• Title, Summary, Keyword: photolysis

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A Novel Photoreaction of (2-Hydroxyethoxyphenyl)pentamethyldisilane

  • Park, Seung Ki;Seong, Won-Je
    • Bulletin of the Korean Chemical Society
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    • v.30 no.6
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    • pp.1331-1336
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    • 2009
  • Photolysis of (2-hydroxyethoxyphenyl)pentamethyldisilane 2 in benzene provides a novel intramolecular cyclization photoproduct 9 which was probably formed from the intramolecular reaction to form a seven-membered ring in silatriene intermediate 7 and then the photochemical disrotatory ring closure of 1,3-butadiene moiety to cyclobutene. Irradiation of 2 in methanol afforded photoproducts 5 and 6 which were formed by the nucleophilic attack of methanol to $\beta$ or $\alpha$ silicon atom in pentamethyldisilanyl group of the photoexcited state of 2. Compounds 10 and 11 were also formed by the same way as in the formation of the photoproducts 5 and 6 in the photolysis of (2-allyloxyethoxyphenyl)pentamethyldisilane 3 in methanol solvent. Photoreaction of (2-acetoxyethoxyphenyl) pentamethyldisilane 4 in methanol gave a photoproduct 12 which was formed via the elimination of dimethylsilylene species in the photoexcited state of 4.

Fabrication and Electro-photolysis Property of Carbon Nanotubes/Titanium Composite Photocatalysts for Methylene Blue

  • Zhang, Feng-Jun;Chen, Ming-Liang;Oh, Won-Chun
    • Bulletin of the Korean Chemical Society
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    • v.30 no.8
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    • pp.1798-1804
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    • 2009
  • In this study, we have studied on improved performance of carbon nanotubes/titanium (CNT/TiO2) structure electrode for methylene blue (MB). The composite electrodes consisting of CNTs and a titanium oxide matrix with phenol resin binder was fabricated with a mixture method. The chemical and morphological structure of CNT/Ti$O_2$ composites were characterized by means of BET surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis absorption technique, Raman spectroscopy and energy dispersive X-ray (EDX). The electrode showed a remarkably enhanced performance for MB oxidation under UV illumination with or without electro-chemical reaction (ECR). Such a remarkably improved performance of the CNT/Ti$O_2$ structure electrode might be due to the enhanced MB oxidation by electro- and photo-generated electrons and holes in the CNTs and Ti$O_2$ under UV illumination with or without ECR.

Removal of Sulfamethoxazole using Ozonation or UV Radiation; Kinetic Study and Effect of pH (오존 처리 및 UV 조사를 이용한 Sulfamethoxazole 제거; 동역학적 고찰 및 pH 영향)

  • Jung, Yeonjung;Kim, Wangi;Jang, Hayoung;Choi, Yanghwun;Oh, Byungsoo;Kang, Joonwun
    • Journal of Korean Society on Water Environment
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    • v.24 no.1
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    • pp.63-68
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    • 2008
  • This study was performed to assess the potential use of ozone or UV radiation for the treatment of water contaminated with sulfamethoxazole (SMX), which is frequently used antibiotic in human and veterinary medicines, especially focusing on the kinetic study and effect of pH. In a study using ozone alone, kinetic study was performed to determine second-order rate constant ($k_{O3,SMX}$) for the reactions of SMX with ozone, which was found to be $1.9{\times}10^6M^{-1}s^{-1}$ at pH 7. The removal efficiencies of SMX by ozone were decreased with increase of pH due to rapid decomposition of ozone under the condition of various pH (2.5, 5.3, 7, 8, 10). In a UV irradiation study at 254 nm, a kinetic model for direct photolysis of SMX was developed with determination of quantum yield ($0.08mol\;Einstein^{-1}$) and molar extinction coefficient ($15,872M^{-1}cm^{-1}$) values under the condition of quantum shielding due to the presence of reaction by-products formed during photolysis. For effect of pH on photolysis of SMX, SMX in the anionic state ($S^-$, pH > 5.6), most prevalent form at environmentally relevant pH values, degraded more slowly than in the neutral state (SH, 1.85 < pH < 5.6) by UV radiation at 254 nm.

