• Journal of Power System Engineering
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• v.18 no.6
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• pp.133-139
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• 2014

In this research, the photocatalytic degradation of benzothiophene in $TiO_2$ aqueous suspension has been studied. $TiO_2$ photocatalysts are prepared by a sol-gel method. The dominant anatase-structure on $TiO_2$ particles is observed after calcining the $TiO_2$ gel at $500^{\circ}C$ for 1hr. Photocatalysts with various transition metals (Nd, Pd and Pt) loading are tested to evaluate the effect of transition metal impurities on photodegradation. The photocatalytic degradation in most cases follows first-order kinetics. The maximum photodegradation efficiency is obtained with $TiO_2$ dosage of 0.4g/L. The photodegradation efficiency with Pt-$TiO_2$ is higher than pure $TiO_2$ powder. The optimal content value of Pt is 0.5wt.%. Also we investigate the applicability of $H_2O_2$ to increase the efficiency of the $TiO_2$ photocatalytic degradation of benzothiophene. The optimal concentration of $H_2O_2$ is 0.05. The effect of pH is investigated; we obtain the maximum photodegradation efficiency at pH 9. Hydroxy-benzothiophenes and dihydroxy-benzothiophenes are identified as reaction intermediates. It is proposed that benzothiophene is oxidized by OH radical to sequentially form hydroxyl-benzothiophenes, dihydroxybenzothiophenes, and benzothiophenedione.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E2
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• pp.35-42
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• 2001

Recent development of photocatalytic degradation method that is mediated by TiO$_2$ is of interest in the treatment of volatile organic compounds(VOCs). In this study, trichloroethylene(TCE) and acetone were closely examined in a batch scale of photo-reactor as a function of water vapor, oxygen, and temperature. Water vapor inhibited the photocatalytic degradation of acetone, while there was an optimum concentration in TCE. A lower efficiency was found in nitrogen atmosphere than air, and the effect of oxygen on photocatalytic degradation of acetone was greater than on that of TCE. The optimum reaction temperature on photocatalytic degradation was about 45$^{\circ}C$ for both compounds. NO organic byproducts were detected for both compounds under the present experimental conditions. It was ascertained that the photocatalytic reaction in a batch scale of photo-reactor was very effective in removing VOCs such as TCE and acetone in the gaseous phase.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.185-197
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• 2019

Deactivation of porous photocatalytic materials was studied using three types of microstructured particles: macroporous titania particles, titania microspheres, and porous silica microspheres containing CNTs and $TiO_2$ nanoparticles. All particles were synthesized by emulsion-assisted self-assembly using micron-sized droplets as micro-reactors. During repeated cycles of the photocatalytic decomposition reaction, the non-dimensionalized initial rate constants (a) were estimated as a function of UV irradiation time (t) from experimental kinetics data, and the results were plotted for a regression according to the exponentially decaying equation, $a=a_0\;{\exp}(-k_dt)$. The retardation constant ($k_d$) was then compared for macroporous titania microparticles with different pore diameters to examine the effect of pore size on photocatalytic deactivation. Nonporous or larger macropores resulted in smaller values of the deactivation constant, indicating that the adsorption of organic materials during the photocatalytic decomposition reaction hinders the generation of active radicals from the titania surface. A similar approach was adopted to evaluate the activation constant of porous silica particles containing CNT and $TiO_2$ nanoparticles to compare the deactivation during recycling of the photocatalyst. As the amount of CNTs increased, the deactivation constant decreased, indicating that the conductive CNTs enhanced the generation of active radicals in the aqueous medium during photocatalytic oxidation.

• Environmental Engineering Research
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• v.13 no.1
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• pp.14-18
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• 2008

Photocatalytic oxidations of benzene gas using the closed system (batch reactor) were induced to determine its by-products and investigate the effect of humidity and oxygen concentration on their generation. The study was able to identify 11 gaseous by-products: 2-methylpropene, acetaldehyde, acetone, pentane, methylcyclobutane, methylcyclopentane, cyclohexane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, and hexane. All the by-products were saturated hydrocarbons, which are less toxic than benzene and were probably formed through hydrogenation reaction on the photocatalytic surface. The photocatalytic oxidation of benzene under higher humidity produced less by-products. However, the amount of acetone released increased with higher humidity and oxygen concentration.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E3
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• pp.117-124
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• 2001

The present paper examined the kinetics of photocatalytic degradation of volatile organic compounds (VOCs) including gaseous trichloroethylene (TCE) and acetone. In this study, we examined the effects of the initial concentration of VOCs and the light intensity of ultra-violet (UV). A batch photo-reactor was specifically designed for this work. The photocatalytic degradation rate increased with the initial concentration of VOCs but remained almost constant beyond a certain concentration. It matched well with the Langmuir-Hinshelwood (L-H) kinetic model. When the effect of light intensity was concerned, it was found that photocatalytic degradation occurs in two regimes with respect to light intensity.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.282-287
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• 2011

ACF and $WO_3$ modified $TiO_2$ composites (ACF/$WO_3$/$TiO_2$) were prepared using a sol-gel method. The composites were characterized by Brunauer.Emmett.Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and scanning electron microscope (SEM) analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of the MO was determined using UV/Vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase of the photo-absorption effect by the $WO_3$ and the cooperative effect of the ACF.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.571-576
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• 2011

Activity carbon (AC), Cu and $Cu_2O$ modified $TiO_2$ composites (Cu/$Cu_2O$-AC/$TiO_2$) were prepared using a sol-gel method. The characteristics of the composites were evaluated using Brunauer-Emmett-Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and scanning electron microscope (SEM) analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of MO was determined using UV/Vis spectrophotometry. $Cu_2O$, Cu and the cooperative effect of the AC increased the photo-absorption effect, thus increasing in photocatalytic activity.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.433-438
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• 2011

In this study, CdS combined activated carbon/$TiO_2$ (CdS-AC/$TiO_2$) composites were prepared by a sol-gel method to improve the photocatalytic performance of $TiO_2$. These composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and UV-vis analysis. The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible light irradiation. The photodegradation rate of MB under visible light irradiation reached 90.1% in 120 min. The kinetics of MB degradation was plotted alongside the values calculated from the Langmuir-Hinshelwood equation. The 0.2 CAT sample showed the best photocatalytic activity, which might be due to an increase in the photo-absorption effect by activated carbon and the cooperative effect of CdS.

• 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.

• Environmental Engineering Research
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• v.20 no.4
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• pp.329-335
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• 2015

The effects of ion-doping on $TiO_2$ nanotubes were investigated to obtain the optimal catalyst for the effective decomposition of Rhodamine B (RB) through UV photocatalytic oxidation process. Changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the BET surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on RB removal increased when $Ag^+$, $Al^{3+}$ and $Zn^{2+}$ were doped into the $TiO_2$ nanotubes, whereas such activities decreased as a result of $Mn^{2+}$ or $Ni^{2+}$ doping. In the presence of $Zn^{2+}$-doped $TiO_2$ nanotubes calcined at $550^{\circ}C$, the removal efficiency of RB within 50 min was 98.7%.