• Journal of Korean Society for Atmospheric Environment
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• v.29 no.1
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• pp.27-37
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• 2013

CFCs (Chlorofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) that are chemically stable were proven to be a greenhouse gases that can destroy ozone layer. On the other hand, HFCs (Hydrofluorocarbons) was developed as an alternative refrigerant for them, but HFCs still have a relatively higher radiative forcing, resulting in a large Global Warming Potential (GWP) of 1,300. Current regulations prohibit production and use of these chemicals. In addition, obligatory removal of existing material is in progress. Methods for the decomposition of these material can be listed as thermal cracking, catalytic decomposition and plasma process. This study reports the development of low cost and high efficiency plasma scrubber. Stability of steam plasma generation and effect of plasma parameters such as frequency of power supply and reactor geometry have been investigated in the course of the development. Method for effective removal of by-product also has been investigated. In this study, elongated rotating arc was proven to be efficient in decomposition of HFCs above 99% and to be able to generate stable steam plasma with steam contents of about 20%.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.567-572
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• 2005

In this study, a lab-scale test was performed to apply the ozone process in drinking water treatment plant using dissolved ai, flotation(DAF). The kinetic study on the ozone decay and hydroxyl(OH) radical formation was investigated by several parameters, such as I.D(Instantaneous ozone demand), $k_c$(ozone decomposition rate), ozone-Ct and OH radical-Ct. Ozonation of several target waters, such as raw water, DAF treated water and filtrate, was conducted to select the optimum position and dosage of ozone process. The highest value of Ozone-Ct and OH radical-Ct was observed at DAF treated water at initial run time($0{\sim}30\;min$). From the results of ozonation, the intermediate ozonation was proposed as the optimum position and the effective dose of ozone was determined to be $1{\sim}2\;mg/L$.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.251-255
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• 2004

Laboratory experiments were performed to investigate oxidation system using ozone and hydrogen peroxide for treating water contaminated with phenol. We were able to greatly improve the oxidation efficiency of the aqueous phenol using hydrogen peroxide and ozone. Two methods were compared and analyzed in this study. In the consequence through the methods, we concluded that the $O_3/UV$ is superior to the hydrogen the results. The decomposition efficiency of aqueous phenol by $H_2O_2$. was exceeded at 83.3% in the concentration of phenol, 5, 15, 25 ppm, respectively. The rate of decomposition reaction by $H_2O_2$. was very slow. In the occasion of the fractional life, it was determined the value that $1.61{\times}10^{-5}(l/mol)^{1.172}sec^{-1}$, $3.75{\times}10^{-5}(l/mol)^{0.792}sec^{-1}$, $4.11{\times}10^{-5}(l/mol)^{1.782}sec^{-1}$. The rate of decomposition reaction of aqueous phenol by $O_3$ was fast compared to the $H_2O_2$. We concluded that the $O_3$ method is useful with the consideration of the reaction time 30 minutes. In the occasion of the fractional life, it was determined the value that $1.094{\times}10^{-4}(l/mol)^{0.933}sec^{-1}$, $2.1{\times}10^{-4}(l/mol)^{0.842}sec^{-1}$, $7.22{\times}10^{-4}(l/mol)^{1.332}sec^{-1}$.

• Journal of Korean Society on Water Environment
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• v.16 no.4
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• pp.479-490
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• 2000

This study investigated the removal characteristics, Microcystin decomposition and generation of by-products when aqueous Microcystis sp. is oxidized by ozone. The concentration of Microcystin (MC) in aqueous solution has been found by HPLC analysis to decrease continuously by ozonation after the initial, abrupt increase. The kinetic constant of the decomposition of MC-RR and -LR were 0.0596 and 0.0243, respectively. This means that removal efficiency of MC-RR by its oxidative decomposition is preferable compared with that of MC-LR. On the other hand, it has been found that the decomposition product, TOC, exhibits the continuous decrease in the concentration by further ozonation, while DOC and UV-254 increase temporarily until 10 minutes before the decrease. Furthermore, the GC/MSD analysis has revealed that the ozonation of Microcystis sp. for 100minutes affords five kinds of aldehydes, six kinds of alcohols, and trans-1, 2-dimethyl-cyclopropane.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.473-474
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• 2000

Ozone has a potency for disinfection, deodorization, decolorization and decomposition of organic materials by strong oxidation. therefore we used the ozonizer to disinfection and deoderization of a piggery. CFU of the ozonated piggery was lower than the others. And the of ozonizer was redesigned from open-type to close-type to obtain high ozone concentration. We was also investigated the effect of air velocity to ozone concentration.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.39-47
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• 2013