Application of a Microbial Toxicity Assay for Monitoring Treatment Efficiency of Pentachlorophenol in Water using UV Photolysis and $TiO_2$ Photocatalysis

  • Kim, Jung-Kon;Cho, Il-Hyung;Zoh, Kyung-Duk;Choi, Kyung-Ho
    • Proceedings of the Korean Environmental Health Society Conference
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    • pp.146-150
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    • 2004
  • Degradation efficiency of pentachlorophenol (PCP) by using direct UV photolysis and $TiO_2$ photocatalysis was evaluated with both chemical analyses and acute toxicity assessment employing luminescent bacteria Vibrio fischeri. PCP was chosen as a target compound in this study because of its wide application as fungicide, bactericide, insecticide and wood preservative in agriculture and many industries, in addition to its well-known environmental consequences. The acute toxicity to the microbe was reduced by >60% when applying UV alone, and was completely removed when treated with $UV-TiO_2$ combinations. Toxicity reduction pattern determined with the Microtox Assay generally corresponds with the chemistry data: However, it should be noted that toxicity was greater than expected by the chemistry data. Formation of TCBQ, a toxic byprodut, could not explain observed microbial toxicity. These observations are probably due to the presence of unidentified toxic PCP byproducts, which may include polychlorinated dibenzodioxins and polychlorinated dibenzofurans. When Microtox results were compared between different exposure time, i.e.,5 min and 15 min, an interesting pattern was noted with $UVA-\;TiO_2$ treatment. While no microbial toxicity was observed with 5 min exposure, an EC50 value of 45.4% was estimated with 15 min exposure, which was not observed in $UVB-\;TiO_2$ exposure. This result may suggest the presence of unidentified toxic degradation products generated in the later stage of treatment. Based on this study, $TiO_2$ photocatalyst, together with UVB photolysis could improve the removal of both PCP and its toxic derivatives in more efficient way. The Microtox Assay is promising and economical method for monitoring efficiency of wastewater treatment processes.

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Characterization of Nickel Composite Plating with TiO2 Particles for Photolysis of Organic Compound (유기물 광분해용 니켈-TiO2 복합도금 전극 특성에 관한 연구)

  • Choi, Chul-Young;Cho, Seung-Chan;Ryu, Young-Bok;Kim, Young-Seok;Kim, Hyoung-Chan;Kim, Yang-Do
    • Journal of the Korean institute of surface engineering
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    • v.40 no.3
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    • pp.125-130
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    • 2007
  • Many fundamental studies have been carried out regarding waste water and hazardous gas treatment technology using the photolysis effect of $TiO_2$. However, photolysis of both organic and organic-inorganic binders immobilizing $TiO_2$ makes permanent use impossible. In this study we manufactured a catalytic electrode by nickel-$TiO_2$ composite plating in order to immobilize $TiO_2$. The surface properties according to the current density changes of cathode and concentration changes of $TiO_2$ powder in nickel plating bath has been analysed with EDX, XRF, SEM, Raman spectrometer etc. The characterization of the catalytic electrode in decomposition of organic compound has been obtained by using UV-Visible spectrophotometer through analysing concentration changes of methyl orange solution containing the catalytic electrode vs. time with projecting UV-light in the solution. The study shows that a catalytic electrode of nickel-$TiO_2$ composite plating with high-efficiency in decompostion of organic compound has been formed under high concentration of $TiO_2$ powder and low current density of cathode.

Behaviors of the Fungicide Procymidone in Soils (살균제 Procymidone의 토양 중 동태)

  • Choi, Gyu-Il;Seong, Ki-Yong;Kim, Jeong-Gyu
    • Korean Journal of Environmental Agriculture
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    • v.24 no.2
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    • pp.123-131
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    • 2005
  • This study was focused on adsorption, leaching, photolysis, and hydrolysis of the fungicide procymidone in soils. Adsorption type of procymidone on three different soil were well fitted to Linear and Freundlich isotherm. Distribution coefficients (Kd) were ranged from 2.75 to 12.18 and Freundlich isotherm Kf value $1.99{\sim}9.98$, 1/n value $0.74{\sim}0.89$. Desorption rates were $20.1{\sim}34.0%$ (Namgye), $26.3{\sim}44.6%$ (Jigog) and $31.6{\sim}50.9%$ (Baegsan series) and desorption hysteresis were $0.65{\sim}0.79,\;0.55{\sim}0.73\;and\;0.49{\sim}0.68$. Procymidone seemed to be stable to photolysis in acidic and neutral solutions but hydrolyzed rapidly in alkaline solution. Considering leaching properties procymidone mobility low in soils.

