• Title/Summary/Keyword: 화학종

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Electrochemical Rectification at Electrode Chemically Modified with Redox Active Agents at Monolayer (산화환원 화학 종이 단 분자 층으로 화학 흡착된 전극에서의 전기화학적 정류)

  • Lee, Chi-Woo J.;Yoon, Jung-Hyun;Oh, Mi-Kyung
    • Journal of the Korean Electrochemical Society
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    • v.10 no.1
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    • pp.43-47
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    • 2007
  • Electrochemical rectification at electrode chemically modified with redox active agents isolated at monolayer level was considered. Formulation of the rising part of linear sweep voltammogram at steady and rotating disc electrode was introduced.

Study on the Species Distributions of Dissolved U(VI) and Adsorbed U(VI) on Silica Surface (용존 6가 우라늄 및 실리카 표면 흡착 6가 우라늄 화학종 분포 연구)

  • Jung, Euo Chang;Kim, Tae-Hyeong;Jo, Yongheum;Kim, Hee-Kyung;Cho, Hye-Ryun;Cha, Wansik;Baik, Min Hoon;Yun, Jong-Il
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.1
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    • pp.63-72
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    • 2020
  • Dissolved hexavalent uranium can exist in the form of several different chemical species. Furthermore, species distributions depend on the pH value of the aqueous solution. Representatively, UO22+, UO2OH+, (UO2)2(OH)22+, and (UO2)3(OH)5+ species coexist in solutions at acidic and circumneutral pH values. When amorphous silica particles are suspended in an aqueous solution, the dissolved chemical species are easily adsorbed onto silica surfaces. In this study, it was examined whether the species distribution of the adsorbed U(VI) on a silica surface followed that of the dissolved U(VI) in an aqueous solution. Time-resolved luminescence spectra of three different dissolved species (UO22+, UO2OH+, and (UO2)3(OH)5+) and two different adsorbed species (≡SiO2UO2, ≡SiO2(UO2)OH-, or ≡SiO2(UO2)3(OH)5-) were measured in the pH range 3.5-7.5. The spectral shapes of these chemical species were compared by changing the pH value; consequently, it was confirmed that the species distribution of the adsorbed U(VI) species was different from that of the dissolved U(VI) species.

Analysis of Rock Surface Roughness and Chemical Species Generation by Freeze-Thaw Experiments (동결융해 실험을 통한 암석 표면 거칠기 및 화학종 생성에 관한 분석)

  • Choi, Junghae
    • Korean Journal of Mineralogy and Petrology
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    • v.35 no.3
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    • pp.299-311
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    • 2022
  • Rocks exposed to the surface are subject to long-term weathering, and such effects weaken their engineering stability. Especially as weathering progresses, the surface of rocks will be changed by weathering, and such surface changes will affect the engineering safety of the rock mass. In addition, the chemical species produced in the weathered rock have a direct effect on the surrounding environment or on the structure. In areas where rocks are exposed, such as mining areas, chemical species produced by weathering can have a serious impact on the surrounding natural environment. In this study, accelerated weathering experiments using freeze/thaw system were conducted on rocks that had already been weathered and fresh rocks, and surface changes of each rock were observed with confocal laser scanning microscope (CLSM), and chemical species were analyzed using IC/ICP-MS. As the weathering progressed, the surface roughness decreased, and the amount of chemical species produced increased. The results of this study can be used as basic data for evaluating engineering/environmental safety in areas where rocks are exposed.

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.