This study demonstrates the oxidative degradation of pharmaceutical compounds during ozonation of surface waters in Ulsan. Diclofenac, carbamazepine, bezafibrate, and ibuprofen were selected as surrogate pharmaceutical compounds, and ozonation experiments were performed using raw waters collected from the Sayeon Dam and the Hoeya Dam in Ulsan. Diclofenac and carbamazepine which have high reactivity with molecular ozone showed higher removal efficiencies than bezafibrate and ibuprofen during ozonation. The addition of tert-butanol, a hydroxyl radical scavenger, increased the removal efficiencies of diclofenac and carbamazepine by increasing the ozone exposure. However, the oxidation of bezafibrate and ibuprofen was inhibited by the presence of tert-butanol due to the suppression of the exposure to hydroxyl radical. The elimination of the selected pharmaceuticals could be successfully predicted by the kinetic model base on the $R_{ct}$ concept. Depending on the experimental condition, $R_{ct}$ values were determined to be $(1.54{\sim}3.32){\times}10^{-7}$ and $(1.19{\sim}3.04){\times}10^{-7}$ for the Sayeon Dam and the Hoeya Dam waters, respectively. Relatively high $R_{ct}$ values indicate that the conversion of $O_3$ into $^{\cdot}OH$ is more pronounced for surface waters in Ulsan compared to other water sources.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.619-625
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• 2017

In this study, the formation of hydroxyl radical and decomposition characteristics of bisphenol A (BPA) was investigated by quantifying hydrogen peroxide formed as a reaction by-product during the formation stage of hydroperoxyl radical. The direct oxidation reaction by ozone only decomposed BPA just like the Criegee mechanism under the condition where radical chain reactions did not occur. Non-selective oxidation reactions occurred under the conditions of pH 6.5 and 9.5 where radical chain reactions do occur, confirming indirectly the formation of hydroxyl radical. The decomposition efficiency of BPA by the added catalysts appeared in the order of $O_3$/PAC ${\geq}$ $O_3/H_2O_2$ > $O_3$/high pH > $O_3$ alone. 0.03~0.08 mM of hydrogen peroxide were continuously measured during the oxidation reactions of ozone/catalyst processes. In the case of $O_3$/high pH process, BPA was completely decomposed in 50 min of the oxidation reaction, but reaction intermediates formed by oxidation reaction were not oxidized sufficiently with 29% of the removal ratio for total organic carbon (TOC, selective oxidation reaction). In the case of $O_3/H_2O_2$ and $O_3$/PAC processes, BPA was completely decomposed in 40 min of the oxidation reaction, and reaction intermediates formed by the oxidation reaction were oxidized with 57% and 66% of removal ratios for TOC, respectively (non-selective oxidation reactions).

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.302-307
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• 2012

Advanced oxidation processes (AOP) such as O3/activated carbon process and O3/catalysts process were used to compare the decomposition of phenol. Catalysts such as Pd/activated carbon (Pd/AC), Mn/activated carbon (Mn/AC), Co/activated carbon (Co/AC) and Fe/activated carbon (Fe/AC) were prepared by impregnation of Pd, Mn, Co and Fe into the activated carbon of pellet form, respectively. Based on an hour of reactions, the following descending order for the decomposition ratios of dissolved O3 to the 1.48 mg/L of saturated dissolved O3 was observed: Mn/AC (45%) > Pd/AC (42%) > Co/AC (33%) > AC (31%) > Fe/AC (27%). The removal efficiencies of phenol were also arranged in the descending order of AOP as follows: Mn/AC (89%) > Pd/AC (85%) > Co/AC (77%) > AC (76%) > Fe/AC (71%). The remaining ratios (C/Co) of TOC (total organic carbon) after an hour of experiments were arranged in the ascending order of AOP as follows : Pd/AC (0.29) < Mn/AC (0.36) < AC (0.40) < Co/AC (0.49) < Fe/AC (0.51). However, the catalytic effects in the Co/AC and the Fe/AC processes were little in comparison with O3/AC process. The maximum concentrations of intermediates such as hydroquinone and catechol formed from the decomposition of phenol were arranged in the ascending order of AOP as follows: Pd/AC < Fe/AC < Co/AC < AC < Mn/AC. In the case of Pd/AC process, these intermediates were almost disappeared after an one hour of reaction.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.173-174
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• 2002

실내 공기질은 재실자의 건강과 쾌적성 뿐만 아니라, 생산성 및 작업능률에도 영향을 미치며, 산업화와 자동차의 증가로 인한 대기오염은, 실내 공기질에 악영향을 미치고 있다. 또한, 에너지 절약을 위한 건물의 밀폐화와 환기율의 감소로 실내공기오염에 대한 관심도 증가되고 있다. 이는 결국, 보다 체계적이고 실용적인 공기정화 시스템의 필요로 이어지며, 그런 의미에서 현재 많은 상용 공기청정기에 대한 보다 효과적인 평가가 필요하다. (중략)

• Journal of Korean Society of Environmental Engineers
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• v.36 no.5
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• pp.311-316
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• 2014

Effects of operating parameters such as activated carbon dose and pH on the phenol oxidation in ozone-activated carbon hybrid process were investigated through a kinetic study. Activated carbon enhanced the self-decomposition of ozone, generating $OH{\cdot}$, thus promoting phenol degradation. The pseudo-first order rate constants of phenol degradation increased and half-life of phenol decreased with activated carbon dose. The increase of pH enhanced $OH{\cdot}$ generation through chain reactions initiated by $OH^-$, therefore increasing the phenol degradation rate. TOC removal efficiency increased about 3.2 times by adding activated carbon in ozonation process.