• Title, Summary, Keyword: Chemical Speciation

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Evaluation of effect of rapid mixing intensity on chemical phosphorus removal using Al hydrolysis speciation (가수분해 산물 분포를 이용한 급속혼화강도가 화학적 인 제거 효율에 미치는 영향의 규명)

  • Kim, Seung-Hyun;Yoon, Dong-Soo;Moon, Byung-Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.25 no.3
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    • pp.367-373
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    • 2011
  • Mechanism of rapid mixing effect on chemical phosphorus removal is evaluated in this study. Assuming that chemical phosphorus removal is unaffected by mixing time, only rapid mixing intensity is evaluated. In order to find out the mechanism, it is hypothesized that rapid mixing affects the Al hydrolysis speciation, and that formation of more monomeric species ($Al^a$) results in better removal of phosphorus. According to a ferron assay, more $Al^a$ formed at higher mixing intensity than at lower intensity. Subsequent experiments revealed that better phosphorus removal was obtained at higher intensity than at lower intensity, in terms of the molar ratio of $Al_{added}/P_{removed}$. The proposed hypothesis was proved in this study. Chemical phosphorus removal is affected by rapid mixing intensity due to its effect on the Al hydrolysis speciation.

Comparison of chemical and photochemical generation of hydrides in Se speciation study with HPLC-HG-ICPMS (HPLC-ICPMS를 이용한 셀레늄 화학종의 연구에서 화학적 및 광화학적 수소화물 발생법의 비교)

  • Ji, Hana;Pak, Yong-Nam
    • Analytical Science and Technology
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    • v.25 no.6
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    • pp.339-344
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    • 2012
  • In this research, hydride generation in HPLC-ICPMS for the selenium speciation was investigated. Chemical and photochemical vapor generation techniques were compared for the effective generation of selenium vapour. $HBr/KBrO_3$ was used for the chemical reduction and a UV lamp was used for the photochemical reduction. It was found out that the photochemical reduction was more effective than the chemical reduction in all of selenium species studied. The optimum conditions for the generation of vapour are 0.4% KI, 2.5% $NaBH_4$, and 1.0 M HCl. The enhancement factor using a photochemical hydride generation was from 6.3 to 16.7 times for inorganic and organic selenium species.

Estimation of Chemical Speciation and Temporal Allocation Factor of VOC and PM2.5 for the Weather-Air Quality Modeling in the Seoul Metropolitan Area (수도권 지역에서 기상-대기질 모델링을 위한 VOC와 PM2.5의 화학종 분류 및 시간분배계수 산정)

  • Moon, Yun Seob
    • Journal of the Korean earth science society
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    • v.36 no.1
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    • pp.36-50
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    • 2015
  • The purpose of this study is to assign emission source profiles of volatile organic compounds (VOCs) and particulate matters (PMs) for chemical speciation, and to correct the temporal allocation factor and the chemical speciation of source profiles according to the source classification code within the sparse matrix operator kernel emission system (SMOKE) in the Seoul metropolitan area. The chemical speciation from the source profiles of VOCs such as gasoline, diesel vapor, coating, dry cleaning and LPG include 12 and 34 species for the carbon bond IV (CBIV) chemical mechanism and the statewide air pollution research center 99 (SAPRC99) chemical mechanism, respectively. Also, the chemical speciation of PM2.5 such as soil, road dust, gasoline and diesel vehicles, industrial source, municipal incinerator, coal fired, power plant, biomass burning and marine was allocated to 5 species of fine PM, organic carbon, elementary carbon, $NO_3{^-}$, and $SO_4{^2-}$. In addition, temporal profiles for point and line sources were obtained by using the stack telemetry system (TMS) and hourly traffic flows in the Seoul metropolitan area for 2007. In particular, the temporal allocation factor for the ozone modeling at point sources was estimated based on $NO_X$ emission inventories of the stack TMS data.

Speciation of Cr(III)/Cr(VI) in Tannery Waste Waters by Using Ion-Exchange Resins

  • Kartal, S.;Tokalloglu, S.;Ozkan, B.
    • Bulletin of the Korean Chemical Society
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    • v.27 no.5
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    • pp.694-698
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    • 2006
  • A method has been described for the chemical speciation, preconcentration and determination of Cr(III) and Cr(VI) species in filtered tannery waste waters by flame atomic absorption spectrometry using ion-exchange resins. Amberlite IR-120($H^+$) strongly acidic cation exchanger and Amberlite IRA-410($CI ^-$) strongly basic anion exchanger resins were used for the separation and preconcentration of Cr(III) and Cr(VI) species, respectively. Optimum condition for preconcentration and speciation was obtained by testing pH of sample and eluent, flow rates of sample and eluent, amount of resins, volume of sample and eluents, and effect of foreign ions. The recommended method has been successfully applied for the preconcentration and determination of chromium species in the dissolved phase of waste water samples collected from a tannery waste water treatment plant in Kayseri, Turkey. The detection limits achieved were 0.73 $\mu$g/L for Cr(III) and 0.81 $\mu$g/L for Cr(VI). Recovery studies showed 99% for Cr(III) and 98% for Cr(VI), for samples spiked with single species.

