• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.177-188
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• 2010

The use of an activated carbon (AC) system alone has the limitation that the pollutants are not eliminated but only transferred to another phase with the consumed AC becoming hazardous waste itself. Therefore, the present study investigated the feasibility of using a combined system of granular AC (GAC) with S-doped visible-light-induced $TiO_2$ (GAC/S-doped $TiO_2$) to clean monocyclic aromatic hydrocarbons (MAHs) with concentrations at $\leq$ 3 mg $m^{-3}$, using a continuous air-flow reactor. This study conducted three different experiments: an adsorption test of pure GAC and GAC/S-doped $TiO_2$; a long-term adsorptional photocatalytic (AP) activity test of GAC/S-doped $TiO_2$; and an AP activity test of GAC/S-doped $TiO_2$ under different conditions. For the AP activity test, three parameters were evaluated: various weights of GAC/S-doped $TiO_2$ (0.9, 4.4, and 8.9 g); various flow rates (FRs) (0.5, 1 and 2 L $min^{-1}$); and various input concentrations (ICs) of the target MAHs (0.1, 1, 2 and 3 mg $m^{-3}$). The adsorption efficiencies were similar for the pure GAC and GAC/S-doped $TiO_2$ reactors, suggesting that S-doped $TiO_2$ particles on GAC surfaces do not significantly interfere with the adsorption capacity of GAC. Benzene exhibited a clear AP activity, whereas no other target MAHs did. In most cases, the AP efficiencies for the target MAHs did not significantly vary with an increase in weight, thereby suggesting that, under the weight range tested in this study, the weights or FRs are not important parameters for AP efficiency. However, ICs did influence the AP efficiencies.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.286-291
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• 2001

As part of fundamental studies on the degradation of the organic compounds in industrial waste water, the photocatalytic degradation properties of the organic compound by means of the UV/TiO$_2$degradation process have been investigated. The test organic compound of acetic acid was chosen in this study. The testing of photo catalytic degradation were performed under various operation conditions such as TiO$_2$dosages, initial concentration of the organic, the aqueous pH's, etc. The effects of various parameters on the short time activity of the present acetic acid-UV/TiO$_2$system could be demonstrated from this investigation.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2637-2642
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• 2009

In this present paper, we prepared $MWCNT/TiO_2$ composites by using pre-oxidized multi-walled carbon nanotubes (MWCNTs) with different titanium alkoxide precursors in benzene solvent. The composites were comprehensively characterized by BET surface area, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and UV-Vis absorption spectroscopy. The photoactivity of the prepared materials, under UV irradiation, was tested using methylene blue (MB) in aqueous solution. Finally, according to the results of MB removal experiment, it can be considered that the MB degradation infect mainly caused by photocatalytic effect of $TiO_2$. Furthermore, the bactericidal test of the composites was also determined. It was indicated that $MWCNT/TiO_2$ composites with sunlight had greater effectiveness for B. cereus, S. aureus and E. coli than any other experimental conditions.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.439-444
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• 2012

To compare the photocatalytic performances of titania for purification of waste water according to applied voltages and doping, $TiO_2$ films were prepared in a 1.0 M $H_2SO_4$ solution containing $NH_4F$ at different anodic voltages. Chemical bonding states of F-N-codoped $TiO_2$ were analyzed using surface X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the co-doped $TiO_2$ films was analyzed by the degradation of aniline blue solution. Nanotubes were formed with thicknesses of 200-300 nm for the films anodized at 30 V, but porous morphology was generated with pores of 1-2 ${\mu}m$ for the $TiO_2$ anodized at 180 V. The phenomenon of spark discharge was initiated at about 98 V due to the breakdown of the oxide films in both solutions. XPS analysis revealed the spectra of F1s at 684.3 eV and N1s at 399.8 eV for the $TiO_2$ anodized in the $H_2SO_4-NH_4F$ solution at 180 V, suggesting the incorporation of F and N species during anodization. Dye removal rates for the pure $TiO_2$ anodized at 30 V and 180 V were found to be 14.0% and 38.9%, respectively, in the photocatalytic degradation test of the aniline blue solution for 200 min irradiation; the rates for the F-N-codoped $TiO_2$ anodized at 30 V and 180 V were found to be 21.2% and 65.6%, respectively. From the results of diffuse reflectance absorption spectroscopy (DRS), it was found that the absorption edge of the F-N-codoped $TiO_2$ films shifted toward the visible light region up to 412 nm, indicating that the photocatalytic activity of $TiO_2$ is improved by appropriate doping of F and N by the addition of $NH_4F$.

• Journal of Powder Materials
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• v.25 no.4
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• pp.316-321
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• 2018

Composites of P25 $TiO_2$ and hexagonal $WO_3$ nanorods are synthesized through ball-milling in order to study photocatalytic properties. Various composites of $TiO_2/WO_3$ are prepared by controlling the weight percentages (wt%) of $WO_3$, in the range of 1-30 wt%, and milling time to investigate the effects of the composition ratio on the photocatalytic properties. Scanning electron microscopy, x-ray diffraction, and transmission electron microscopy are performed to characterize the structure, shape and size of the synthesized composites of $TiO_2/WO_3$. Methylene blue is used as a test dye to analyze the photocatalytic properties of the synthesized composite material. The photocatalytic activity shows that the decomposition efficiency of the dye due to the photocatalytic effect is the highest in the $TiO_2/WO_3$ (3 wt%) composite, and the catalytic efficiency decreases sharply when the amount of $WO_3$ is further increased. As the amount of $WO_3$ added increases, dye-removal by adsorption occurs during centrifugation, instead of the decomposition of dyes by photocatalysts. Finally, $TiO_2/WO_3$ (3 wt%) composites are synthesized with various milling times. Experimental results show that the milling time has the best catalytic efficiency at 30 min, after which it gradually decreases. There is no significant change after 1 hour.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.650-653
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• 2007

