• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.311-318
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• 2015

This work investigated the plasma treatment of aqueous bisphenol A (BPA) solution and mineralization pathways. For the effective contact between plasmatic gas and aqueous BPA solution, the plasma was created inside a porous ceramic tube, which was uniformly dispersed into the aqueous solution through micro-pores of the ceramic tube. Effects of the gas flow rate, applied voltage and treatment time on the decomposition of BPA were examined, and analyses using ultraviolet (UV) spectroscopy, ion chromatography and gas chromatography-mass spectrometry were also performed to elucidate mineralization mechanisms. The appropriate gas flow rate was around $1.0L\;min^{-1}$; when the gas flow rate was too high or too low, the BPA decomposition performance at a given electric power decreased. The increase in the voltage improves the BPA decomposition due to the increased electric power, but the energy required to remove BPA was similar, regardless of the voltage. Under the condition of $1.0L\;min^{-1}$ and 20.8 kV, BPA at an initial concentration of $10L\;min^{-1}$ (volume : 1 L) was successfully treated within 30 min. The intermediates produced by the attack of ozone and hydroxyl radicals on BPA were further oxidized to stable compounds such as acetate, formate and oxalate.

• Clean Technology
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• v.12 no.4
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• pp.250-258
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• 2006

CFC compounds such as CFC-113 and 1,1,1-TCE, etc. have been used in various industries due to their excellent chemical stability, thermodynamic characteristics, non-inflammability and anti-corrosiveness. However, in oder to protect the earth environment, "the Montreal Protocol on substances that deplete the ozone layer" was adopted in 1989 for prevention of production and utilization of these CFC compounds and alternative cleaning agent have been required in the industry. The objective of this study is to develop non-aqueous cleaning agents that do not require major change of cleaning system, have excellent cleaning efficiency, are favorable to the environment, are harmless to the human body, and are not generated corrosive materials. In this work, non-aqueous cleaning agents have been formulated with glycol ether series and paraffinic hydrocarbon series with siloxane, and their physical properties and cleaning efficiencies were analyzed and compared with those of regulated materials. As a result of physical properties measurement of the formulated cleaning agents, it is expected that they may have good penetration ability into contaminated materials due to their properties with low density and low surface tension. Measurement of flash point and vapor pressure of the cleaning agents will be helpful for evaluation of their safety and working environment. The experimental results of cleaning flux, solder and grease by the formulated cleaning agents show that their cleaning abilities of soils were good and that there were no residues on the substance after cleaning. Therefore, alternative cleaning agents which have equivalent cleaning ability to regulating materials, good penetration ability and low hazard to human body, have been developed in this work.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.1
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• pp.52-56
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• 1987

The antioxidative activity of each molecular weight (MW) fraction of Maillard reaction products prepared from a D-glucose and glycine system, i. e., MW below 1000, MW between 1000 to 3000 and MW above 5000, nondialyzable melanoidins, reduced melanoidins and ozone-treated melanoidins were estimated in a linoleic acid-aqueous system. The antioxidative activity ana reducing ability of Maillard reaction products increased with increasing molecular weight and color intensity. Maillard reaction products of MW above 1000 showed obvious antioxidative activity and reducing ability, whereas the MW fraction below 1000 showed only weak activities. When nondialyzable melanoidins were reduced with sodium borohydride, their color intensity and reducing ability remarkably decreased, but their antioxidative activity did not decrease so much.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.23-29
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• 2016

Ozonation was investigated for its ability to remove pyruvic acid in a laboratory-scale batch reactor under various experimental conditions, including UV irradiation, TiO₂ addition, and variations in temperature. An ozone flow rate of 1.0 L min^-1 and a concentration of 75±5 mg L^-1 were maintained throughout the experiment, and pH, COD, and TOC were measured at 10 min intervals during a 60 min reaction. Our results confirmed that the combination of UV irradiation and photocatalytic TiO₂ in the ozonation reaction improved the removal efficiency of both COD and TOC in aqueous solution at 20℃. Pseudo first-order rate constants and activation energies were quantified based on the COD and TOC measurements. We observed that the O₃/UV, O₃/UV/TiO₂ system increased mineralization and reduced the activation energy (E_a) necessary for pyruvic acid decomposition.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.731-738
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• 2011

In this study AOPs of $O_3/UV$ radiation, $O_3/Mg(OH)_2/UV$ radiation and $O_3/MgO/UV$ radiation system for phenol treatment in aqueous solution was performed in a laboratory scale circulating batch reacter. Flow rate of ozone 1.0 L/min, ozone concentrations $150{\pm}10mg/L$ was maintained constantly at the above-mentioned oxidation processes. During the oxidation processes the $COD_{Cr}$ and TOC was measured in the composition. The pseudo first-order rate constants of the processes was $5.12{\times}10^{-5}$, $1.19{\times}10^{-4}$ and $1.79{\times}10^{-4}sec^{-1}$, and the activation energy was 3.03, 1.79 and $2.32kcal{\cdot}mol^{-1}$ at $20^{\circ}C$, respectively. It was found that both $Mg(OH)_2$ and MgO had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, $O_3/MgO/UV$ system is an effective and feasible routes for catalytic ozonation of phenol in water.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.382-391
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• 2009