Study on Mo(V) Species, Location and Adsorbates Interactions in MoH-SAPO-34 by Employing ESR and Electron Spin-Echo Modulation Spectroscopies (ESR, ESEM을 이용한 이온 교환된 MoH-SAPO-34에 대한 Mo의 화학종, 위치 및 흡착상호작용에 관한 연구)

  • Back, Gern-Ho;Jang, Chang-Ki;Ru, Chang-Kuk;Cho, Young-Hwan;So, Hyun-Soo;Kevan, Larry
    • Journal of the Korean Chemical Society
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    • v.46 no.1
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    • pp.26-36
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    • 2002
  • A solid-state reaction of $MoO_3$ with as-synthesized H-SAPO-34 generated paramagnetic Mo(V) species. The dehydration resulted in weak Mo(V) species, and subsequent activation resulted in the formation of Mo(V) species such as $Mo(V)_{5c}$ and $Mo(V)_{6c}$ that are characterized by ESR. The data of ESR and ESEM show the oxomolybdenum species, to be $(MoO_2)^+$ or $(MoO)^{3+}$. The $(MoO_2)^+$ species seems to be more probable. Since H-SAPO-34 has a low framework negative charge, $(MoO)^{3+}$ with a high positive charge can not be easily stabilized. A solution reaction between the solution of silico-molybdic acid and calcined H-SAPO-34 resulted in only $(MoO_2)^+$ species. A rhombic ESR signal is observed on adsorption of $D_2O$, $CD_3OH$, $CH_3Ch_2OD$ and $ND_3$. The Location and coordination structure of Mo(V) species has been determined by three-pulse electron spin-echo modulation data and their simulations. After the adsorption of methanol, ethylene, ammonia, and water for MoH-SAPO-34, three molecules, one molecule, one and one molecule, respectively, are directly coordinated to $(MoO_2)^+)$.

Study on the Interaction of U(VI) Species With Natural Organic Matters in KURT Groundwater (KURT 지하수의 천연 유기물질과 6가 우라늄 화학종의 상호작용에 관한 연구)

  • Jung, Euo Chang;Baik, Min Hoon;Cho, Hye-Ryun;Kim, Hee-Kyung;Cha, Wansik
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.15 no.2
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    • pp.101-116
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    • 2017
  • The interaction of U(VI) (hexavalent uranium) species with natural organic matter (NOM) in KURT (KAERI Underground Research Tunnel) groundwater is investigated using a laser spectroscopic technique. The luminescence spectra of the NOM are observed in the ultraviolet and blue wavelength regions by irradiating a laser beam at 266 nm in groundwater. The luminescence spectra of U(VI) species in groundwater containing uranium concentrations of $0.034-0.788mg{\cdot}L^{-1}$ are measured in the green-colored wavelength region. The luminescence characteristics (peak wavelengths and lifetime) of U(VI) in the groundwater agree well with those of $Ca_2UO_2(CO_3)_3(aq)$ in a standard solution prepared in a laboratory. The luminescence intensities of U(VI) in the groundwater are weaker than those of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution at the same uranium concentrations. The luminescence intensities of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution mixed with the groundwater are also weaker than those of $Ca_2UO_2(CO_3)_3(aq)$ in the standard solution at the same uranium concentrations. These results can be ascribed to calcium-U(VI)-carbonate species interacting with NOM and forming non-radiative U(VI) complexes in groundwater.

Studies of separation and quantitation for selenium species in food (식품중의 셀레늄 화학종의 분리 및 정량연구)

  • Jang, Hee-Young;Min, Hyungsik;Lee, Jonghae;Pak, Yong-Nam
    • Analytical Science and Technology
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    • v.26 no.3
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    • pp.182-189
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    • 2013
  • The purpose of this research is to separate and quantitate selenium species in some food samples with HPLC-ICP-MS. Cation exchange chromatography showed efficient separation only for inorganic Se species while reversed phase ion pair chromatography showed good separation for both inorganic and organic Se species. $C_8$ column ($Symmetryshield^{TM}\;RP_8$, 3.5 ${\mu}m$, $4.6{\times}150$ mm) was used with optimum condition of 5% methanol mobile phase, 0.05% of nonafluorovaleric acid ion pairing reagent. Five standard Se species of Se(IV), Se(VI), SeCys(selenocystein), SeMet(selenomethionine) and Se-M-C(seleno methyl cystein) were separated successfully under the optimum condition (mobile phase; 5% methanol, ion-pairing reagent; 0.05% nonafluorovaleric acid, flow rate; 0.9 mL $min^{-1}$). To extract Se species, microwave assisted and enzyme-assisted extraction methods were studied. In enzyme-assisted extraction method, protease I for garlic, protease I plus trypsin for pork and mackerel, and protease XIV for tuna showed the best extraction efficiency. With the optimum condition for each sample, it was found that mostly inorganic Se, SeCys and SeMet are present in the sample studied ranging from few ${\mu}g$ $g^{-1}$ to few tens of ${\mu}g$ $g^{-1}$.

