• Title, Summary, Keyword: Photocatalytic oxidation

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Photocatalytic oxidation reaction in removal of NH4-N by using TiO2 (TiO2를 이용한 암모니아성 질소 제거에 관한 광촉매 산화반응)

  • 박상원;김정배
    • Journal of Environmental Science International
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    • v.12 no.10
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    • pp.1071-1077
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    • 2003
  • The aim of this study is, firstly, to find out what kinds of inorganic species are produced in the photocatalytic oxidation of ammonium-nitrogen containing water and, secondly, to seek the influence of anion for the photocatalytic oxidation of ammonium contained compounds. The photoenergy above 3 eV(λ <415 nm) was effectively absorbed by TiO$_2$ and TiO$_2$/polymer was used to be oxidized NH$_4$-N in wastewater to NO$_3$-N. Existing the anion as Cl$\^$-/, the rate of photocatalytic oxidation decreased regardless of other condition. This result showed that the chloride ions reduced the rate of oxidation by scavenging oxidizing radical species as OH$\^$-/ and OCl$\^$-/. Some of the added ion might have blocked the active sites of the catalyst surface, thus deactivated the catalyst.

Treatment of Odorous air pollutants by Plasma and Photocatalytic Process. (플라즈마 광촉매 복합 긍정을 이용한 악취물질 중 TEA, MEK의 분해처리)

  • 최금찬;정창훈
    • Journal of Environmental Science International
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    • v.12 no.12
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    • pp.1255-1260
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    • 2003
  • Plasma-photocatalytic oxidation process was applied in the decomposition of Triethylamine(TEA) and Methyl ethyl ketone(MEK). Plasma reactor was made entirely of pyrex glass and consists of 24mm inner diameter, 1,800mm length and discharge electrode of 0.4mm stainless steel. And initial concentrations of TEA and MEK for plasma-photocatalytic oxidation are 100 ppm. Odor gas samples were taken by gas-tight syringe from a glass sampling bulb which was located at reactor inlet and outlet, and TEA and MEK were determined by GC-FID. For plasma process, the decomposition efficiency of TEA and MEK were evaluated by varying different flowrates and decomposition efficiency of TEA and MEK increased considerably with decreasing treatment flowrates. For photocatalytic oxidation process, also the decomposition efficiency of TEA and MEK increased considerably with decreasing treatment flowrates. The decomposition efficiency of MEK was 57.8%, 34.2%, 18.8% respectively and the decomposition efficiency of TEA was reached all 100%. This result is higher than that of plasma process only, From this study, the results indicate that plasma-photocatalytic oxidation process is ideal for treatment of TEA and MEK.

Gas phase Photocatalytic Oxidation of PCE with $TiO_2$ ($TiO_2$를 이용한 PCE의 기상 광산화처리)

  • 조인철;변종환;변은숙;이동근;김성우
    • Journal of Korean Society for Atmospheric Environment
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    • v.17 no.1
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    • pp.57-66
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    • 2001
  • Gas phase photocatalytic oxidation of tetrachloroethylene (PCE) under 370 nm ultra-violet irradiation was investigated with TiO$_2$ catalyst. During the photocatalytic oxidation of PCE vapor several kinds of intermediate were produced, and the reaction pathways were proposed on the basis of the production sequency of the intermediates. The intermediates in the pathways of PCE oxidation were hexachloroethane, pentachlotoethane, 1, 1, 2-trichloroethane, carbon tetrachl-oride, dichloroacetylchloride, chloroform, 1,1-dichloroethane, phosgene, CO, $CO_2$, HCl, Cl$_2$.

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Durability of Photocatalytic Cement after Nitric Oxide-Wet-Dry Cycling

  • Lee, Bo Yeon;Kurtis, Kimberly E.
    • Journal of the Korea Institute of Building Construction
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    • v.14 no.4
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    • pp.359-368
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    • 2014
  • Photocatalytic cement has been receiving attention due to its high oxidation power that reduces nitrogen oxide, thus contributing to a clean atmospheric environment. However, there has not yet been a thorough investigation on the effect of photocatalytic reactions on the durability of cementitious material, the parent material. In this study, photocatalytic cement samples were exposed to nitric oxide gas and UV along with cycles of wetting and drying to simulate environmental conditions. The surface of samples was characterized mechanically, chemically, and visually during the cycling. The results indicate that that the photocatalytic efficiency decreased with continued NO oxidation. The pits found from SEM indicated that chemical deterioration, such as acid attack or leaching, did occur. However, this was not confirmed by X-ray diffraction. The hardness was not affected, probably due to the formation of CSH as evidenced by the XRD pattern. In conclusion, it was found that photocatalysis could alter cementitious materials both chemically and mechanically, which could further affect long-term durability.

