANOVA: a significant influence of the type of plasma apparatus, time of exposure and combination of both factors were found. A positive effect on germination and early growth was observed after the application of GlidArc device (low-temperature plasma generated in air gas under atmospheric pressure between two electrodes). The opposite effect of surface dielectric barrier discharge (SDBD) apparatus, which is characterized by plasma with high power density, was observed. Shorter pre-treatment times for SDBD device must be therefore used. Effects of seed germination and early growth of seeds strongly depended on the type of the used plasma apparatus.

Gliding discharge-induced oxidation of a toxic alkaloid

The gliding discharge is a quenched plasma source suitable for the plasma treatments of liquids since it is operated in quasi-normal T and P conditions. Discharges in wet air provide a flow of strongly oxidizing radicals, e.g., NO and HO, able to oxidize and mineralize many organic pollutants in aqueous solution. The present paper reports on the destruction of nicotine, a toxic alkaloid from tobacco used as insecticide. Mineralization was monitored by total organic carbon (TOC) analysis and obeyed an overall first order kinetics mechanism. Carbon dioxide formation was followed by specific reactive Dräger tubes. The influence of the airflow rate was considered.

The study of an electric spark for igniting a fuel mixture

The ignition sparks provided by the classical system do not always assure a fast and complete combustion of the hydrocarbon-air mixture. For this reason have been made a lot of studies, most of them trying to implement new types of electronic ignition systems, including power supply and the spark plug itself, which must provide faster, more complete and more efficient-fuel burning, so overall a lower impact on the environment. The aim of such system consists in the generation of an electrical discharge between the spark plug electrodes able to assure a larger and more homogenous volume of the plasma in the engine cylinder. The implementing of such a system involves conducting complex electrical, mechanical, chemical and physical analysis, to validate its benefits in comparison to the classical system. The new type of ignition system with two sparks uses a spark plug with three electrodes. The first one is connected at the high voltage, the second at the ground and the third, located between the two others, free of potential. This paper proposes a complex and comparative study to the classical ignition system. Measurement of the electrical parameters and the physical analysis were done mainly by testing ignition systems in a reactor with air. The mechanical and chemical parameters were measured using an engine stand four-stroke.

A correlation between the rotational temperature and the electrical energy of a cold plasma type electrical discharge produced by a double spark-plug

To improve the combustion process of the air-fuel mixture into the combustion chamber of the engines, an ignition system based on a three electrodes spark-plug and a microcontroller based supply has been proposed. The benefits which can be achieved by using the new system are: reduction the amount of some pollutants such as unburned hydrocarbons from the exhaust gases, improving the engines efficiency, fuel consumption decreasing and also some unwanted engine processes (misfires, hesitations, detonations, stutters and stumbles) can be avoided. The first phase of the validation process of the new ignition system was to perform a diagnosis of the plasma produced using the new spark plug and to compare the results with the ones obtained from the diagnosis of the plasma produced by a classical spark plug. Also the electrical parameters were measured for both the spark plugs and for different waveforms of the control signals. In this paper we present a correlation between the rotational temperatures of the plasma and the energy consumed by the discharges produced using the classical and the double spark plugs. The spectra used to determine the rotational temperatures have been recorded in air at atmospheric pressure using a spectrometer equipped with a CCD camera. The electrical discharge voltage and current measurement used to calculate the energy of the discharge have been made in air using a high voltage probe and a shunt resistance.

The ignition and control condition for the useful discharge in a GlidArc reactor with plane geometry and auxiliary electrodes

The paper refers to the optimal operation of GlidArc type cold plasma plane-symmetrical electrochemical reactors with auxiliary electrodes and proposes the correct definition for the position of the auxiliary electrodes when designing the device. This proposes considering the capacities that characterize the ignition and distribution of the pilot electrical discharge between the E1 - A1 - A2 - E2 electrodes and defines the analytical optimal operation condition for the device, leading to an irrational equation having the position of the auxiliary electrodes as solution. Highly correlated with experimental observations, it is found that one or two positions of the auxiliary electrodes can be defined for the convenient evolution of the auxiliary discharge, allowing the command and control of the main electrical discharge in a GlidArc reactor.

