• Korean Journal of Materials Research
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• v.26 no.8
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• pp.406-411
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• 2016

In order to reuse the photocatalyst and enhance the photolysis efficiency, we have used atmospheric pressure dielectric barrier discharge (APDBD) to clean and activate $TiO_2$ powder. The photocatalytic activity of the $TiO_2$ powder before and after APDBD treatment was evaluated by the degradation of methylene blue (MB) in aqueous solution. The apparent reaction rate constant of photolysis of the first sample of reused $TiO_2$ cleaned by APDBD improved to a level up to 0.32h-1 higher than the 30 % value of the initial $TiO_2$ powder. As the number of photolysis reactions and APDBD cleanings increased, the apparent rate constants gradually decreased; however, the fourth photolysis reaction still showed a value that was greater than 10% of the initial value. In addition, APDBD treatment enhanced the process by which $TiO_2$ effectively adsorbed MB at every photolysis stage.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.61-68
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• 2000

The use of photo-catalytic processes in pollution abatement and resource has a significant economic importance. Therefore, the applications of photochemical oxidation of secondary effluent driven by UV, TiO2, TiO2/UV, H2O2/UV and TiO2/H2O2/UV, have been investigated in order to treat the secondary effluent from municipal sewage. Various experimental parameters such as BOD, CODcr, Nurbidity, total P, and SPC were examined in each photo-catalytic reaction system. The results showed that the application of single oxidant such as UV, TiO2 only has a minor effect on parameters reduction (CODcr, BOD, etc) to treat the secondary effluent, whereas the combinations of oxidants increase the removal efficiency. The best removal efficiency in every parameters was achieved by the combination of TiO2, H2O2 and UV. It was also found that the optimum amount of TiO2 for the treatment was 1g/ι to achieve water reuse standard. From the results, the photocatalytic reaction system can be an alternative as a post-treatment to treat the secondary effluent from municipal sewage.

• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.2
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• pp.107-112
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• 2013

The ZnO is able to produce hydrogen from water however it can only absorb ultraviolet region due to its 3.37eV of wide band gap. Therefore efficiency of solar hydrogen production is low. In this work we report investigation results of improved visible light photo-catalytic properties of CdSe quantum dots(QDs) sensitized ZnO nanorod heterostructures. Hydrothermally vertically grown ZnO nanorod arrays on FTO glass were sensitized with CdSe by using SILAR(successive ionic layer adsorption and reaction) method. Morphology of grown ZnO and CdSe sensitized ZnO nanorods had been investigated by FE-SEM that shows length of $2.0{\mu}m$, diameter of 120~150nm nanorod respectively. Photocatalytic measurements revealed that heterostructured samples show improved photocurrent density under the visible light illumination. Improved visible light performance of the heterostructures is resulting from narrow band gap of the CdSe and its favorable conduction band positions relative to potentials of ZnO band and water redox reaction.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.699-704
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• 1999

The Photodegradation efficient of total organic compounds in the drinking water has been studied using the methods of photocatalytic reaction and laser beam irradation. The results are summarized as follows; 1. The photodegradation efficiency of total organic compounds shows as $50\%\;to\;80\%$ as within one hour and after this the efficiency is decreased slowly. 2. The photodegradation efficiency of total organic compounds shows as 65 to $90\%$ within 3.3min. when Nd : YAG beam is irradiated to the water layer. 3. An excellent observation of the organic compound removal efficiency gives revealed in that case of the longest wavelength of 532nm is irradiated among the three kinds of laser beam sources of 532nm, 355nm and 266nm. 4. The organic compound removal efficiency shows high in the case of UV beam irradiation in the thin layer of water. However the efficiency is not depended on the thickness of water layer severely. 5. The removal efficiency of the organic compounds in the direct irradiation shows higher than the indirect irradiation in the case of UV beam, but the efficiency is not depended on the direction of irradiation in the case of Nd : YAG beam irradiation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.153-154
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• 2018