Study on the Chemical Speciation of Hydrolysis Compounds of U(VI) by Using Time-Resolved Laser-Induced Fluorescence Spectroscopy (시간분해 레이저 유도 형광 분광학을 이용한 우라늄(VI) 가수분해 화학종 규명 연구)

  • Jung, Euo-Chang;Cho, Hye-Ryun;Park, Kyoung-Kyun
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.7 no.3
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    • pp.133-141
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    • 2009
  • Study on the chemical speciation of uranium(VI) species, ${UO_2}^{2+}$, $UO_2(OH)^+$, ${(UO_2)}_2{(OH)_2}^{2+}$, ${(UO_2)}_3{(OH)_5}^+$, has been peformed by using time-resolved laser-induced fluorescence spectroscopy. Speciation sensitivity which depends on the excitation wavelength was investigated. We obtained the speciation sensitivity in the order of $10^{-9}$ M concentration of U(VI) compounds at the excitation wavelength of 266 nm. The fluorescence spectrum and lifetime of ${UO_2}^{2+}$ were carefully measured at pH 1 and ion strength of 0.1 M. The spectrum showed the four characteristic peaks located around 488, 509, 533, 559nm and the fluorescence lifetime of $1.92{\pm}0.17{\mu}s$. The wavelength shifts of fluorescence peaks and the change of lifetimes for uranium hydrolysis compounds were compared with those of ${UO_2}^{2+}$. We report on the characteristic features, the shifts of peaks to the longer wavelength direction and the prolonged lifetimes, in the fluorescence of the U(VI) hydrolysis compounds.

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Assessment of Changed Input Modules with SMOKE Model (SMOKE 모델의 입력 모듈 변경에 따른 영향 분석)

  • Kim, Ji-Young;Kim, Jeong-Soo;Hong, Ji-Hyung;Jung, Dong-Il;Ban, Soo-Jin;Lee, Yong-Mi
    • Journal of Korean Society for Atmospheric Environment
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    • v.24 no.3
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    • pp.284-299
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    • 2008
  • Emission input modules was developed to produce emission input data and change some profiles for Sparse Matrix Operator Kernel Emissions (SMOKE) using Clean Air Policy Support System (CAPSS)'s activities and previous studies. Specially, this study was focused to improve chemical speciation and temporal allocation profiles of SMOKE. At first, SCC cord mapping was done. 579 SCC cords of CAPSS were matched with EPA's one. Temporal allocation profiles were changed using CAPSS monthly activities. And Chemical speciation profiles were substituted using Kang et al. (2000) and Lee et al. (2005) studies and Kim et al. (2005) study. Simulation in Seoul Metropolitan Area (Seoul, Incheon, Gyeonggi) using MM5, SMOKE and CMAQ modeling system was done for effect analysis of changed input modules of SMOKE. Emission model results adjusted with new input modules were slightly changed as compared to using EPA's default modules. SMOKE outputs shows that aldehyde emissions were decreased 4.78% after changing chemical profiles, increased 0.85% after implementing new temporal profiles. Toluene emissions were decreased 18.56% by changing chemical speciation profiles, increased 0.67% by replacing temporal profiles as well. Simulated results of air quality were also slightly elevated by using new input modules. Continuous accumulation of domestic data and studies to develop input system for air quality modeling would produce more improved results of air quality prediction.

Chemical Equilibrium Modeling for Magnetite-Packed Crevice Chemistry in a Nuclear Steam Generator

  • Bahn, Chi-Bum;Rhee, In-Hyoung;Hwang, Il-Soon;Park, Byung-Gi
    • Bulletin of the Korean Chemical Society
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    • v.26 no.11
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    • pp.1783-1789
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    • 2005
  • Modeling of a steam generator crevice in a nuclear power system needs to take into account both thermalhydraulic and chemical phenomena. As a first step towards developing a reliable model, a chemical equilibrium model was developed to predict chemical speciation in a magnetite-packed crevice by adopting the “tableau” method. The model was benchmarked with the available experimental data and the maximum deviation did not exceed two orders of magnitude. The developed model was applied to predict the chemical speciation in a magnetite-packed crevice. It was predicted that caustic environment was developed by the concentration of NaOH and the dissolution of magnetite. The model indicated that the dominant aqueous species of iron in the caustic crevice was $FeO_2\;^-$. The increase of electrochemical corrosion potential observed in the experiment was rationalized by the decrease of dissolved hydrogen concentration due to a boiling process. It was predicted that under the deaerated condition magnetite was oxidized to hematite.

Chemical Speciation of Trace Metals in Natural Water by Ultrafiltration/Size Exclusion Chromatography/UV Absorption/ICP-MS

  • Haraguchi, Hiroki;Itoh, Akihide;Kimata, Chisen
    • Analytical Science and Technology
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    • v.8 no.4
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    • pp.405-410
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    • 1995
  • A study on elemental speciation of trace metals in lake water (Lake Biwa in Japan) has been carried out by a size exclusion chromatography (SEC) / inductively coupled plasma mass spectrometry (ICP-MS) system. Before analysis, the water sample was preconcentrated with a ultrafiltration technique, where the large molecules with molecular weight larger than 10,000 were concentrated. Then the preconcentrated water samples (500-1000 fold) were analyzed by a SEC/ICP-MS system. Most trace metals were found at the UV absorption peaks corresponding to the molecular weights of ca. 300,000 and 10,000-50,000, where trace metals were on-line detected by ICP-MS. The results suggest that many of trace metals exist as the large organic molecules-metal complexes in natural water.

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