• Journal of Korean Society of Water and Wastewater
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• v.33 no.4
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• pp.243-250
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• 2019

This objective of this study was to investigate the degradation characteristics of phenol, a refractory substance, by using a submerged dielectric barrier discharge (DBD) plasma reactor. To indirectly determine the concentration of active species produced in the DBD plasma, the dissolved ozone was measured. To investigate the phenol degradation characteristics, the phenol and chemical oxygen demand (COD) concentrations were evaluated based on pH and the discharge power. The dissolved ozone was measured based on the air flow rate and power discharged. The highest dissolved ozone concentration was recorded when the injected air flow rate was 5 L/min. At a discharge power of 40W as compared to 70W, the dissolved ozone was approximately 2.7 - 6.5 times higher. In regards to phenol degradation, the final degradation rate was highest at about 74.06%, when the initial pH was 10. At a discharged power of 40W, the rate of phenol decomposition was observed to be approximately 1.25 times higher compared to when the discharged power was 70W. It was established that the phenol degradation reaction was a primary reaction, and when the discharge power was 40W as opposed to 70W, the reaction rate constant(k) was approximately 1.72 times higher.

• Journal of ILASS-Korea
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• v.25 no.3
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• pp.132-138
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• 2020

N₂O is hazardous atmosphere pollution matter which can damage the ozone layer and cause green house effect. There are many other nitrogen oxide emission control but N₂O has no its particular method. Preventing further environmental pollution and global warming, it is essential to control N₂O emission from industrial machines. In this study, the thermal decomposition experiment of N₂O gas mixture is conducted by using cylindrical reactor to figure out N₂O reduction and NO formation. And CHEMKIN calculation is conducted to figure out reaction rate and mechanism. Residence time of the N₂O gas in the reactor is set as experimental variable to imitate real SNCR system. As a result, most of the nitrogen components are converted into N2. Reaction rate of the N₂O gas decreases with N₂O emitted concentration. At 800℃ and 900℃, N₂O reduction variance and NO concentration are increased with residence time and temperature. However, at 1000℃, N₂O reduction variance and NO concentration are deceased in 40s due to forward reaction rate diminished and reverse reaction rate appeared.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.540-543
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• 2010

In this study, we made low temperature plasma reactor in order to treat safely $NO_x$ which included in the gas. We investigated experimently and inspected efficiency characteristics of equipment about flow rate of reactant material and discharge input power which supplied into reactor. As a reaction gas, by using mixture gas of $NO/N_2$ and $N_2/O_2$, we setted up initial NO concentration and supplied the speed of a current to 1~4 l/min. When the amount of flow increased, reduction rate of NO was low. Also when discharge input power was high, decomposition of NO was easy. Also the longer delay time of reaction material and the higher discharge input power was, the higher decomposition energy efficiency was. And when the amount of flow was much, and the more discharge input power increased, the more ozone generated.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.869-877
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• 2000

A mechanism of ozonation of simulated soil slurry contaminated by phenanthrene and benzo[a]pyrene has been studied under various conditions. The effects of soil media(BS, S, GB), radical scavenger, ozone input ratio(0.17~0.73mg/min), bicarbonate ion, and humic acid were investigated, BS showed the highest removal efficiency in media tested. The generation of OH-radical via the catalytic decomposition of ozone on active sites of the natural sand was confirmed by OH-radical scavenger experiments. The enhanced removal efficiency by OH-radical was indirectly quantified to be about 22%. As initial concentration of humic acid(as sodium salt) was increased, pseudo first-order rate constant ($k_o$) of phenanthrene was decreased from $1.37{\times}10^{-2}s^{-1}$ to $0.53{\times}10^{-2}s^{-1}$. The amount of ozone required to oxidize 80% of the initial mass of phenanthrene(10mg/kg) and benzo[a]pyrene(10mg/kg) was 67.2mg/kg-soil and 48.0mg/kg-soil, respectively.

• Journal of Soil and Groundwater Environment
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• v.6 no.1
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• pp.3-12
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• 2001

During ozonation process, the hydroxyl radical generation rates were measured under different experimental conditions (ozone feed rate, nitrobenzene concentration, hydroxyl radical scavenger, pH, HO$_2$O$_2$/O$_3$ etc.) Nitrobenzene could be decomposed by hydroxyl radical rather than ozone only and nitrobenzene decomposition rate was expressed with functions of ozone and nitrobenzene concentration. The rate was decreased as the hydroxyl radical scavenger concentration was increased, and all results were followed pseudo first-order reaction. Using a competitive method, hydroxyl radical generation rate was measured with probe compound and scavenger. It was proportional to ozone concentration, and 0.24mo1 of hydroxyl radical was produced with 1mol of ozone. Under different pH conditions, hydroxyl radical generation rates were measured (pH 10.2 (0.91Ms$^{-1}$ ) > pH 7.3 (0.72Ms$^{-1}$ ) > pH 5.6 (0.67Ms$^{-1}$ ) > pH 3.4 (0.63Ms$^{-1}$ )) showing higher generation rate at high pH values. Addition of hydrogen peroxide promoted the generation rate of hydroxyl radical. Considering the results of pH experiments and addition of hydrogen peroxide experiments, the hydroxyl radical generation rate was 1.6 times higher in hydrogen peroxide solution than in high pH solution, indicating addition of hydrogen peroxide is better promoter to produce the hydroxyl radical in ozonation. These results could be applied to AOPs to remediate the contaminated wastewater and groundwater.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.83-90
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• 2006