As the air pollution progresses, the pollution degree of the indoor air quality is increased, and when the pollution degree of the indoor air quality is increased, it causes respiratory diseases and skin diseases. In addition, volatile organic compounds are released from the materials used for architectural interior decoration, and volatile organic compounds are the main cause of polluting indoor air quality. In order to improve indoor air quality, we tried to secure indoor air quality pollution by using photocatalyst which has the function of decomposing harmful substances. photocatalyst is a material that promotes chemical reaction by absorbing light. The photocatalyst used in the experiment was TiO₂, In this study, an adsorption type hardener for reducing volatile organic compounds was prepared by photocatalytic reaction. the formaldehyde and CO₂ concentrations of the cured products were analyzed according to the TiO₂ content.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.101-107
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• 1999

$TiO_2$ and $xTiO_2-ySiO_2$ system photocatalysts were developed by sol-gel method based on the change of production parameters, and their structure of crystallization and the specific surface area was measured. Considering the efficiency of the ethanol decomposition using the catalyst, the conclusion was made as follows: 1) By means of X-ray analysis of $TiO_2$ powder that is obtained from water and Titanium alkoxide with various molar ratios, it is shown that structure of crystallization is a dominating structure and, on the other hand, the crystallization of rutile also partly exists. The specific surface area is at its maximum value at R=6, which is the molar ratio of water vs. alkoxide, whereas its value goes down as the molar ratio increases. In the reaction of using $TiO_2$ catalyst, the ethanol is decomposed into the extent of 15 ~30% in an hour and three hours are necessitated for 70% decomposition. 2) $TiO_2/SiO_2$ powder is developed from Titanium and Silicon alkoxide by a hetero-condensation process. The increase of SiO$_2$ contents causes the decrease of the degree of crystallization of the gel, whereas the specific surface area preferentially increases. In the decomposition reaction of the ethanol, the decomposition efficiency represents 25~60% in an hour. It is, however, examined that the efficiency inactively increases corresponding to the duration of reaction time. It is shown that more than 90% of ethanol is decomposed when reaction time is about three hours and the efficiency illustrates the maximum value for 60-$TiO_2/4O-SiO_2$ catalyst.

• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.452-457
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• 2007

Titanium foil and mesh(anodized tubular $TiO_2$ electrode, ATTE) were anodized in a bath at $5^{\circ}C$ with 20V external bias applied, then annealed at different temperatures($450^{\circ}C{\sim}850^{\circ}C$) to obtain tubular $TiO_2$ on the Ti substrate. The prepared sample was used to investigate rate of hydrogen production as well as Cr(VI) reduction. The ATTEs annealed at relatively lower temperatures showed higher activity than those at relatively higher temperatures. In particular, the Cr(VI) reduction was pH-dependent. To improve photocatalytic Cr(VI) reduction with the ATTEs, two configurations, fixing foil type and rotating mesh type, were also compared. As a result, the rotating mesh type was much more effective for Cr(VI) reaction than the former due to the more efficient use of the light. In the rotating type reactor, as the rotating speed increased, the rate of the Cr(VI) reduction was getting faster.

• Rapid Communication in Photoscience
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• v.2 no.2
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• pp.42-45
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• 2013

Natural photosynthesis utilizes solar energy to convert carbon dioxide and water to energy-rich carbohydrates. Substantial use of sunlight to meet world energy demands requires energy storage in useful fuels via chemical bonds because sunlight is intermittent. Artificial photosynthesis research focuses the fundamental natural process to design solar energy conversion systems. Nicotinamide adenine dinucleotide ($NAD^+$) and $NADP^+$ are ubiquitous as electron transporters in biological systems. Enzymatic, chemical, and electrochemical methods have been reported for NADH regeneration. As photochemical systems, visible light-driven catalytic activity of NADH regeneration was carried out using platinum nanoparticles, molecular rhodium and cobalt complexes in the presence of triethanolamine as a sacrificial electron donor. Pt nanoparticles showed photochemical NADH regeneration activity without additional visible light collector molecules, demonstrating that both photoactivating and catalytic activities exist together in Pt nanoparticles. The NADH regeneration of the Pt nanoparticle system was not interfered with the reduction of $O_2$. Molecular cobalt complexes containing dimethylglyoxime ligands also transfer their hydrides to $NAD^+$ with photoactivation of eosin Y in the presence of TEOA. In this photocatalytic reaction, the $NAD^+$ reduction process competed with a proton reduction.