Decomposition of сarbon tetrachloride under the action of a dielectric barrier discharge of atmospheric pressure in an oxygen atmosphere

In this study, the process of decomposition of carbon tetrachloride (CCl₄) vapor in oxygen DBD at atmospheric pressure and its kinetic regularities have been studied. In the course of the experiments, it was shown that the efficiency of the decomposition of carbon tetrachloride in DBD can reach 100%. Depending on the conditions of the experiments, the effective rate constants were equal to (0.16-0.59) s^-1, and the decomposition energy yields were (0.001-0.012) molecules per 100 eV of the inputed energy. The main decomposition products were CO₂ and Cl₂ molecules. The formation of a solid on the internal electrode of the reactor was also found. The substance contains atoms of carbon, oxygen, chlorine (C:O:Cl) = 1:0.38:0.01, as well as hydrogen atoms. The substance also contains functional groups -CH, -CH₂, -OH and dimers of carboxylic (chlorocarboxylic) acids. Based on the solution of the Boltzmann equation for electrons, it is shown that for the compositions of a gas containing O₂ molecules, ССl₄, and decay products, the kinetic and transport characteristics of electrons are the same as in a pure oxygen discharge. Using the kinetic characteristics of electrons and the reaction rate constants the mechanisms of reactions leading to the found reaction products are proposed. It was shown that the primary reaction of destruction is the reaction of dissociation of CCl₄ by electron impact, leading to the formation of CCl₃^• and Cl and the reaction with the O (¹D) atom, as a result of which CCl₃^• and ClO^• are formed.

Distribution of Policyclic aromatic hydrocarbons in a snow cover in the territory of Ivanovo city, Russia

The paper presents the results of a study of the content of 12 polyaromatic hydrocarbons (PAHs) in the snow cover of the city of Ivanovo (Russian Federation). It is shown that their average content exceeds the background level by 6.6 times, which made it possible to identify for which compounds the admission channels are associated with transboundary transport (naphthalene, pyrene, benz [b]fluorantin, benzo [a]pyrene and dibenz [a,h]anthracene), and for which with local emission sources (anthracene, phenanthrene, fluoranthene, chrysene, benz [k]fluorantin, and benzo [g,h,i]perylene). According to the known indicator ratios of the concentrations of PAHs, the main sources of release (pyrogenic and mixed) PAHs into the environment were estimated. The combination of experimental data in combination with factor analysis allowed identifying priority PAHs (naphthalene, fluoren, fluoranthene, benzo [a]pyrene and benzo [g,h,i]perylene), which should be included in the environmental monitoring programs of the region. Environmental risk assessments are given, which showed that the level of pollutant does not always adequately reflect the environmental impact for the territories. Thus, the contribution to the total PAH concentration of benz [b]fluorantin is only 9%, and to the amount of environmental risk - 51%. This must be taken into account in order to prioritize the control of individual components of PAHs in environmental objects.

INFLUENCE OF BENZO(A)PYRENE ON ENVIRONMENTAL QUALITY AND POPULATION HEALTH (BY EXAMPLE OF IVANOVO)

The paper presents the results of measurements of the content of benzo(a)pyrene (BaP) in the snow cover in the territory of the Ivanovo city. It was revealed that the concentration of BaP at the controlled points is 2.7 times higher than the background level on average. The degree of pollution of the snow cover in Ivanovo is much less than in Moscow (the level of excess varies in the range 2.3 - 89 times). The intake levels (from 0.02 μg/m2 to 3.76 μg/m2) and deposition density (0.02 - 1.88 ng/m2 · day-1) of BaP are estimated that are commensurate with the values typical for such areas, as urban areas of Germany and Canada. Interpolation the BaP concentrations in snow is allowed to reveal anomalies in the city with BaP content of 35 ng/l, which is 7 times higher than the average value for the whole city. The obtained data made it possible to estimate the BaP concentration in atmospheric air, which on the average is 0.7· 10-6 mg/m3, which is 0.7 fraction of the maximum permissible concentration. The values of individual carcinogenic risk for public health were calculated, which amounted to 0.6·10-6 and 1.6·10-6, which corresponds to negligible individual risk (for the adult population) or corresponds to the maximum allowable level (for children), respectively. The obtained results allowed to evaluate the environmental risk from pollution of the snow cover with BaP, the level of which corresponds to a moderate one, however, indicates a potential public health hazard related to the ability of the BаP to accumulate in environmental objects. It is established that the most likely source of BaP is automobile transport. The contribution of the fuel and energy complex should be much less.

DESTRUCTION OF OIL HYDROCARBONS IN WATER SOLUTIONS WITH OXYGEN DIELECTRIC BARRIER DISCHARGE OF ATMOSPHERIC PRESSURE

This paper reports the experimental study of destruction kinetics of oil hydrocarbons (engine oil of the M8 trademark) dissolved in water by dielectric barrier discharge in oxygen at the atmospheric pressure. The range of initial concentrations of oil in the aqueous solution was (12- 91) mg/l. All experiments were carried out under the applied voltage of 7.9 kV and discharge current of 0.45 mA (rms values) with a frequency of 50 Hz. The inputted power was 0.35 W/cm3.  The gas flow rate was 1 l/min. It was shown that the kinetics of oil decomposition can be formally described by the pseudo-first order law on oil concentration. The effective rate constant for decomposition of petroleum products was 0.0016 s-1. The rate of destruction in the investigated concentration range of M8 was varied in the range (3.8 - 28.9) · 10-6 mol / (l·min). The oil decomposition degree achieved 80 %, and the decomposition energetic yield was 0.16 molecules per 100 eV of inputted energy. The kinetics of the formation of ozone and carbon dioxide was examined as well. The obtained experimental data allowed to determine the degree of completeness of oil oxidation, which at the maximum was 54% (for carbon dioxide), this results indicates the formation of other carbon-containing compounds. The dynamics of the change in the pH of the treated solution is revealed. Under the experimental conditions, the pH was reduced from 6 to 4. It was found that the concentration of ozone formed in the reactor was deficiency for oil oxidative degradation. This results confirms that in the system are formed other active particles involved in the destruction of petroleum products, such as the OH* radicals and atomic oxygen. The possible mechanism of degradation processes is discussed.Forcitation:Grinevich V.I., Rybkin V.V., Lyubimov V.A., Gushchin A.A. Destruction of oil hydrocarbons in water solutions with oxygen dielectric barrier discharge of atmospheric pressure. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 20-27.