$SnO_2$-doped $TiO_2$ powder was obtained from tin (IV) bis(acetylacetonate) dichloride and titanium diisopropoxide bis(acetylacetonate) with quinacridone as the dye sensitizer molecule. The structural changes of the reaction mixture were monitored by fourier transform infrared (FT-IR) spectroscopy. The morphology and microstructure of gel powder were studied by field-emission scanning electron microscopy (FE-SEM) and X-ray diffractometry (XRD). The photocatalytic activity of these powders with the anatase structure was investigated by using indigo carmine solution as a test dye

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.174-175
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• 2019

Recently, due to air pollution caused by fine dust, it is considered as a social problem. Increasing fine dust has intensified air pollution, causing many diseases and damages. This year, Seoul, South Korea, reached a severe level of fine dust pollution worldwide. The Ministry of Environment has strengthened the environmental standard for fine dust (PM2.5) from $50{\mu}g/m^3$ to $35{\mu}g/m^3$ since March 2018. When fine dust enters the human body, it causes bronchial or skin elongation such as respiratory allergies, irritable pneumonia, asthma and atopy. In this study, $TiO_2$ rutile with photocatalytic activity was used, and materials prepared by rutile sulfuric acid method were used. The photocatalytic activity rate is 95% or more and the density is $4.1g/cm^3$. The matrix was based on cement, and the substitution rate of $TiO_2$ was 0, 5, 10, 15, 20 (%). The test item is flexural strength and compressive strength.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.451-464
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• 2006

The purpose of this study was to search for an appropriate method of coating $TiO_2$ on orthodontic appliances. $TiO_2$ thin films were deposited on orthodontic wires and brackets using sol-gel, CVD (Chemical Vapor Deposition) and PE-CVD (Plasma Enhanced-CVD) methods. The roughness of $TiO_2$-coated surfaces was investigated via scanning electron microscope (SEM) and adhesive strength of $TiO_2$ thin films was measured by adhesive tape pull test. Methylene blue degradation test was carried out to evaluate the photocatalytic activity of $TiO_2$ and the corrosion resistance of $TiO_2$ thin films against fluoride solution was also analyzed by observing the surfaces of $TiO_2$-coated wires and brackets via SEM after immersion in sodium fluoride solution. Through the comparison of properties and photocatalytic activity of $TiO_2$ thin films according to the coating methods, the following results were obtained. Smoother surfaces of $TiO_2$ thin films were generated by CVD or PE-CVD methods than through the sol-gel method or the control. Adhesive strength of the $TiO_2$ thin films was highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Photocatalytic activity of $TiO_2$ thin films on methylene blue was the highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Corrosion resistance of $TiO_2$ thin films against fluoride solution was stronger in CVD and PE-CVD methods than in the sol-gel method. The results of this study suggest that the CVD or PE-CVD methods is more appropriate than the sol-gel method for $TiO_2$ coating on orthodontic wires and brackets.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.349-356
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• 2017

OH radical generation is one of the common method to evaluate photocatalytic activity. In many of previous studies, only the UV(Ultraviolet) light was applied to test photocatalytic ability of $TiO_2$ nanotubes by studying probe compound(4-Chlorobenzoic acid) concentration change in solution. Also, $TiO_2$ nanotubes were found to show some electrochemical characteristics when the flow of electric current was applied. In this study, the flow of electric current and UV light were applied at the same time to determine whether electrochemical characteristics of $TiO_2$ nanotube plate can give synergetic effect on the photocatalytic activity. $TiO_2$ nanotube was grown on Ti by anodic oxidation to create $TiO_2$ nanotube plate which can be used as a photocatalyst and a electrode that can undergo AOP(Advanced Oxidation Process) for water treatment. Probe compound solution was prepared using 4-chlorobenzoic acid and $H_2O$ as a solvent. NaCl was added to give conductivity to work as electrolyte. As a result, enough level of electric current flow was found to give synergetic photocatalytic effect which can be used for efficient AOP water treatment method.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.239-243
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• 2018

Up to now, microstructure changes of photocatalysts have been studied to improve photocatalytic activity. Especially, to improve the adsorption of reactants and reactive sites, porous and fine crystal structures have received much attention because of their large specific surface area. In this study, $TiO_2$ nanotubes were synthesized by hydrothermal method using $TiO_2$ nanoparticles; nanotubes were evaluated by oxidized methylene blue reduction test. Using synthesized $TiO_2$ nanotubes, results of TEM showed that the $TiO_2$ nanoparticles were changed into folding sheets and nanotubes. XRD results showed that the peaks of the nanoparticles almost disappeared and only the rutile (110) and anatase (200) peaks were observed. Comparison of photocatalytic properties of nanoparticles and nanotube structures was performed by measuring the UV-vis absorbance with reducing oxidized methylene blue. As a result, the reduction rate of nanotubes was found to be $0.24{\mu}mol/s$, which was 2.6 times higher than the rate of reduction of nanoparticles.