A Study on the Removal of Chloro-Phenols by Photocatalytic Oxidation (광촉매(光觸媒) 산화(酸化) 반응(反應)을 이용한 클로로페놀 분해(分解)에 관한 연구(硏究))

  • Lee, Sang Hyup;Park, Ju Seok;Park, Chung Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.9 no.4
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    • pp.87-96
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    • 1995
  • The Electron/Hole Pair is generated when the activation energy produced by ultraviolet ray illuminates to the semiconductor and OH- ion produced by water photocleavage reacts with positive Hole. As a results, OH radical acting as strong oxidant is generated and then Photocatalytic oxidation reaction occurs. The photocatalytic oxidation can oxidate the non-degradable and hazardous organic substances such as pesticides and aromatic materials easier, safer and shorter than conventional water treatment process. So in this study, many factors influencing the oxidation of chlorophenols, such as inorganic electrolytes addition, change of oxygen and nitrogen atmosphere, temperature, pH, oxygen concentration, chlorophenol concentration, were throughly examined. According to the experiments observations, it is founded that the rate of chlorophenol oxidation follows a first-order reaction and the modified Langmuir-Hinshelwood relationship. And the photocatalytic oxidation occurs only when activation energy acting as Electron/Hole generation, oxygen acting as electron acceptor to prevent Electron/Hole recombination, $TiO_2$ powder acting as photocatalyst are present. The effects of variation of dissolved oxygen concentration, temperature and inorganic electrolytes concentration on 2-chlorophenol oxidation are negligible. And the lower the organic concentration, the higher the oxidation efficiency becomes. Therefore, the photocatalytic oxidation is much effective to oxidation of hazardous substances at very low concentration. The oxidation is effective in the range of 0.1 g/L-10 g/L of $TiO_2$. Finally when the ultra-violet ray is illuminated to $TiO_2$, the surface characteristics of $TiO_2$ change and Adsorption/Desorption reaction on $TiO_2$ surface occurs.

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Gaseous by-products from the TiO2 Photocatalytic Oxidation of Benzene

  • Han, Sang-Wook;Lee, Jin-Hong;Kim, Jin-Seog;Oh, Sang-Hyub;Park, Young-Kwon;Kim, Hyun-Ook
    • 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.

Development for UV/TiO2 Photocatalytic Oxidation Indoor Air Compound Process (광촉매/광산화를 이용한 VOCs 처리장치 개발)

  • Jeon, Bo-Kyung;Choi, Kum-Chan;Suh, Jeong-Min
    • Journal of Environmental Science International
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    • v.15 no.9
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    • pp.855-864
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    • 2006
  • This study introduces a method to eliminate formaldehyde and benzene, toluene from indoor air by means of a photocatalytic oxidation reaction. In the method introduced, for the good performance of the reaction, the effect and interactions of the $TiO_2$ catalyst and ultraviolet in photocatalytic degradation on the reaction area, dosages of catalysts, humidity and light should be precisely examined and controled. Experiments has been carried out under various intensities of UV light and initial concentrations of formaldehyde, benzene and toluene to investigate the removal efficiency of the pollutants. Reactors in the experiments consist of an annular type Pyrex glass flow reactor and an 11W germicidal lamp. Results of the experiments showed reduction of formaldehyde, benzene and toluene in ultraviolet $/TiO_2/$ activated carbon processes (photooxidation-photocatalytic oxidation-adsorption processes), from 98% to 90%, from 98% to 93% and from 99% to 97% respectively. Form the results we can get a conclusion that a ultraviolet/Tio2/activated carbon system used in the method introduced is a powerful one for th treatment of formaldehyde, benzene and toluene of indoor spaces.

Removal of Bisphenol-A using Rotating Photocatalytic Oxidation Drum Reactor (RPODR)

  • Son, Hee-Jong;Jung, Chul-Woo;Kim, Seung-Hyun
    • Environmental Engineering Research
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    • v.13 no.4
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    • pp.197-202
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    • 2008
  • This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

Doping a metal (Ag, Al, Mn, Ni and Zn) on TiO2 nanotubes and its effect on Rhodamine B photocatalytic oxidation

  • Gao, Xinghua;Zhou, Beihai;Yuan, Rongfang
    • 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%.

Evaluation of Oxidation Efficiency of Aromatic Volatile Hydrocarbons using Visible-light-activated One-Dimensional Metal Oxide Doping Semiconductor Nanomaterials prepared by Ultrasonic-assisted Hydrothermal Synthesis (초음파-수열합성 적용 가시광 활성 일차원 금속산화물 도핑 반도체 나노소재를 이용한 방향족 휘발성 탄화수소 제어효율 평가)

  • Jo, Wan-Kuen;Shin, Seung-Ho;Choi, Jeong-Hak;Lee, Joon Yeob
    • Journal of Environmental Science International
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    • v.27 no.11
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    • pp.967-974
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    • 2018
  • In this study, we evaluated the photocatalytic oxidation efficiency of aromatic volatile hydrocarbons by using $WO_3$-doped $TiO_2$ nanotubes (WTNTs) under visible-light irradiation. One-dimensional WTNTs were synthesized by ultrasonic-assisted hydrothermal method and impregnation. XRD analysis revealed successful incorporation of $WO_3$ into $TiO_2$ nanotube (TNT) structures. UV-Vis spectra exhibited that the synthesized WTNT samples can be activated under visible light irradiation. FE-SEM and TEM images showed the one-dimensional structure of the prepared TNTs and WTNTs. The photocatalytic oxidation efficiencies of toluene, ethylbenzene, and o-xylene were higher using WTNT samples than undoped TNT. These results were explained based on the charge separation ability, adsorption capability, and light absorption of the sample photocatalysts. Among the different light sources, light-emitting-diodes (LEDs) are more highly energy-efficient than 8-W daylight used for the photocatalytic oxidation of toluene, ethylbenzene, and o-xylene, though the photocatalytic oxidation efficiency is higher for 8-W daylight.