• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2539-2545
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• 2012

In the present study, we suggest a new way to reactivate performance of direct formic acid fuel cell (DFAFC) and explain its mechanism by employing electrochemical analyses like chronoamperometry (CA) and cyclic voltammogram (CV). For the evaluation of DFAFC performance, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane spraying. After long DFAFC operation performed at 0.2 and 0.4 V and then CV test, DFAFC performance is better than its initial performance. It is attributed to dissolution of anode Pd into $Pd^{2+}$. By characterizations like TEM, Z-potential, CV and electrochemical impedance spectroscopy, it is evaluated that such dissolved $Pd^{2+}$ ions lead to (1) increase in the electrochemically active surface by reduction in Pd particle size and its improved redistribution and (2) increment in the total oxidation charge by fast reaction rate of the Pd dissolution reaction.

• 한국산업융합학회 논문집
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• 제15권3호
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• pp.71-77
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• 2012

This study gives the optimal reaction conditions, reaction mechanisms, reaction rates leaded from the oxidation of phenol by electron beam accelerator and ozone used for recent water treatment. It gives the new possibility of water treatment process to effectively manage industrial sewage containing toxic organic compounds and biological refractory materials. The high decomposition of phenol was observed at the low dose rate, but at this low dose rate, the reaction time was lengthened. So we must find out the optimal dose rate to promote high oxidation of reactants. The reason why the TOC value of aqueous solution wasn't decreased at the low dose was that there were a lot of low molecular organic acids as an intermediates such as formic acid or glyoxalic acid. In order to use both electron beam accelerator and biological treatment for high concentration refractory organic compounds, biological treatment is needed when low molecular organic compounds exist abundantly in sewage. In this experiment, the condition of making a lot of organic acids is from 5 kGy into 20 kGy dose. Decomposition rate of phenol by electron beam accelerator was first order reaction up to 300ppm phenol solution on the basic of TOC value and also showed first order reaction by using both air and ozone as an oxidants.

• 상하수도학회지
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• 제25권5호
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• pp.643-649
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• 2011

Degradation of benzothiophene(BT) in the aqueous phase by potassium ferrate(VI) was investigated. Potassium ferrate(VI) was prepared by the wet oxidation method. The degradation efficiency of BT was measured at various values of pH, ferrate(VI) dosage and initial concentration of BT. BT was degraded rapidly within 30 seconds by ferrate(VI). While the highest degradation efficiency was achieved at pH 5, the lowest degradation efficiency was achieved at pH 9. Also, the initial rate constant of BT increased with decreasing of the BT initial concentration. In addition, the intermediate analysis for the reaction of BT and ferrate(VI) has been conducted using GC-MS. Benzene, styrene, benzaldehyde, formaldehyde, benzoic acid, formic acid, and acetic acid were identified as reaction intermediates, and ${SO_4}^{2-}$ was identified as an end product.

• 전기화학회지
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• 제24권4호
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• pp.113-119
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• 2021

본 연구에서는 유기환원제로 포름산과 촉매로 PtD/C를 사용하여 불순물이 없는 고품질 V^3.5+ 전해질을 생산하였고 이를 VRFB에 적용하였다. PtD/C 촉매의 잘 배향된 3D 수상 돌기 구조는 포름산 산화 반응과 바나듐 환원 반응에 높은 활성을 보여 주었다. 그 결과 PtD/C의 촉매 전환율은 2.73 mol g^-1 h^-1로 polyol방법을 제조된 Pt/C의 전환율 1.67 mol g^-1 h^-1보다 더 높았다. 또한 VRFB 충방전 실험에서 촉매 반응으로 생성된 V^3.5+ 전해질은 전해 방법으로 제조 된 표준V^3.5+전해질과 동일한 성능을 보여 줌으로서 VRFB의 전해질로 사용 가능함을 증명하였다.

