• Title/Summary/Keyword: Oxidation kinetics

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Treatment of Cu-EDTA by using Photocatalytic Oxidation Process - Comparison between UV Lamp and Solar Light - (광산화 공정을 이용한 Cu-EDTA 처리 - 인공 자외선램프와 태양광의 처리경향 비교 -)

  • Shin, In-Soo;Choi, Bong-Jong;Lee, Seung-Mok;Yang, Jae-Kyu
    • Journal of Korean Society on Water Environment
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    • v.21 no.1
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    • pp.66-72
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    • 2005
  • Effect of the pH, molar ratio of Cu(II)/EDTA, concentration of Cu(II)-EDTA and ionic strength on the photocatalytic oxidation(PCO) of Cu(II)-EDTA in solar light was studied in this work. Experimental results in this work were compared with previous results obtained with UV-lamp. In the kinetics, Cu(II)-EDTA decomposition was favorable below neutral pH. The removal of Cu(II) and DOC was favorable as $TiO_2$ dosage increased. The initial rate for the decomplexation of Cu(II)-EDTA linearly increased as the concentration of Cu(II)-EDTA increased. The removal of Cu(II) and DOC was not much affected by variation of ionic strength with $NaClO_4$ as a background ion while much reduction was observed in the presence of background ions having higher formal charges. The removal trend of Cu(II) and DOC with variation of ionic strength and concentration of Cu(II)-EDTA in solar light was similar with that in UV light. Variation of the molar ratio of Cu(II)/EDTA showed a negligible effect on the removal of both Cu(II) and DOC. However, removal of both Cu(II) and DOC was two-times greater than that previous results obtained with UV light.

Phase Transitions In Nonstoichiometric Titanium Oxide Thin Films (비정량적 산화티타늄 박막의 상변태 특성)

  • Hong, Seong-Min;Lee, Pil-Hong;Go, Gyeong-Hyeon;An, Jae-Hwan;Lee, Sun-Il
    • Korean Journal of Materials Research
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    • v.8 no.3
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    • pp.224-228
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    • 1998
  • Phase transition kinetics of nonstoichiometric amorphous titanium oxide thin films deposited by reactive sputtering was investigated after cooling down with various rate followed by l0min.-3hrs. annealing at $500^{\circ}C$~$600^{\circ}C$ After short duration and fast cooling. Magneli was the only crystalline phase because the oxidation rates of $TiO_{2-x}$, could be relatively slower than that of crystallization. When the films were cooled slowly between $500^{\circ}C$~$300{\circ}C$, Magneli was transformed into an anatase and stabilized, but directly into a rutile under fast cooling. Because the rutile also prevailed after cooling from $600^{\circ}C$, it was concluded that the rutile phase could be formed directly from Magneli as well as converted from the anatase. Changes in volume and surface morphology were observed related to crystallization and oxidation processduring heat treatment.

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Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Cr(VI)-4,4'-Bipyridine Complex (크롬(VI)-4,4'-Bipyridine 착물에 의한 치환 벤질 알코올류의 산화반응 속도론과 메카니즘)

  • Kim, Young-Sik;Park, Young-Cho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.1
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    • pp.462-469
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    • 2012
  • Cr(VI)-4,4'-bipyridine complex(4,4'-bipyridinium dichromate) was synthesized by the reaction of 4,4'-bipyridine with chromium trioxide in H2O, and characterized by IR, ICP. The oxidation of benzyl alcohol using 4,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene$CH_3$, H, m-Br, m-$NO_2$) smoothly in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.63(303K). The observed experimental data have been rationalized as follows; the proton transfer occurs after the prior formation of a chromate ester in the rate determining step.

Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Cr(VI)-Heterocyclic Complex (2,4'-Bipyridinium Chlorochromate) (크롬(VI)-헤테로고리 착물(2,4'-비피리디늄 클로로크로메이트)에 의한 치환 벤질 알코올류의 산화반응에서 속도론과 메카니즘)

  • Park, Young Cho;Kim, Young Sik
    • Applied Chemistry for Engineering
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    • v.25 no.6
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    • pp.648-653
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    • 2014
  • Cr(VI)-heterocyclic complex (2,4'-bipyridinium chlorochromate) was synthesized by the reaction between heterocyclic compound(2,4'-bipyridine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium chlorochromate in various solvents showed that the reactivity increased with the increase of the dielectric constant (${\varepsilon}$), in the order : N,N-dimet-hylformamide (DMF) > acetone > chloroform > cyclohexene. In the presence of DMF solvent with acidic catalyst such as hydrochloric acid (HCl solution), 2,4'-bipyridinium chlorochromate oxidized benzyl alcohol (H) and its derivatives (p-$CH_3$, m-Br, m-$NO_2$). Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.67 (303 K). The observed experimental data have been rationalize the proton transfer occurred followed the formation of a chromate ester in the rate-determining step.