A Study on the Degradation of Parathion and Reduction of Acute Toxicity in Solar $TiO_2$ Photocatalysis (태양광 $TiO_2$ 광촉매를 이용한 Parathion의 분해와 독성저감에 관한 연구)

  • Kim, Tak-Soo;Kim, Jung-Kon;Choi, Kyung-Ho;Zoh, Kyung-Duk
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.8
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    • pp.822-828
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    • 2005
  • The photocatalytic degradation of methyl parathion was carried out using a circulating $TiO_2$/solar system. Under the photocatalytic condition, parathion was more effectively degraded than by the photolysis or $TiO_2$ only condition. The parathion degradation followed pseudo first-order kinetics. With photocatalysis, 10 mg/L parathion was completely degraded within 90 min with a TOC decrease exceeding 63% after 150 min. The nitrogen from parathion was recovered mainly as ${NO_2}^-$, ${NO_3}^-$, and ${NH_4}^+$, 80% of sulfur as ${SO_4}^{2-}$, and less than 5% of phosphorus as ${PO_4}^{3-}$ during photocatalysis. The organic intermediates 4-nitrophenol and paraoxon were also identified, and these were further degraded. Two different bioassays using V. fischeri and D. magna were employed to measure the toxicity reduction in the solutions treated by both photocatalysis and photolysis. Relative toxicity was reduced almost completely after 150 min in both organisms under the photocatalysis, whereas in photolysis, 76 and 57% reduction was achieved for V. fischeri and D. magna, respectively. The acute toxicity reduction pattern corresponded with the decrease in parathion and TOC concentrations.

High-Yield Gas-Phase Laser Photolysis Synthesis of Germanium Nanocrystals for High-Performance Lithium Ion Batteries (고성능 리튬이온 전지를 위한 저마늄 나노입자의 가스상 레이저 광분해 대량 합성법 개발)

  • Kim, Cang-Hyun;Im, Hyung-Soon;Cho, Yong-Jae;Chung, Chan-Su;Jang, Dong-Myung;Myung, Yoon;Kim, Han-Sung;Back, Seung-Hyuk;Im, Young-Rok;Park, Jeung-Hee;Song, Min-Seob;Cho, Won-Il;Cha, Eun-Hee
    • Journal of the Korean Electrochemical Society
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    • v.15 no.3
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    • pp.181-189
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    • 2012
  • We developed a new high-yield synthesis method of free-standing germanium nanocrystals (Ge NCs) by means of the gas-phase photolysis of tetramethyl germanium in a closed reactor using an Nd-YAG pulsed laser. Size control (5-100 nm) can be simply achieved using a quenching gas. The $Ge_{1-x}Si_x$ NCs were synthesized by the photolysis of a tetramethyl silicon gas mixture and their composition was controlled by the partial pressure of precursors. The as-grown NCs are sheathed with thin (1-2 nm) carbon layers, and well dispersed to form a stable colloidal solution. Both Ge NC and Ge-RGO hybrids exhibit excellent cycling performance and high capacity of the lithium ion battery (800 and 1100 mAh/g after 50 cycles, respectively) as promising anode materials for the development of high-performance lithium batteries. This novel synthesis method of Ge NCs is expected to contribute to expand their applications in high-performance energy conversion systems.

Effect of Effluent Organic Matters on Estrogenic Activity Reduction of Bisphenol A by Photolysis (광분해 반응에 의한 비스페놀 A의 에스트로겐 활성 저감에 미치는 방류수 유기물질의 영향)

  • Yoo, Jisu;Na, Joolim;Jung, Jinho
    • Korean Journal of Environmental Biology
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    • v.34 no.1
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    • pp.48-55
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    • 2016
  • This study investigates the effect of effluent organic matter (EfOM) from sewage wastewater treatment plants on estrogenic activity reduction of bisphenol A (BPA) by UV photolysis. The EfOM and Suwannee River natural organic matter (SR-NOM) as reference were isolated into hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) fractions depending on polarity. The specific ultraviolet absorbance (SUVA) analysis indicated that EfOM showed similar properties to microbially derived organic matters with low hydrophobicity, which is different from SR-NOM having high hydrophobicity. UV irradiation upto 3 hr significantly reduced SUVA values of both EfOM and SR-NOM (p<0.0001), depending on the polarity of organic matters. In the absence of organic matters, the relative estrogenic activity (REA) of BPA ($5.0{\times}10^{-5}M$) was decreased from 86% to 63% by UV photolysis (2 hr). However, the decrease of mean REA was from 68% to 37% in the presence of organic matters, which was significantly independent on the type (EfOM or SR-NOM) and polarity (HPO, TPI or HPI) of organic matters (p>0.05). As a result, the reduced REA by UV photolysis of BPA with and without organic matters was 31% and 23%, respectively, suggesting that both EfOM and SR-NOM accelerated the photolytic reduction of BPA estrogenic activity.