Atmospheric speciated mercury concentrations including total gaseous mercury (TGM) and reactive gaseous mercury (RGM) were measured in Chuncheon from March 2006 to November 2008. Average concentrations were 2.10 ${\pm}$ 1.50 ng/$m^3$ and 3.00 ${\pm}$ 3.14 pg/$m^3$ for TGM and RGM, respectively. RGM concentrations were higher during daytime than nighttime probably because of high photochemical activities. We found that RGM concentration considerably increased as ozone increased when fog occurred, indicating that ozone was the important oxidant for $Hg^0$ in aqueous phase. TGM concentration showed positive correlations with CO and $PM_{10}$ which can transport in long-range, but there was no correlation with $NO_2$. Considering that major source of mercury is combustion process, this result showed that local sources did not significantly impact on TGM concentration in Chuncheon. Five-day backward trajectories were calculated for the samples representing high and low concentrations of TGM, and determined that industrialized area of China including Shenyang and Beijing influenced TGM concentrations in Chuncheon.

• Clean Technology
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• v.11 no.3
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• pp.129-139
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• 2005

Fluoride-type cleaning agents such as TFEA (2,2,2-trifluoroethanol) and HFE (hydrofluoroether) are noticed to be next generation cleaning agents alternative to CFCs since they do not destruct ozones in the stratosphere due to no containment of chloride in the molecule, have lower global warming potential compared to HFCs and HCFCs, and are thermally stable compounds. Thus, the physical properties and cleaning agents were measured and compared with those of CFC-113, 1,1,1-TCE and HCFC-141b which are ozone destruction substances. They were also compared and evaluated with those of IPA and methanol which are currently employing as alternative cleaning agents. And TFEA-based cleaning agents consisted of TFEA and alcohols or HFEs were formulated, their physical properties and cleaning abilities were measured and their utilization as alternative cleaning agents was evaluated. As a result, TFEA and HFEs have lower cleaning ability for their removal of various soils compared to chloride-type cleaning agents, but theyshow excellent cleaning ability for Fluoride-type soils. And it is observed that the formulated cleaning agents of TFEA and alcohols or HFEs caused to increase cleaning ability of flux and unsoluble cutting oil more than 100% compared to their individual component. Therefore, the fluoride-type cleaning agents are expected to be utilized for development of environmental-friendly non aqueous cleaning agents with excellent cleaning ability if they are formulated with proper solvents or additives.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3039-3044
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• 2011

This study suggests the prediction model for the concentration variation of $NO_2{^-}$ and $NO_3{^-}$ along with the rate constants of all reactions during ozonation under UV radiation ($O_3$/UV process). While $NO_2{^-}$ was completely converted into $NO_3{^-}$ during the $O_3$-only process, the production of $NO_2$ radical or $N_2O_4$ was expected in the $O_3$/UV process. In addition, the quenching of OH radicals, by $NO_2$ radical in the $O_3$/UV process, resulted in regeneration of $NO_2{^-}$. However, the regeneration of $NO_2{^-}$ was not observed in the $O_3$/UV process in the presence of $C_6H_6$ where the concentrations of $NO_2{^-}$ and $NO_3{^-}$ were significantly reduced compared to in the process without $C_6H_6$. The pseudo-first order rate constants of all species were calculated with and without the presence of $C_6H_6$ to predict the variation of concentrations of all species during the $O_3$/UV process. It was suggested that $NO_2{^-}$ and $NO_3{^-}$ in the $O_3$/UV process can be more effectively removed from an aqueous system with an OH radical scavenger such as $C_6H_6$.

• Analytical Science and Technology
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• v.6 no.1
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• pp.65-75
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• 1993

A number of alternative cleaning solvents to CFC 113 which was identified as a ozone-depleting meterial were collected to measure their experimental physecal properties of density, surface tension, Refractive Index, boiling point, pH, viscosity, flash point, and soltbility. They might be classified as aqueous, simi-aqeous, alcohol ketone, and halogen cleaning solvents. The solubilities of abietic acid, a major component of flux used in PCB (Printed Circuit Board) of the electronic indystry, into the cleaning solvents including CFC 113 were determined for comparison. The assorted cleaning solvents have their own advantages and disadvantages. Therefore a end-user carefully needs to choose the best-fit cleaning solvent after the safety, stability, and economics as well as the effectiveness by physical properties of the alternative cleaning solvents are integratedly considered.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.767-773
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• 2010

In recent years, there has been considerable concern over the release of methyl tert-butyl ether (MTBE), a gasoline additive, into the aquifers used as potable water sources. MTBE readily dissolves in water and has entered the environment via gasoline spills and leaking storage tanks. In this study air stripping and ozonation of MTBE in aqueous solution were performed in a laboratory scale batch reacter. The mass transfer rate (N) was evaluated and a values about $1.24{\times}10^{-6}\;mol{\cdot}sec^{-1}$ was found. In the ozonation of MTBE a 8.3% decrease of the COD and a 6.5% decrease of the TOC lead to BOD/COD = 0.03. The peudo first-order rate constants of the ozonation of MTBE was $3.75{\times}10^{-5}\;sec^{-1}$. The resulting Ea of 4.80 kcal；mol-1 was observed for molecular ozone reactions.