Methane Partial Oxidation Using Cu-ferrite (Cu-ferrite에 의한 메탄의 부분산화)

  • Woo, Sung-Woung;Kang, Kyoung-Soo;Kim, Chang-Hee;Park, Chu-Sik
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.2
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    • pp.124-131
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    • 2007
  • Methane is partially oxidized to produce the syngas by the lattice oxygen of metal oxides in the absence of gaseous oxygen. The present work deals with ferrite including copper component, which does not chemisorb methane, to investigate the suppression of the carbon deposition during the reduction of metal oxides by methane. Iron-based oxides of $Cu_xFe_{3-x}O_4$(X=0.25, 0.5, 1.0) was synthesized by the co-precipitation method. Thermogravimetric Analysis(TGA) was used to observe the isothermal reduction behavior of $Cu_xFe_{3-x}O_4$ and $Fe_3O_4$ at $600-900^{\circ}C$ under methane atmosphere. The crystal structures of reduced specimens were characterized by X-rays powder diffraction(XRD) technique. From the analyses of TGA, it is concluded that the reduction kinetics of $CuFe_2O_4$ was the fastest among $Fe_3O_4$ and $Cu_xFe_{3-x}O_4$(X=0.25, 0.5, 1.0). The X-ray diffraction analyses indicated that $Cu_xFe_{3-x}O_4$ was decomposed to Cu and $Fe_3O_4$ phase at $600^{\circ}C$ and was reduced to Cu and Fe phase at $800^{\circ}C$. $Fe_3O_4$, which was reduced at $900^{\circ}C$, showed Fe, graphite and $Fe_3C$ phases. On the contrary, $Cu_xFe_{3-x}O_4$ does not show the graphite or $Fe_3C$ phases. This results infer that Cu component suppress the carbon deposition on Cu-ferrite.

Electrocatalytic Oxidation of NADH at the Modified Graphite Electrode Incorporating Gold Nano Particles (금 나노입자를 회합시킨 수식된 흑연전극으로 NADH의 전기촉매 산화반응)

  • Cha, Seong-Keuck;Han, Sung-Yub
    • Journal of the Korean Electrochemical Society
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    • v.10 no.1
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    • pp.1-6
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    • 2007
  • Mercaptopropionic acid(mpa) has been used to make self-assembled monolayer(SAMs) on the surface of graphite electrode incorporating gold nano particles, which are subsequently modified with dopamine(dopa). Such modified electrodes haying types of Gr(Au)/mpa-dopa were employed in the electrocatalytic oxidation of NADH. The responses of such modified electrodes were studied in terms of electron transfer kinetics and reaction procedure in the reaction. The reaction of the surface immobilized dopa with NADH was studied using the rotating disk electrode technique and a value of $5.06{\times}10^5M^{-1}s^{-1}$ was obtained for the second-order rate constant in 0.1 M phosphate buffer(pH=7.0), which was a $EC_{cat}$ and kinetic controlled procedure. But, the modified electrodes were diffusion controlled reaction having $4.64{\times}10^{-4}cm^2s^{-1}$ of the coefficient within $10^{-3}s$ after starting the reaction.

Studies on decomposition behavior of oxalic acid waste by UVC photo-Fenton advanced oxidation process