Synergistic Effect of Ethylene-Propane Mixture on Soot Formation in Counterflow Diffusion Flame (대향류 확산 화염에서 에틸렌-프로판 혼합 연료의 매연 생성 상승 효과)

  • Hwang, Jun-Yeong;Jeong, Seok-Ho
    • 한국연소학회:학술대회논문집
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    • 1997.06a
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    • pp.89-102
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    • 1997
  • 대향류 확산 화염의 매연 생성 특성에 대한 실험적 연구가 수행되었으며, 그 결과 에틸렌 ($C_2H_4$)-프로판($C_3H_8$) 혼합 연료의 경우 매연 생성 상승 효과 (synergistic effect)가 관측되었다. 프로판과 에틸렌의 PAH 생성 양상이 상이하게 나타났으며, 소량의 프로판을 에틸렌 확산 화염에 첨가할 경우 순수 연료에 비하여 매연 및 PAH (다중 고리 방향족 탄화수소; polycyclic aromatic hydrocarbon) 생성이 증대되었다. 단조적으로 변화하는 아세틸렌($C_2H_2$) 농도와 단열 화염 온도를 고려할 때, 이러한 결과는 HACA (H-abstraction-$C_2H_2$-addition) 반응만으로는 확산 화염에서의 매연 발생 및 성장을 설명할 수 없음을 의미한다. 수치해석과 실험 결과의 비교로부터 초기 PAH의 생성 과정을 규명하였으며 이 과정에서 C3 화학종의 재결합 반웅이 매우 중요함을 확인할 수 있었다. 또한, 이러한 C3 화학종과 C2 화학종의 상호 보완적인 역할에 의하여 에틸렌-프로판 혼합 연료에서 매연 생성이 증대됨을 밝혔다.

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Comparative Degumming Effects of Detergents on Silk Twill (견직물에 대한 화학정련제의 정련효과 비교연구)

  • ;A.B
    • Journal of Sericultural and Entomological Science
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    • v.29 no.1
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    • pp.57-63
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    • 1987
  • 견직물의 정련에 있어서 관행 정련제인 비누와 이태리 견직업계에서 사용하고 있는 3종의 화학정련제를 비교 시험하였다. 정련 견직물의 강신도와 염색성은 비누 정련과 화학정련제 간에 차이가 없었으나 견직유질의 변성과 관련되는 점도 및 아미노기(-NH2) 함량은 비누정련견이 화학정련제 정련견에 비하여 약간 증가 및 감소되었으며 표면 미세구조에 있어서도 비누 정련견이 비교적 불순물의 잔류가 적었고 3종의 화학정련제 중에서는 정련제 "S"에 의한 정련견에 불순물의 잔류가 가장 적게 보였다.가장 적게 보였다.

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An Axisymmetrical Study on the Secondary Reaction of Launch Vehicle Turbine Exhaust Gas Using the Detailed Chemistry Model (상세 화학반응 모델을 이용한 발사체 터빈 배기가스의 이차연소 해석의 축대칭 해석)

  • Kim, Seong-Lyong;Kim, In-Sun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.857-862
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    • 2011
  • 3 dimensional turbine exhaust gas flow was simplified to an axisymmetrical flow and calculated with detailed chemistry models. GRI 35 species-217 reaction step model and simplified 11 species 15 reaction model was applied to the secondary reaction of the turbine exhaust gas and compared. All the model captured the secondary combustion on the base region, and the temperature was 600K higher than that without turbine exhaust gas. This means the local temperature of the base can be higher in the case of real 3 dimensional flow. The simplified model show the similar results to the GRI detailed chemistry model although the former affected the engine plume structure slightly.

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