• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.1006-1015
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• 2005

We investigated the effect of hydroxyl radicals on the photolysis of triclosan (TCS), which is a potent broad-spectrum antimicrobial agent. TCS degradation during the initial reaction time of 5 min followed a pseudo-first order kinetic model ai all light intensities at a wavelength of 365 nm and at the low light intensities at a wavelength of 254 nm. The photodegradation rate significantly increased with decreasing wavelength and increasing the UV intensities. The activity of hydroxyl radicals was suppressed when methanol was used as the solvent instead of water. An increase in the photon effect was observed when the UV intensity was higher than $5.77{\times}10^{-5}$ einstein $L^{-1}min^{-1}$ at 254 nm, and lower than $1.56{\times}10^{-4}$ einstein $L^{-1}min^{-1}$ at 365 nm. The quantum yield efficiency for the photolysis of TCS was higher at 365 nm than at 254 nm among the above mentioned UV intensities. Dibenzodichloro-p-dioxin (DCDD) and dibenzo-p-dioxin were detected as intermediates at both UV intensities of $1.37{\times}10^{-4}$ and $1.56{\times}10^{-4}$ einstein $L^{-1}min^{-1}$ at 365 nm. Dichlorophenol and phenol were also detected in all cases. Based on our findings, we presented a possible mechanism of TCS photolysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6952-6957
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• 2014

In photocatalysis, the addition of metal matter to $TiO_2$ can alter the surface properties. As such, the metal can increase the rate of the photodegradation reaction. In this study, a range of modified $TiO_2$ photocatalysts were prepared and tested to improve the activity of photodegradation at a batch-typed photoreactor. To obtain a good sol solution of the $TiO_2$ photocatalyst, several types of dispersion agents and stabilizers were investigated. The photocatalyst solutions were modified with isoproply alcohol as the dispersion agent and sodium silicate as the stabilizer. The effects of various metallic elements on enhancing the photocatalytic activity of $TiO_2$ on the degradation of toluene were examined. Palladium-added $TiO_2$ was found to be the best, whereas copper or tungsten-added also showed good results. In the case of palladium addition, the increase in removal efficiency was 25%. On the other hand, Fe-added $TiO_2$ showed a notable decrease in photocatalytic degradation. Additional doping of copper or tungsten on the $Pd/TiO_2$ had no positive effect on the photodegradation activity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.57-62
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• 2000

The photocatalytic degradation of trichloroethylene(TCE) in water on various types of$TiO_2$ was studied. Surface properties of $TiO_2$were characterized by XRD, SEM, and BET in our previous work(23) . $TiO_2$from Aldrich has 100$\%$pure anatase, TiO$_2$from KIER has 100$\%$ pure rutile structure, and P25-TiO$_2$from Degussa has mixed structure of anatase(75$\%$) and rutile(25$\%$) . Firstly, optimum conditions for TCE degradation were examined in this study. Results showed that optimum loading amount of catalyst was 0.1 wt% and recirculation flow rate of mixture(distilled water and TCE) was 200 cc/min. Secondly, the effect of $TiO_2$structure on TCE degradation was examined. Results revealed that anatase structure generally has better photocatalytic activity than rutile structure. Especially, mixed structure(Degussa P25-$TiO_2$) has the highest activity due to small particle size and large specific surface area.

• Clean Technology
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• v.21 no.3
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• pp.178-183
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• 2015

Lead molybdate (PbMoO₄) oxides were successfully synthesized using a conventional hydrothermal method and a microwave-assisted hydrothermal method. They were characterized by XRD, DRS, BET, Raman, SEM and PL. We also investigated the photocatalytic activity of these materials for the decomposition of Rhodamine B under UV-light irradiation. From XRD and Raman results, well-crystallized PbMoO₄ crystals have been successfully synthesized regardless of preparation method and had 42~59 nm particle size. The PbMoO₄ catalysts prepared using microwave-assisted process had the similar particle size and enhanced the photocatalytic activity when compared to that prepared by hydrothermal method. The PbMoO₄ catalysts prepared under the irradiation of microwave for 75 min showed the highest photocatalytic activity. The PL peaks appears at about 530 nm at all catalysts and it was also shown that the excitonic PL signal is proportional to the photocatalytic activity for the decomposition of Rhodamine B.