  • Kim, Jin-Hee;Lee, Hyun-Kyu;Park, Yoon-Ji;Lee, Sae-Binna;Choi, Sang-June;Oh, Wonzin;Kim, Hak-Soo;Kim, Cho-Rong;Kim, Ki-Chul;Seo, Bum-Chul
    • Nuclear Engineering and Technology
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    • v.51 no.8
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    • pp.1957-1963
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    • 2019
  • A UVC photo-Fenton advanced oxidation process (AOP) was studied to develop a process for the decomposition of oxalic acid waste generated in the chemical decontamination of nuclear power plants. The oxalate decomposition behavior was investigated by using a UVC photo-Fenton reactor system with a recirculation tank. The effects of the three operational variables-UVC irradiation, H2O2 and Fenton reagent-on the oxalate decomposition behavior were experimentally studied, and the behavior of the decomposition product, CO2, was observed. UVC irradiation of oxalate resulted in vigorous CO2 bubbling, and the irradiation dose was thought to be a rate-determining variable. Based on the above results, the oxalate decomposition kinetics were investigated from the viewpoint of radical formation, propagation, and termination reactions. The proposed UVC irradiation density model, expressed by the first-order reaction of oxalate with the same amount of H2O2 consumption, satisfactorily predicted the oxalate decomposition behavior, irrespective of the circulate rate in the reactor system within the experimental range.

Kinetics of the Oxidation of Substituted Benzyl Alcohols using 6-Methylquinolinium Dichromate (6-Methylquinolinium Dichromate를 이용한 치환 벤질 알코올류의 산화반응 속도)

  • Kim, Young-Sik;Park, Young-Cho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.12
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    • pp.5990-5996
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    • 2011
  • 6-Methylquinolinium dichromate[$(C_{10}H_9NH)_2Cr_2O_7$] was synthesized by the reaction of 6-methylquinoline with chromium trioxide in $H_2O$, and characterized by IR, ICP. The oxidation of benzyl alcohol using 6-methylquinolinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene < chloroform < acetone < N,N- dimethylformamide. In the presence of hydrochloric acid($H_2SO_4$ solution), 6-methylquinolinium dichromate oxidized benzyl alcohol and its derivatives(p-$OCH_3$, m-$CH_3$, H, m-$OCH_3$, m-Cl, m-$NO_2$) smoothly in DMF. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.67(303K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

DTNB oxidation effects on T-type $Ca^{2+}$ channel isoforms

  • Lee, Sang-Soo;Kang, Ho-Won;Park, Jin-Yong;Lee, Jung-Ha
    • Animal cells and systems
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    • v.15 no.2
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    • pp.131-138
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    • 2011
  • Redox regulation is one of the ubiquitous mechanisms to modulate ion channels. We here investigated how 5,5'-dithio-bis (2-nitrobenzoic acid), a cysteine specific oxidizing reagent, modulates $Ca_v3.1$ and $Ca_v3.2$ T-type $Ca^{2+}$ channels expressed in Xenopus oocytes. Application of the reagent inhibited $Ca_v3.1$ and $Ca_v3.2$ currents in a dose-dependent manner. The oxidizing reagent (1 mM) reduced the peak amplitude of $Ca_v3.1$ and $Ca_v3.2$ currents by ~50% over 2-3 minutes and the decreased currents were fully recovered upon washout of it. The reagent slowed the activation and inactivation kinetics of $Ca_v3.1$, $Ca_v3.2$, and $Ca_v3.3$ channel currents. Notably, the reagent positively shifted both activation and steady-state inactivation curves of $Ca_v3.1$, while it did not those of $Ca_v3.2$. Utilizing chimeric channels from $Ca_v3.1$ and $Ca_v3.2$, we localized the domains III and IV of $Ca_v3.1$ responsible for the positive shifts of channel activation and steady-state inactivation. These findings provide hints relevant to the electrophysiological and molecular mechanisms accounting for the oxidative regulation of T-type channels.

A Study for Kinetics and Oxidation Reaction of Substituted Benzyl Alcohols Using 2,4'-Bipyridinium Dichromate (2,4'-Bipyridinium Dichromate를 이용한 치환 벤질 알코올류의 산화반응과 반응속도에 관한 연구)

  • Kim, Young Sik;Park, Young Cho
    • Applied Chemistry for Engineering
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    • v.22 no.6
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    • pp.718-722
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    • 2011
  • 2,4'-Bipyridinium dichromate [$(C_{10}H_8N_2H)_2Cr_2O_7$] was synthesized by the reaction of 2,4'-bipyridinie with chromium trioxide in $H_2O$. The structure was characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase in the order of the dielectric constant (${\varepsilon}$), in the order : cyclohexene < chloroform < acetone < N,N'-dimethylformamide. In the presence of hydrochloric acid, 2,4'-bipyridinium dichromate effectively oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) in N,N'-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant (${\rho}$) was -0.65 at 303 K. The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.