Performance and operation of BAC in ozone-BAC advanced water treatment process were investigated using the pilot scale test plant built in D water purification plant. The performance was evaluated by the removal efficiencies of DOC, BDOC, ammonia nitrogen and THMs. The effect of EBCT on DOC removal was experimented for an effective operating condition, and the amount of attached biofilm was analyzed in various water temperatures and position of BAC. Two removal mechanisms, adsorption and biological decomposition by attached biofilm, were predominant to decrease the concentration of various contaminants. DOC was removed 40%, and the removal rate was decreased in winter time due to the lowered activity of attached biofilm. BDOC was effectively removed. THMs and ammonia nitrogen were mainly removed not in ozonation process but in BAC. Water temperature deeply influenced in removal efficiency of ammonia nitrogen. The amount of attached biofilm depended on water temperature and height of packed activated carbon column. Considering DOC removal efficiency and design EBCT of commercial BAC plant, the proper EBCT was 12.5 minutes.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.3
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• pp.5-12
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• 2017

Effects of operating parameters such as activated carbon dose, gaseous $O_3$ concentration and pH on the properties of methylene blue(MB) degradation in a catalytic ozonation were investigated through a series of batch experiments. Activated carbon catalyzed the self-decomposition of ozone, generating $OH{\cdot}$, thus promoting MB degradation. Thus the increase of activated carbon dose enhanced the MB and TOC removal. The higher gaseous ozone concentration injected, the promoted MB and TOC removal obtained through the enhanced mass transfer. The MB removal was not significantly affected by the variation of aqueous pH. Catalytic ozonation can be considered as an efficient alternative in treating refractory pollutants in textile wastewater with faster and higher dye and TOC removal compared with ozonation and adsorption.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.7
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• pp.412-417
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• 2017

Removal characteristics of methyl orange and their dependence on operating parameters in a catalytic ozonation were investigated through a series of batch experiments. Activated carbon enhanced the self-decomposition of ozone, generating $OH{\cdot}$, thus promoting methyl orange degradation. As the carbon dose increases, the pseudo-first order rate constants of methyl orange degradation increased, resulting in the fast removal of methyl orange. The increase of gaseous ozone concentration enhanced the mass transfer to the aqueous solution, therefore, promoted the methyl orange removal. The methyl orange degradation was not significantly affected by the change of pH in the range of 5~12, and TOC removal was negligibly affected by the variation of pH over 7. The results indicate that the catalytic ozonation can be considered as an effective dye treatment technology.

• Journal of the Korean Chemical Society
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• v.36 no.5
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• pp.644-651
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• 1992

The kinetics of the gas phase reaction of ozone(∼0.5 torr) with sulfur trioxide was investigated in the range of 6∼12 torr pressure at 69∼150${\circ}C$. The reaction rate of ozone with sulfur trioxide was faster than the reaction rate of $O_3 in the presence of CO_2 alone. No evidence for a molecular reaction of O_3 with SO_3 was found and the faster rate is probably due to impurity (HX) from the SO_3 reactant which gives rise to a chain reaction initiated by O_3 ＋ HX → OH ＋ O_2 ＋ X and also SO_3 has a larger collision diameter, which may be attributed to the O3 thermal decomposition more feasibly. The proposed experimental law [-d(O_3)/dt] = k_a(SO_3)(O_3) ＋ k_b(O_3)^{3/2} gives a rate constant ka(M-1 s-1) = (1.55 {\pm} 0.67) {\times} 105 e-{(9.27 0{\pm}0.43)kcal/RT}.$

• Analytical Science and Technology
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• v.35 no.5
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• pp.212-217
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• 2022

In this study, ozone (O₃) samples were prepared for investigating the heterogeneous reactions between O₃ and tropospheric aerosols and were characterized by spectroscopic methods. O₃ generated from an ozone generator was purified by selective adsorption on refrigerated silica gel, followed by transfer to a sample bulb. The amount of UV light (λ = 256 nm) absorbed by O₃ was measured as a function of time at two different temperatures (room temperature and 50 ℃) and under different irradiation conditions. A correlation plot of 1/[O₃] versus time showed that O₃ decomposition follows the 2^nd order reaction rate under a steady-state approximation. The initial concentration of O₃, observed rate constants (k_obs), and the half-life of O₃ in the sample stored at room temperature were determined to be 2.74 [±0.14] × 10¹⁶ molecules·cm^-3, 4.47 [±0.64] × 10^-23 molecules^-1·cm³·s^-1, and 9.5 [±1.4] days, respectively. The evaluation of O₃ stability under various conditions indicated that special care should be taken to prevent the exposure of the O₃ samples to hightemperature environment and/or UV radiation. This study established a protocol for the preparation of highly purified O₃ samples and confirmed that the O₃ samples can be stored for a day after preparation for further experiments.