Destruction Kinetics of 2,4 Dichlorophenol Aqueous Solutions in an Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

The processes of degradation of 2,4-dichlorophenol (2,4-DCP) aqueous solutions under the action of atmospheric pressure of DBD in oxygen were studied. The degradation of 2,4-DCP proceeds efficiently, the degree of decomposition reaching 100%. The degradation kinetics of 2,4-DCP obeys a formal first-order kinetic law on concentration of 2,4-DCP. The effective rate constants depend weakly on the experimental conditions and are equal to ~ 2 s^?1. Based on experimental data, the energy efficiency of 2,4-DCP decomposition was determined to be in the range of 0.039–0.173 molecules per 100 eV depending on the experimental conditions. The composition of the products was studied by gas chromatography, chromatography-mass spectrometry, UV/visible spectroscopy, fluorescent methods and some chemical methods. The main decomposition products present in the solution were found to be carboxylic acids, aldehydes and chloride ions, whereas carbon dioxide and molecular chlorine appear in the gas. The results obtained are compared with similar data from other advanced oxidation processes (AOP’s) methods.     

The Destruction of Carbon Tetrachloride Dissolved in Water in a Dielectric Barrier Discharge in Oxygen

The kinetics of decomposition of tetrachloromethane (TCM) in its aqueous solutions and the kinetics of decomposition products formation was investigated under the action of DBD at atmospheric pressure in oxygen in a falling-flow reactor. The range of initial concentrations of TCM was 25–325 μmol/l, the discharge power—2–11 W and O₂ flow rates—1–3 cm³/s. It is shown that the kinetics of the TCM decomposition can be described by the equation of pseudo-first kinetic order. The rate constant depended weakly on the discharge parameters and was?~?5 s^?1. The energy efficiency of the decomposition, depending on the parameters, was 0.1–1.3 molecules per 100 eV. When the residence time of the solution with the discharge zone is more than 1 s, it is possible to achieve almost 100% degree of TCM decomposition. It is shown that the main products of the TCM decomposition in the liquid phase are aldehydes and Cl^? ions, and in the gas phase—the molecules CO and CO₂. The results for energy efficiency are compared with the results obtained in other AOP’s processes (Fenton process, photocatalytic process, the radiation process by the action of high-energy electron flux). It is shown that the action of the DBD is more effective than the action of the above processes.

     

Application of Dielectric Barrier Discharge for Waste Water Purification

This study considers treatment of real city rain sewage under the action of an oxygen dielectric barrier discharge (DBD) at atmospheric pressure in the presence or absence of TiO₂ catalyst in the plasma zone. The DBD discharge has been shown to have high decomposition efficiency (up to 98%) for oil hydrocarbons, phenols and synthetic surfactants. The discharge action resulted in the decrease of heavy metal (Pb, Cd, Fe, Mn) content as well. In a plasma-catalytic hybrid process, the efficiency of organic substances decomposition was higher than efficiency for the DBD treatment without catalyst.     

Water Purification to Remove Naphthalene by Treatment with Dielectric-Barrier Discharge in Oxygen

High Energy Chemistry - The destruction of naphthalene (NAP), one of polycyclic aromatic hydrocarbons, in its aqueous solution by treatment with atmospheric-pressure dielectric-barrier discharge in...     

Destruction of 2,4-Dichlorophenol in Water Solution Using a Combined Process of Sorption and Plasma Exposure to DBD

The results of studies of the decomposition of 2,4-dichlorophenol (2,4-DCP) in its aqueous solution under the action of atmospheric pressure DBD in an oxygen flow are presented. A new reactor design was used in which the discharge zone was filled with a sorbent (diatomite). It was found that the kinetics of decomposition obeys a first-order kinetic equation for the concentration of 2,4-DCP. The presence of an adsorbent significantly improves the parameters of the decomposition process. Decomposition rates, rate constants and energy efficiency are doubled. So, at a specific discharge power of 1.8 W/cm³ in the presence of a sorbent, the rate constant was ~1 s^?1, and without it, ~0.5 s^?1. The energy efficiency was 0.031 and 0.016 molecules per 100 eV, respectively. The parameters of the treated solution are improved in terms of its potential toxicity. The concentrations of the main decomposition products (aldehydes, carboxylic acids) in the presence of a sorbent are significantly less than without it. This is due to an increase in the rate of conversion of these products into carbon dioxide molecules. It was also shown that the decomposition of one 2,4-DCP molecule leads to the formation of two chloride ions in solution, and the ozone formed in the discharge does not significantly affect the destruction process.

     

Destruction of 2,4 Dichlorophenol in an Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

The processes of degradation of 2,4-dichlorophenol (2,4-DCP) under the action of atmospheric pressure of dielectric barrier discharge (DBD) in oxygen were studied. It was shown that the degradation of 2,4-DCP proceeds efficiently. Degree of decomposition reaches 90%. The degradation kinetics of 2,4-DCP obeys the formal first-order kinetic law on concentration of 2,4-DCP. The effective rate constants depend weakly on the experimental conditions and are equal to ~0.2 s^?1. Based on experimental data, the energy efficiency of decomposition of 2,4-DCP was determined. Depending on the conditions, the energy efficiency was in the range of (8–90) × 10^?3 molecules per 100 eV. The composition of the products was studied by gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), energy-dispersive X-ray spectroscopy (EDX), attenuated total reflection-fourier transform infrared (ATR-FTIR) spectroscopy, electron spin resonance (ESR) spectroscopy and UV/Visible spectroscopy. It was shown that about ~20% of 2,4-DCP is converted to CO₂, while the other part forms an organic film on the reactor wall. The substance formed is close to the carboxylic acids in chemical composition and exhibits electrical conductivity and paramagnetic properties. Almost all of the chlorine contained in the 2,4-DCP is released into the gas phase. The active species of the afterglow react with liquid hexane, forming the products of its oxidation. Some assumptions regarding the pathway of the process are discussed.     

Removal of Oil Products from Water Using a Combined Process of Sorption and Plasma Exposure to DBD

The paper presents the results of studies of a combined process involving the sorption of engine oil on a sorbent (diatomite) followed by regeneration of the sorbent by plasma-oxidative destruction of oil in DBD of atmospheric pressure in oxygen. The process parameters (gas flow rate, sorbent mass, power, treatment time), which provide the possibility of fivefold regeneration of the sorbent and 100% degree of oil decomposition, are revealed. It was found that the kinetics of oil degradation obeys the pseudo-first kinetic order equation with a rate constant of 0.017 s^?1. The energy efficiency of the decomposition was 0.169 molecules of oil per 100 eV of input energy. It is shown that treatment of the sorbent for 5 min leads to the complete decomposition of oil. The products of oil decomposition are carboxylic acids, aldehydes and CO₂. Complete removal of acids and aldehydes requires the time of about 40 min. The possible participation of ozone in the oxidative degradation of oil is discussed.