About the operation of the cold plasma GlidArc type reactors with rotary discharge and auxiliary electrodes

The cold plasma type electrochemical reactors are more often used for different applications such air or solutions decontamination, surfaces treatment and in some cases for bio-decontamination or even sterilization [1]. In the last decade, in the medicine field, several applications have been developed which assure bio-compatibility of the implant materials or even are used to treat living tissues (postsurgical or for skin disorders). The utilizations of the auxiliary electrodes in the construction of the GlidArc reactors confer on them the possibility to command and to control the main discharge, obtaining in this way certain benefits for the applications which use such devices [2], [9], [11]. Following the innovative solutions of the GlidArc type electrochemical reactors with auxiliary electrodes and planar discharge, volumic discharge or rotary discharge proposed by our research team, [3], [4], this paper aims are to present a appropriate mathematical model regarding the operation of the reactors with rotary discharge and auxiliary electrodes. In this way can be defined the fact that there is only one possible position of the auxiliary electrodes for which the command and the control of the discharge can be assured in the case of the reactors with rotary discharge comparing with the case of the reactors with planar symmetry where there are two possible positions of the auxiliary electrodes. Using the proposed mathematical model can be highlighted the influence of different constructive factors on the discharge evolution. The practice experience in implementation of the GlidArc type reactors with auxiliary electrodes is fully confirmed by the results offered by the mathematical model proposed in this paper.

The evolution of aqueous solutions properties exposed to a GlidArc discharge

Plasma technologies are considered today by many experts as a new field for new discoveries, with many practical applications in the most various domains of the human activities: chemistry, medicine, industry (food, textiles, steel), etc. The evaluation of all physical and chemical parameters of the plasma leads to a better understanding of the processes that occur during the interaction with various organic or inorganic compounds. The goal of this paper is to study the effect of non-thermal plasma treatment on water and organic solute (soluble dyes) and it aims to examine the intervention of the electrical discharge generated by different types and power inputs of electrochemical reactors, i.e. cold plasma, on pH sensitive substances. This can lead to properties changes of samples and also can be dangerous for the humans.

Hydrogen and hydrogen peroxide formation in the AC water-spray gliding arc reactor

The goal of this paper is to study the formation rates and energy yields of H2 and H2O2 formed from pure water exposed to a non-thermal AC plasma-gliding arc reactor equipped with a spray nozzle. The gliding arc reactor utilizes an AC electrical discharge developed in a gas flowing between two electrodes supplied by one high voltage transformer. Previous works [1, 2, 3] showed that the efficiency of reactive and molecular species formation in water treated by non-thermal plasma depends on the gas-liquid interfacial contact area between the water and the plasma zone. Spraying the liquid through a special two-way nozzle directly into the plasma zone is an effective method to enhance the efficiency of chemical species formation in gliding arc reactors. In the present work, the focus is on hydrogen formation from water spray exposed to plasma generated by an AC gliding arc discharge using Ar as carrier gas for different electrical powers of the discharge and for different water flow rates. The formation rates of hydrogen and hydrogen peroxide were also determined.

Zirconium and titanium surface treatment using non-thermal plasma for dentistry applications

The cold plasma reactors are more often used in the last decades in surface treatment and bio-decontamination. The aim of this paper is to present the GlidArc plasma effects on the material surfaces used in dentistry (zirconium and titanium plates). For the conducted tests two GlidArc reactors were used: the first one having two electrodes, producing a planar electrical discharge and the second one with three electrodes and volumic discharge. Keeping the treatment time constant (60 seconds) the nature of the blowing gas used (humid and dry air) and the distance between the plasma and the treating samples was modified. The surfaces were analyzed performing atomic force microscopy (AFM) in air at room temperature. Both topographical and adhesion force measurements were considered as parameters used for characterizing the morphological modifications of the surfaces induced by the plasma treatment.