• Korean Journal of Materials Research
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• v.15 no.8
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• pp.508-513
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• 2005

[ $TiO_2-Fe_2O_3$ ] nanocomposite powders for magnetic photocatalyst were synthesized by sol-gel process, in which $TiO_2$ photocatalytic layer was formed on the surface of $\gamma-Fe_2O_3$ magnetic core. Transmission electron microscopy (TEM) observation and X-ray diffractometry (XRD) analysis revealed that$\gamma-Fe_2O_3$ nanoparticles, $10\~20nm$ in diameter, were coated by $TiO_2$ shell of 5nm in thickness and $TiO_2$ was anatase phase. Also hydroxyl group (-OH) used to decompose organic compounds was detected by Fourier transformation infrared spectrometry(FT-IR) analysis. UV-Visible spectrophotometry results showed that light absorption occurred in the wavelength range of $400\~700 nm$, and the band gap energy $(E_g)$ of powder was 1.8 eV. Finally it was found that the coercivity $(H({ci})$ and saturation magnetization $(M_s)$ of the powder were 79 Oe and 14.8 emu/g, respectively as experimental vibrating sample magnetometer (VSM) measurements.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.649-653
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• 2010

In this study, the variation of characteristics of P-25 photocatalyst with calcination temperature(Pure: non-thermally treated, 450, 650, $850^{\circ}C$) was studied. The photocatalysts were used as working materials for dye-sensitized solar cells: DSSCs) later on and their photovoltaic characterization was carried out. The photocatalytic degradation of methylene blue using the P-25 photocatalyst with different calcination temperature was almost same expect for $850^{\circ}C$. The solar energy conversion efficiency ($\eta$) of DSSCs prepared by the nanoparticles (photocatalyst) reached 6.9% (for pure), 6.5%(for 450), 5.8%(for 650) and 5.6%(850).

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.459-469
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• 2019

The ozonation of sulfamethoxazole (SMX) was performed at 20℃ using a pilot scale countercurrent bubble column reactor. Ozonation systems were combined with UV irradiation and TiO₂ addition. As the oxidation reaction proceeded in each treatment system, the pH of the sample decreased and in the O₃/UV/TiO₂ system, the pH change was the largest from 4.54 to 2.02. Under these experimental conditions, the scavenger impact of carbonate is negligible. The highest COD and TOC removal rate was observed in the O₃/UV/TiO₂ system due to the UV irradiation and the photocatalytic effect of TiO₂. Also, the highest mineralization ratio(ε) value is 0.2 in the O₃/UV/TiO₂ system, which means theoxidation capacity of the systems. The highest SMX degradation rate constants calculated by COD and TOC values (COD and TOC) were 2.15 × 10^-4 sec^-1 and 1.00 × 10^-4 sec^-1 in the O₃/UV/TiO₂ system, respectively. The activation energy (E_a) of ozone treatment follows the Arrhenius law. It was calculated based on _COD and _TOC. Each activation energy decreased in order of single O₃> O₃/TiO₂> O₃/UV > O₃/UV/TiO₂ system. The result showed that ΔH^≠ is more effective than ΔS^≠ in each SMX ozontaionsystem, that is characteristic of the common oxidation reaction.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.433-438
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• 2016

The current study evaluated the air quality of the smoking booth equipped with the air purification system consisting of photocatalysts and air filters by measuring the concentrations of hazardous substances of tobacco smoke such as CO, HCHO, $CH_3CHO$, PM10 and PM2.5. To enhance the removal efficiency of hazardous substances, an infrared ray was exposed to improve the reactivity of OH radical generated from the photocatalyst toward environmental tobacco smoke (ETS) gas phase hazardous materials. It was found that the smoking booth with the air purification system improved the removal efficiency of hazardous substances containing formaldehyde by 85.2% compared to that of the smoking booth without any purification systems. In addition, the removal efficiency of the fine dust after treatment was enhanced up to 89.4%.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.471-475
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• 2004

TiO$_2$, SiO$_2$, and PBA(Pseudo Boehemite Alumina) sol were prepared by sol-gel process. The particle sizes of these sol exhibited uniform 10∼30 nm. As the amount of SiO$_2$ sol increased, the temperature of phase transition (from anatase phase to rutile phase) was raised temperature than $600^{\circ}C$, which attributed to the enhanced photocatalyst properties. Also, the anatase phase was obtained with very small amount of the rutile phase from the addition of SiO$_2$ (10∼30 wt%) at annealing temperature of 120$0^{\circ}C$. The specimen with 20 wt% SiO$_2$ sol exhibited the maximum photocatalyst properties. But, the specimen with PBA sol did not affect photocatalytic activity due to the presence of rutile phase.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.697-705
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• 2011

The aim of this study was to examine ozonation disinfection efficiency for Escherichia coli DH5alpha removal, containing the multi-resistance plasmid pB10 as well as chlorination disinfection efficiency. In addition, plasmid pB10 removal rates were estimated by ozonation and chlorination. The removal efficiency of pB10 via ozonation was about 2 to 4 times higher than chlorination. High removal efficiency of pB10 is likely due to OH radical produced during ozonation. These results suggest that integration of advanced oxidation process such as ozonation (or photocatalytic oxidation) with conventional disinfection such as chlorination may be needed for effective control of antibiotic resistant bacteria and genetic materials.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.677-688
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• 2006

Currently, the application of $TiO_2$ photocatalyst has been focused on purification and treatment of wastewater. However, the use of conventional $TiO_2$ slurry photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we studied that solar light/$TiO_2$ film system was designed and developed in order to examine disinfection characteristics of sewage wastewater treatment. The optimum conditions for disinfection such as solar light intensity, characteristic of sewage wastewater, amounts of $TiO_2$ and comparison of solar ligth/$TiO_2$ systems with UV light/$TiO_2$ system was examined. The results are as follows: (1) photocatalytic disinfection process with solar light in the presence of $TiO_2$ film more effectively killed total coliform (TC) than solar light or $TiO_2$ film absorption only. (2) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with remain resistant material. (3) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with the increase of amounts of $TiO_2$. (4) TC survival ratio decreased linearly with increasing UV light intensity. (5) The disinfection effect of solar light/$TiO_2$ slurry system decreased more than UV light/$TiO_2$ film systems. (6) The disinfection reaction followed first-order kinetics. We suggest that solar light instead of using artificial UV light was conducted to investigate the applicability of alternative energy source in the disinfection of TC and the degradation of organic material.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.565-570
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• 2017

Tobacco smoke emitted during smoking is divided into a main-stream and side-stream smoke. Most of the tobacco smoke that spreads to a room while smoking is a side-stream one. The side-stream tobacco smoke is two to three times more harmful than that of the main-stream tobacco smoke. In this study, the removal efficiency of CO, $H_2S$, $NH_3$ and HCHO in a side-stream tobacco smoke using the doping component of $TiO_2$ photocatalysts was confirmed. As a result, CO was removed up to 78.37%, which indicated that the $TiO_2$ photocatalytic process is effective for CO removal. Also, the removal efficiencies of CO, $H_2S$ and HCHO were greatly affected by the amount of doped O and Si components of the $TiO_2$ photocatalyst. In conclusion, the more doped O and Si components had, the higher removal efficiencies of harmful substances were achieved.

• 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.