• Membrane Journal
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• v.4 no.3
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• pp.152-162
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• 1994

The photodegradation efficiency of formic acid on $TiO_2$ photocatalytic membranes was investigated. A new titania membrane reactors for purification of water combining microfiltration with photocatalytic degradation of organic compounds were developed. Titania membrane tubes(average pore size of $0.2\mu m$) were prepared by the slip casting, and porous thin films of $TiO_2$ were formed on the tube surface by the sol-gel process to increase the surface area, and consequently to increase photodegradation efficiency of organic compounds. The UV light with the wavelength of 365 nm was used as a light source for photocatalytic reactions. The photodegradation efficiency of the organic compounds was strongly dependent on the flux of the solution, the microstructure of the membrane (sol pH), and the amount of $O_2$ supplied. The effects of the primary oxidant such as $H_2O_2$ and dopants such as $Nb_2O_5$ on the photodegradation efficiency were also investigated. The results showed that more than 80% of formic acid could be degraded using membrane coated with a $TiO_2$ sol of pH 1.45. The photodegradation efficiency could be improved by about 20% when adding $H_2O_2$ in feed solution or doping $TiO_2$ membranes with $Fe_2O_3$.

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.300-301
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• 2005

• Clean Technology
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• v.16 no.1
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• pp.46-50
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• 2010

This study focuses on the removal of water-suspended toluene of a representative sick house compounds in a liquid photo-system using nanometer-sized Sn-incorporated $TiO_2$ which was synthesized by a solvothermal method. The characteristics of the synthesized Sn-$TiO_2$ were analyzed by X-ray Diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and UV-visible spectroscopy (UV-Vis). To estimate the photocatalytic activity of Sn-$TiO_2$, the photodegradation of water-suspended toluene was performed, and the remaining concentration was determined using UV-visible spectroscopy. The water-suspended toluene photodegradation over Sn-incorporated $TiO_2$ catalyst was better than that over pure $TiO_2$ (anatase). The water-suspended toluene of 500 ppm was perfectly decomposed within 300 minutes over 0.01 mol% Sn-$TiO_2$.

• Membrane Journal
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• v.17 no.3
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• pp.244-253
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• 2007

This research investigated the effect of a photocatalytic reaction on nanofiltration(NF) membrane fouling by natural organic matter(NOM). The photocatalytic degradation was very effective for destruction and transformation of NOM and was carried out by titanium dioxide($TiO_2$) and $TiO_2$-immobilized bead as a photocatalyst. In order to compare their phtocatalytic properties, the photocatalytic degradation of humic acid in the presence of calcium ion was used as a model reaction. After the photocatalytic degradation the membrane fouling was dramatically decreased.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.757-764
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• 1993

The photochemical precursors, 1,1,1,3,3,3-hexamethyl-2-phenyltrisilane(2) and 2,3-dicarbomethoxy-1,4,5,6,7-pentaphenyl-7-silanorbornadiene(5) were synthesized in the yield of 10% and 73%, respectively. Irradiation of 2 at 254 nm in the presence of triethylsilane gave 1,1,1-triethyl-2-phenyldisilane (6) in 44% yield which was the product of phenylsilylene insertion into the Si-H bond. Irradiation of 2 in the presence of diphenylacetylene gave 1-phenyl-1-silacyclopenta-2,4-diene(4) in 68% yield together with 1,2-diphenyl-1,2-disilacyclohexa-2,5-diene(26%) which were formed from [2＋2] addition of the silacyclopropene to diphenylacethylene and formed from dimerization of silacyclopropene, respectively. From the neat photolysis of precursor 2,1,5-dihydrosilanthrene(11), intermolecular C-H insertion product of phenylsilylene and 1,2-diphenyltrisilane(12), Si-H insertion product of phenylsilylene to the precursor were obtained in the yield of 5% and 7%, respectively. In the same experimental condition, both photolyses of 5 in the presence of triethylsilane and methanol showed that the intramolecular 1,5-sigmatropic rearrangement of precursor 5 to give the formation of silylenolether was more favorable process than the generation of phenylsilylene.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.388-389
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• 2003

Nitrous acid는 태양광선의 존재 하에 광분해 되어 히드록실 라디칼(hydroxyl radical, OH)을 발생시키는 대류권 오존생성 원인 물질이다. 대기화학에 있어서 Nitrous acid의 중요성을 보면, 야간에 농도가 증가된 Nitrous acid는 태양광이 존재하는 아침부터 광분해 (<390nm)로 히드록실 라디칼을 생성하여 오존생성반응을 일어나게 하는 것으로 대기 중 오존의 생성에 중요한 역할을 한다. 반면에 Nitric acid는 reactive nitrogen compounds(즉 NO, NO$_2$ 그리고 $N_2$O$_{5}$)의 주된 최종 생성물질이다. (중략)