• Title, Summary, Keyword: Photodegradation

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Photocatalytic Degradation of Trichloroethylene in Aqueous Phase (수중 Trichloroethylenel의 광촉매 분해특성에 관한 연구)

  • Jo, Sung-Hye;Nam, Ju-Hee;Kim, Il-Kyu
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.4
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    • pp.555-564
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    • 2011
  • The photocatalytic degradation of trichloroethylene (TCE) 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 $TiO_2$ get at $500^{\circ}C$ for 1hr. The Langmuir-Hinshelwood model is applicable to describe the photodegradation, which indicates that adsorptionof the solute on the surface of $TiO_2$ particles plays an important role in photodegradation. Photocatalysts with various transition metals (Nd, Pd and Pt) loading are tested to evaluate the effect of transition metal impurities on photodegradation. The photodegradation efficiencies with $TiO_2$ including Pt, Pd and Nd are lower than pure $TiO_2$ powder. The effect of pH is investigated and the maximum photodegradation efficiency is obtained at pH 7. In addition, the intermediates such as dichloromethane, chloroform, and trichloroethane are detected during the photodegradation of TCE.

Characteristics of Photochemical Reaction of Pefloxacin Irradiated by UVB in an Aerobic Condition (산소 존재하에서 UVB에 의한 페플록사신의 광화학적 반응의 특성)

  • 최윤수;이경선
    • YAKHAK HOEJI
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    • v.44 no.1
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    • pp.36-40
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    • 2000
  • The photodegradation of pefloxacin, photolabile fluoroquinolone antibacterial agent, was studied. In the presence of $N_2$, photodegradation of pefloxacin was suppressed. The singlet oxygen and free radical generated in the reaction media proceeded photochemical reaction. The photodegradation of peflxacin was sensitized by benzophenone, a triplet state sensitizer.

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Photodegradation of Pyrene, Chrysene and Benzo[a]pyrene in Water (I) (수중의 Pyrene, Chrysene 및 Benzo[a]pyrene의 광분해(I))

  • 김지용;허철구;이민규;감상규
    • Journal of Environmental Science International
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    • v.12 no.3
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    • pp.337-344
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    • 2003
  • The photodegradation of pyrene, chrysene and benzo[a]pyrene, that were similar in structure among poly-cyclic aromatic hydrocarbons (PAMs), were investigated in water irradiated with a low-pressure mercury lamp (wavelength of 253.7 nm and UV output of 1.35 ${\times}$ 10$\^$-3/J/s). The effects of several factors (t-BuOH, HCO$_3$$\^$-/ and pH) on photodegradation of above three PAHs were also examined. The photodegradation rates of PAHs decreased with increasing the concentration of t-BuOH, but decreased little with increasing the concentration of HCO$_3$$\^$-/ under the concentrations used in this study. The photodegradation rates of PAHs decreased with increasing pH, but their change were greater in case of pH increase from acid to neutral and were little in case of pH increase from neutral to base. The photodegradation rates of PAMs fitted a first-order kinetic model and their photodegradation rates decreased in the following sequences: pyrene>chrysene>benzo[a]pyrene among the PAHs used.

Sensitized Photodegradation of Benzene in Water

  • Kim, Young-Hee;Ahn, Sang-Jun;Park, Hyun-Geoun;Lee, Chun-Sik
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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    • v.4 no.2
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    • pp.79-84
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    • 2000
  • The photodegradation of benzene was studied in an aqueous solution using a medium pressure Hg-lamp. In this study, persulfate, nitrate, nitrite, chloride, and sulfate ions were all tested as sensitizers. The persulfate, nitrate, and nitrite ions exhibited a sensitizing effect in the photodegradation of benzene, whereas no detectable effects were observed with the sulfate and chloride ions. When nitrite ions were used as the sensitizer, the photodegradation of benzene ran through a maximum value and thereafter decreased with an increasing nitrite concentration. The resulting build-up of nitrite ions seemed to scavenge the hydroxyl radicals. When nitrite ions were present along with persulfate ions, the photodegradation of benzene was inhibited.

