• Journal of Korean Society for Atmospheric Environment
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• v.33 no.2
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• pp.87-96
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• 2017

In this study, 4 gases containing typical chlorinated volatile organic compounds (VOCs) were treated by ultraviolet (UV) irradiation. The typical chlorinated VOCs are dichloromethane (DCM), trichloromethane (TCM), carbon tetrachloride (CTC) and trichloroethylene (TCE). The removal efficiency (RE) and the products of chlorinated VOCs by UV irradiation are investigated. At this time, 2 types of background gas (air and nitrogen) were used to figure out the RE by photooxidation and photolysis. The specification of UV-lamp used in this study was low-pressure mercury lamp emitting wavelength of 185~254 nm. The experimental conditions were set as initial VOC concentration of $180{\pm}10ppm$, empty bed retention time (EBRT) of 53 s, temperature of $23{\pm}2^{\circ}C$ and relative humidity of $65{\pm}5%$. In the photolysis condition with nitrogen ($N_2$) as background gas, the averaged RE of the 4 types of chlorinated VOCs was about 24% higher than that with photooxidation; and the REs of VOCs except CTC were confirmed as >99%. The composition of off-gases after UV photooxidation in air was investigated and several intermediates from DCM, TCM and TCE were detected by GC/MS. Among them, phosgene which is a toxics was detected as an intermediate of TCM. In addition, the concentration of carbon dioxide ($CO_2$) in the off-gases was measured to calculate the mineralization rate (MR). With the photooxidation, TCE showed the highest RE (>99%) while MR was the lowest (17%); and the MR of DCM was the highest (86%). In addition, particulate matters (PM) in the off-gases was also detected and high concentrated $PM_{10}$ ($21,580{\mu}g{\cdot}m^{-3}$) and $PM_{2.5}$ ($6,346{\mu}g{\cdot}m^{-3}$) were detected in TCE off-gas. More than 99% of the chlorinated VOCs could be removed using UV254-185 nm lamp, while it is necessary to conduct further studies on the production and treatment of secondary pollutants.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.255-256
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• 2000

휘발성 유기화합물(Volatile Organic Compounds : VOCs)은 각종 산업체에서 많이 사용되고 있는 용매와 화학 및 제약공장 플라스틱의 건조공정에서 배출되는 유기가스 등까지 매우 다양하며, 저비점 액체연료, 파라핀, 올레핀, 방향족 화합물등 우리 생활주변에서 흔하게 사용되는 탄화수소류들이 거의 VOCs이다. 이러한 VOCs를 제어하기 위하여 폭넓은 제어기술의 연구 및 개발이 진행되고 있다. (중략)

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.798-802
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• 1996

The photochemical decomposition of aqueous ammonia in the absence (saturated with argon) and the presence of O2 (saturated with air or oxygen) has been investigated using 184.9 nm UV light. The decomposition of ammonia depended on the concentration of oxygen in the solution. With increasing the concentration of oxygen, the decomposition of ammonia diminishes. Hydrazine is found the major product from the irradiation. In the presence of oxygen, hydrogenperoxide was also produced. The product yields depended also on the concentration of oxygen in the solution. The initial quantum yield of the products and of the ammonia decomposed were determined. Probable reaction mechanisms for the reaction were presented from the products analysis.

• Korean Journal of Environmental Agriculture
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• v.21 no.3
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• pp.172-177
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• 2002

Photodegadation rates of carbofuran in aqueous solution were measured under various test conditions mainly following the guidelines of U.S. EPA and OECD. Half-lives of carbofuran in distilled water were 9.7 days. 3.3 days, and 1 hr under natural sunlight, SUNTEST with UV filter, and SUNTEST without UV filter, respectively. Waters from a paddy field accelerated the decomposition by factor of 6. It was confirmed that the use of SUNTEST could shorten the test period of photodegradation.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.392-400
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• 2004

This research uses the $TiO_2$/UV process to verify the most suitable condition and possibility to dispose dyeing wastewater that contains pigment and a large amount of pollutants. For this, this research has enforced experiments that compare photo adsorption, photolysis, and photo catalyst oxidation reaction, and also evaluated and analyzed the change of pH and $TiO_2$ dosage, irradiation rates of ultraviolet rays and the dosage change and injection method of $H_2O_2$. According to the results of the dyeing wastewater experiment of storehouse catalyst that uses the new form of $TiO_2$, the photo catalyst oxidation reaction proved to be more effective than photo adsorption and photolysis; 35%, 21% in the case of $TCOD_{cr}$ and 39%, 28% in the case of chromaticity. Taking into consideration the reaction time, amount of photo catalyst reaction and irradiation amount of ultraviolet rays, the decomposition efficiency of pH change proved to be most effective at pH 4. On the whole, the acidity area proved to be effective in dyeing water exclusion than neutral and alkalinity areas. Having evaluated the influence of $TiO_2$ dosage, not only does the decomposition efficiency continuously improve as the $TiO_2$ dosage increases but the shielding effect does not occur also when the $TiO_2$ is at a fixed state. The influence of ultraviolet irradiation amount concluded in the result that as the ultraviolet irradiation amount increases the decomposition efficiency continually increased, but in the case of chromaticity when the irradiation amount was higher than 37.8mW/cm2 the removal efficiency is slowed remarkably. The influence of $H_2O_2$ dosage evaluation reached the results that although the decomposition efficiency increases with the increase of $H_2O_2$ dosage, when above 150mg (total dosage: 1200mg) $H_2O_2$ consumes OH radical itself and reduces the decomposition efficiency. Also in the case of the $H_2O_2$ injection method rather than injecting in the whole amount of $H_2O_2$ (1200mg) needed at the beginning all at once, injecting divided quantities of $H_2O_2$ whenever the electric current density falls below 10mgfl reduces the wases of OH radical due to an excess of $H_2O_2$ and in tum heightens the decomposition efficiency.

