• Journal of Korean Society on Water Environment
• /
• v.30 no.4
• /
• pp.394-402
• /
• 2014

High-voltage dielectric discharges are an emerging technique in environmental pollutant degradation, which are characterized by the production of hydroxyl radicals as the primary degradation species. The initiation and propagation of the electrical discharges depends on several physical, chemical, and electrical parameters such as 1st and 2nd voltage of power, gas supply, conductivity and pH. These parameters also influence the physical and chemical characteristics of the discharges, including the production of reactive species such as OH, $H_2O_2$ and $O_3$. The experimental results showed that the optimum 1st voltage and oxygen flow rate for RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation were 160 V (2nd voltage of is 15 kV) and 4 L/min, respectively. As the 2nd voltage (4 kV to 15 kV) was increase, RNO degradation was increased and, generated $H_2O_2$ and $O_3$ concentration were increased. The conductivity of the solution was not influencing the RNO degradation, $H_2O_2$ and $O_3$ generation. The pH effect on RNO degradation was not high. However, the lower pH and the conductivity, the higher $H_2O_2$ and $O_3$ generation were observed.

• Journal of Environmental Health Sciences
• /
• v.38 no.2
• /
• pp.159-165
• /
• 2012

Objectives: This experiment was carried out to elucidate the effect of discharged water on the disinfection of $Phytophthora$ $capsici$ and evaluate the water characteristics. Methods: The dielectric barrier discharges (DBD) plasma reactor system used in this study consisted of a plasma component [discharge, ground electrode and quartz dielectric tube], high voltage source, and air supply. The effects of water characteristics such as pH, ORP and conductivity and the disinfection effect of discharged water were investigated. Results: Experimental results showed that in the process of discharge, the pH decreased, whereas ORP and electric conductivity increased. When the discharge time was 30 min, $Phytophthora$ $capsici$ of 2.94 log was disinfected within 300 seconds. Disinfection performance of stored discharged water was maintained for three days; however the disinfection effect vanished after five days. When $Phytophthora$ $capsici$ was injected into the discharged water, the disinfection effect decreased after two days. Conclusions: It is considered that the main disinfection parameters of the discharged water were chemically active species such as $H_2O_2$ and $O_3$ and high ORP.

• Journal of Environmental Science International
• /
• v.24 no.7
• /
• pp.947-954
• /
• 2015

Dielectric barrier discharge plasma is a new technique in water pollutant degradation, which that is characterized by the production of chemically active species such as hydroxyl radicals, ozone, hydrogen peroxide, etc. If dissolving of plasma gas generated in the plasma reaction has increased, it is possible to increase the contaminant removal capacity. In this study, the improvement on the dissolving performance of plasma gas was evaluated by the indirect method measuring the overall oxygen transfer coefficient. Experiments were conducted to examine the effects of nozzle type, distance from water surface, air supply rate and liquid circulation rate. The experimental results showed that the $K_{La}$ value of the 3-prong nozzle is 2.67 times higher than the diffuser. The order of $K_{La}$ value with nozzle type ranked in the following order: 3-prong nozzle (inner diameter, less 1 mm) > circular nozzle (inner diameter, 1.5 mm) > ellipse nozzle (short diameter 1 mm, long diameter 2.5 mm) > circular nozzle (inner diameter, 3 mm). Optimal liquid circulation rate was appeared to be 1.7 L/min, the value of $K_{La}$ was 0.510 1/min. The value of $K_{La}$ with increasing air supply rate was revealed in the form of an exponential such as $K_{La}=0.3581e^{0.2919^*air\;flow\;rate}$.

• Carbon letters
• /
• v.8 no.4
• /
• pp.280-284
• /
• 2007

Samples of active carbon of $1150\;m^2/g$ surface area were impregnated with ammoniacal salts of copper, chromium and silver, with and without triethylenediamine. The samples of impregnated carbon were aged at $50^{\circ}C$, with and without 90% RH (relative humidity), for a little more than one year and chemically evaluated periodically. Initially copper (II) and chromium (VI) reduced very fast in the samples in humid atmosphere to the extent of 30% and 60% respectively in four months. These values were found to be unaffected by the presence of triethylenediamine (TEDA) indicating that the chemical did not retard the reduction process of chromium (VI) and copper (II). However, in the absence of humidity the reduction of the impregnants was significantly less (10-12%, w/w) in four months. It was quite evident; therefore, that the moisture was mainly responsible for the reduction of chromium (VI) and copper (II) species in impregnated carbons. The prolonged ageing of the samples with and without triethylenediamme after four months with and without humid atmosphere showed that the extent of reduction of chromium (VI) was very low, i.e. 5-10% and of copper (II) was 2-25%. Silver is not reduced due to carbon, as it remained unchanged in concentration on storage. The impregnated carbon samples (100 g) without triethylenediamine, which were aged at room temperature for 5 years in absence of humidity and unaged when evaluated against cyanogen chloride (CNCl) at a concentration of 4 mg/L and airflow rate of 30 lpm showed a high degree of protection (80- 110 minutes).