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Photocatalytic Degradation of Gaseous Acetaldehyde through TiO2-Coated Fly Ash Composites (TiO2 코팅 석탄회 복합체의 기상 Acetaldehyde 광분해 특성)

  • Shin, Dae-Yong;Kim, Kyung-Nam
    • Journal of the Korean Ceramic Society
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    • v.45 no.1
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    • pp.43-47
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    • 2008
  • The photocatalyst of $TiO_2$ coated on a fly ash composites (TCF) was prepared from precipitant dropping method to remove the acetaldehyde by photocatalytic reaction. The TCF were characterized by crystal aize, crystal structure and specific surface area. The photodegradation of acetaldehyde has been investigated using a UV-illuminated fixed photocatalytic reactor with TCF catalyst and P-25 catalyst in gas phase. The effect of photodegradation reaction conditions, such as initial concentration of acetaldehyde, concentration of oxidant in mixed gas and the light intensity on the photodegradation of acetaldehyde were investigated. P-25 catalyst showed the highest photodegradation of acetaldehyde and anatase $TiO_2$ coated TCF showed higher decomposition rate than rutile coated TCF. The photodegradation rate of acetaldehyde increased with the decrease of flow rate, initial concentration of acetaldehyde ($C_i$) and water vapor, however, it was increased with the increas of UV light intensity. The optimum conditions were weight of TCF=10 g, flow rate=50 ml/min $C_i$=100 ppm, concentration of oxygen=20%, concentration of water vapor=100 ppm.

Degradation and mineralization of violet-3B dye using C-N-codoped TiO2 photocatalyst

  • Putri, Reza Audina;Safni, Safni;Jamarun, Novesar;Septiani, Upita;Kim, Moon-Kyung;Zoh, Kyung-Duk
    • Environmental Engineering Research
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    • v.25 no.4
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    • pp.529-535
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    • 2020
  • The present study investigated the photodegradation of synthetic organic dye; violet-3B, without and with the addition of C-N-codoped TiO2 catalyst using a visible halogen-lamp as a light source. The catalyst was synthesized by using a peroxo sol-gel method with free-organic solvent. The effects of initial dye concentration, catalyst dosage, and pH solution on the photodegradation of violet-3B were examined. The efficiency of the photodegradation process for violet-3B dye was higher at neutral to less acidic pH. The kinetics reaction rate of photodegradation of violet-3B dye with the addition of C-N-codoped TiO2 followed pseudo-first order kinetics represented by the Langmuir-Hinshelwood model, and increasing the initial concentration of dyes decreased rate constants of photodegradation. Photodegradation of 5 mg L-1 violet-3B dye achieved 96% color removal within 240 min of irradiation in the presence of C-N-codoped TiO2 catalyst, and approximately 44% TOC was removed as a result of the mineralization.

Photodegradation of Pyrene, Chrysene and Benzo[a]pyrene in Water (II) (수중의 Pyrene, Chrysene 및 Benzo[a]pyrene의 광분해(II))

  • 감상규;김지용;주창식;이민규
    • Journal of Environmental Science International
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    • v.12 no.7
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    • pp.775-782
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    • 2003
  • The photodegradations of pyrene, chrysene and benzo[a]pyrene that were similar in structure among polycyclic aromatic hydrocarbons (PAHs) were investigated with a low-pressure mercury lamp(the wavelength of 253.7 nm and UV output of 1.35${\times}$10$\^$-3/J/s). The optimum concentrations of TiO$_2$ and H$_2$O$_2$ on the photodegradation of pyrene, chrysene and benzo[a]pyrene were 1 g/L and 1.5${\times}$10$\^$-3/ M, respectively. By these optimum concentrations, their rates increased with increasing the concentration of TiO$_2$ and H$_2$O$_2$ because the amounts of OH radical formed increased, but for the higher concentrations than the optimum, their rates decreased with increasing those concentrations because the white turbidity phenomena occurs in case of TiO$_2$ and H$_2$O$_2$ acts as an OH radical inhibitor. The photodegradation rates among the photodegradation processes such as UV, UV/TiO$_2$, UV/H$_2$O$_2$, and UV/H$_2$O$_2$/TiO$_2$ decreased in the following sequences.: UV/H$_2$O$_2$/TiO$_2$> UV/H$_2$O$_2$> UV/TiO$_2$> UV.