• Clean Technology
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• v.23 no.3
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• pp.294-301
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• 2017

Air pollution associated with the $NO_x$ emission from the ship engines is becoming one of the major environmental concerns these days. As the regulations on ship pollutants are strengthened, the wet absorption method, for controlling complex pollutants in a confined space, has the advantage of simultaneously removing various pollutants, but the low solubility of nitrogen monoxide is drawback. In this study, for improving existing denitrification scrubber system, NO oxidation process by hydroxyl radical produced from irradiating UV light on $H_2O_2$ is suggested and the $H_2O_2$ decomposition rates and hydroxyl radical quantum yields were measured to find the optimum condition of $H_2O_2$ photolysis reaction. As a result, the optimum quantum yield and photolysis rate of $H_2O_2$ were 0.8798, $0.6mol\;h^{-1}$ at 8 W, 2 M condition, and oxidation efficiency of 1000 ppm NO gas was 40%. In batch system, NO removal efficiency has a range of 65.0 ~ 67.3% according to input gas concentration of 100 ~ 1500 ppm. This results indicate that the scrubber system using hydrogen peroxide photolysis can be applied as air pollution prevention facility of ship engines.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.135-140
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• 2014

A bent-shape triazolyl derivative was synthesized via click chemistry, and its photophysical property was investigated in various solvents. In contrast to the invisible ultraviolet emission of other solutions, the chloroform solution exhibited a blue light emission at 460 nm. Furthermore, the blue fluorescence intensified as the UV exposure time at 365 nm increased. On the basis of $^1H$-NMR, pH paper, and acid-addition studies, we confirmed that chloroform was decomposed into HCl with the aid of the triazolyl derivative. The density functional theory calculations suggested that the eye-detectable blue fluorescence was attributed to an intramolecular charge transfer process of the protonated triazolyl derivative in the chloroform solution.

• Journal of Photoscience
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• v.9 no.3
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• pp.57-63
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• 2002

A homopolymer containing anthracene groups, poly[6-(9-anthryloxy)hexyl methacrylate] (PAn) was prepared and the effect of oxygen on its photochemical reaction was studied by UV and IR absorption spectroscopy in order to understand its photochemical behavior. Photochemical reaction of the PAn in THF solution under an atmosphere of air resulted in the formation of endoperoxide at the beginning stage of reaction followed by photodimerization reaction after all the oxygen was consumed, whereas photodimerization and endoperoxide formation took place concomitantly in the film state. The photoreversible reaction of the anthracene photodimer groups in the polymer by photolysis with 254 nm UV light was not efficient. The IR absorption spectral changes of the PAn film upon irradiation indicate that various photooxidation products were produced in the atmosphere of air.

• Mass Spectrometry Letters
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• v.12 no.3
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• pp.118-124
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• 2021

Many previous studies have focused on revealing the harmfulness of microplastic particles, whereas very few studies have focused on the effects of chemicals, particularly photooxidation product. In this study, products of photodegradation from expanded polystyrene (EPS), compounds produced by photolysis by ultraviolet (UV) light, were investigated. EPS was directly irradiated and photolyzed using a UV lamp, and then the extracted sample was analyzed using high-resolution mass spectrometry (HRMS). Multiple ionization techniques, including electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization, were used. In total, >300 compounds were observed, among which polystyrene monomer, dimer, and oxidized products were observed. In this work, the data presented clearly demonstrate that it is necessary to identify and monitor oxidized plastic compounds and assess their effect on the environment.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.245-251
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• 2017

In this study, ZnO, which is widely known as a non $TiO_2$ photocatalyst, was synthesized using coprecipitation method and Ag was added in order to improve the catalytic performance. The physicochemical characteristics of the synthesized ZnO and Ag/ZnO particles were checked using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL), and photocurrent measurements. The performance of catalysts was tested by $H_2$ production using the photolysis of $H_2O$ with MeOH. By adding Ag which plays a role as an electron capture on the ZnO catalyst, the performance increased due to the recombination of excited electrons and holes. In particular, $8.60{\mu}mol\;g^{-1}$ $H_2$ was produced after 10 h reaction over the 0.50 mol% Ag/ZnO.