Photodegradation of Endosulfan alpha, beta, and sulfate in Aqueous Solution by UV Irradiation Only (자외선 조사에 의한 수용액 중에 함유되어 있는 엔도설판 alpha, beta, sulfate의 광분해)

  • Ryoo, Keon-Sang;Kim, Mi-Hyang;Lee, Hwa-Sung;Hwang, Hyun-Gick
    • Journal of Environmental Science International
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    • v.15 no.11
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    • pp.1061-1067
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    • 2006
  • Photodegradation of endosulfan alpha, beta, and sulfate known as the most toxic substance among organochlorine pesticides by UV irradiation was studied at experimental conditions such as different pH aqueous solution and reaction time. The initial concentration of endosulfan alpha, beta, and sulfate in aqueous solution was 500 ppb, respectively. The experiment of photodegradation was conducted in a quartz reactor equipped with a low pressure mercury lamp (100 W, 240 nm). The samples were withdrawn from the photo reactor at intervals of 0, 10 min, 30 min, 1 hr, 2 hr, and 4 hr. Endosulfan sulfate was never hydrolyzed and photodegraded in wide range of pH. At pH 5 and reaction time (240 min), endosulfan alpha was photodegraded up to 67%. Both endosulfan alpha and beta were started to photodegrade at pH 6.5 with the lapse of time, resulting in approximately 99.9% and 87.2% of photodegradation efficiency, respectively. Furthermore, at pH 9, endosulfan alpha and beta was partially hydrolyzed and photodegraded to 99.5% at 120 min of reaction time. During the photolysis, any photo-products of endosulfan alpha, beta, and sulfate were not observed.

Photocatalytic Degradation of Dibenzothiophene in Aqueous Phase (수중 Dibenzothiophene의 광촉매 분해에 관한 연구)

  • Jo, Sung-Hye;Yoe, Seok-Jun;Kim, Il-Kyu
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.4
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    • pp.527-534
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    • 2011
  • In this research, the photocatalytic degradation of dibenzothiophene (DBT) 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 photodegradation efficiencies with $TiO_2$ including Pt and Pd are higher than pure $TiO_2$ powder. Also we investigated the applicability of $H_2O_2$ to increase the efficiency of the $TiO_2$ photocatalytic degradation of dibenzothiophene. The degradation efficiency increases with increasing dosage of $H_2O_2$ in the range of 0.01M to 0.1M . The effect of pH is investigated; we obtained the maximum photodegradation efficiency at pH 5. In addition, the intermediate analysis found dihydroxyl -dibenzothiophene as a reaction intermediate of dibenzothiophene during the photodegradation.

Study of Degradation of Organic matter using prepared Titania by Metal ions substitution process (금속이온 치환법으로 제조된 티타니아를 이용한 유기물 분해에 대한 연구)

  • Lee, Gyu-Hwan;Rhee, Dong Seok
    • Journal of Industrial Technology
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    • v.28 no.A
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    • pp.19-22
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    • 2008
  • In recent years, much attention has been paid to "Photocatalytic oxidation" as an alternative technique, where the pollutants are degraded by UV-irradiation in the presence of a semiconductor suspension such as titanium dioxide. $TiO_2$ is the most often used photocatalyst due to its considerable photocatalytic activity, high stability, non-environmental impact and low cost. 1n this research, the photocatalytic degradation of humic acid, acetaldehyde and methylene blue in $UV/TiO_2$ systems has been stydied. The effect of calcination temperature for manufacturing of $TiO_2$ photocatalysts and type of photocatalysts on photodegradation has been investigated. Photocatalysts with various metal ions(Mn, Fe, Cu and Pt) loading are tested to evaluate the effects of metal ions impurities on photodegradation. The photodegradation efficiency with $Pt-TiO_2$ or $Fe-TiO_2$ or $Cu-TiO_2$ is higher than Degussa P-25 powder. However, the photodegradation efficiency with $Mn-TiO_2$ is lower than Degussa P-25 powder. The photocatalytic properties of the nanocrystals were strongly dependent upon the crystallinity, particle size, standard reduction potential of various transition metal and electronegativity of various transition metal. As a result photocatalysts with various metal ion loading evaluated the effect of photodegradation.

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