• 상하수도학회지
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• 제25권1호
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• pp.63-74
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• 2011

The degradation characteristics of 2-chlorophenol(2-CP) by Ferrate(VI) were studied. The degradation efficiency of 2-CP in aqueous solution was investigated at various values of pH, Fe(VI) dosage, initial concentration and aqueous solution temperature. The maximum degradation efficiencies of 2-CP were obtained at pH 7.0 and aqueous solution temperature of 25$^{\circ}C$. The degradation efficiency was proportional to dosage of Fe(VI). Also, the initial rate constant of 2-CP degradation increased with decreasing of the 2-CP initial concentration. In addition, the degradation pathway study for 2-CP was conducted with GC-MS analysis. Acetic acid, formic acid, benzaldehyde and benzoic acid were identified as reaction intermediates of the 2-CP degradation by Ferrate(VI).

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.316-319
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• 2006

There is a worldwide interest in the development and commercialization of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the deposition of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an at toying process occurred during the successive reducing process The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one (Johnson-Matthey) for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

• 신재생에너지
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• 제2권4호
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• pp.64-69
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• 2006

There is a worldwide interest in the development and commercialization of polymer electrolyte membrane fuel cells [PEMFCs] for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the supporting of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an alloying process occurred during the successive reducing process. The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one [Johnson-Matthey] for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

• Korean Chemical Engineering Research
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• 제47권3호
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• pp.292-302
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• 2009

페놀 습식산화에 미치는 반응온도($150{\sim}250^{\circ}C$), 산소분압(25.8~75.0 bar) 및 초기 pH(1.0~12.0)의 영향을 10 g/l의 페놀 초기농도를 사용하여 조사하였다. 습식산화속도는 화학적 산소요구량 COD를 이용하여 산출하였으며 반응 중간 생성물들을 고성능액체크로마토그래피를 사용하여 측정하였다. 습식산화 중 페놀 분해속도는 페놀에 대하여 1차 반응차수를 나타냈으며, COD 변화는 lumped 모델로 잘 묘사할 수 있었다. 금속이온($Cu^{2+}$, $Fe^{2+}$, $Zn^{2+}$, $Co^{2+}$, $Ce^{3+}$) 균일촉매의 습식산화 중 페놀 분해속도 및 COD 제거속도에 미치는 영향도 조사하였다. 페놀 분해속도 및 COD 제거속도는 $CuSO_4$를 사용한 촉매습식산화에서 가장 크게 나타났으며 촉매농도를 증가시킴에 따라 증가하였다. 습식산화 중 생성되는 개미산의 분해속도는 반응온도 및 $CuSO_4$ 농도를 증가시킴에 따라 증가하였다. 난분해성 생성물 초산의 최종농도는 반응온도를 증가시킴에 따라 증가하였으나 $CuSO_4$ 농도를 증가시킴에 따라 감소하였다.

• Asian Journal of Atmospheric Environment
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• 제11권4호
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• pp.300-312
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• 2017

To improve the understanding of secondary organic aerosol (SOA) formation from the photo-oxidation of anthropogenic and biogenic precursors at the regional background station on Baengnyeong Island, Korea, gas phase and aerosol chemistries were investigated using the Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS) and the Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), respectively. HR-ToF-AMS measured fine particles ($PM_1$; diameter of particle matter less than $1{\mu}m$) at a 6-minute time resolution from February to November 2012, while PTR-ToF-MS was deployed during an intensive period from September 21 to 29, 2012. The one-minute time-resolution and high mass resolution (up to $4000m{\Delta}m^{-1}$) data from the PTR-ToF-MS provided the basis for calculations of the concentrations of anthropogenic and biogenic volatile organic compounds (BVOCs) including oxygenated VOCs (OVOCs). The dominant BVOCs from the site are isoprene (0.23 ppb), dimethyl sulphide (DMS, 0.20 ppb), and monoterpenes (0.38 ppb). Toluene (0.45 ppb) and benzene (0.32 ppb) accounted for the majority of anthropogenic VOCs (AVOCs). OVOCs including acetone (3.98 ppb), acetaldehyde (2.67 ppb), acetic acid (1.68 ppb), and formic acid (2.24 ppb) were measured. The OVOCs comprise approximately 75% of total measured VOCs, suggesting the occurrence of strong oxidation processes and/or long-range transported at the site. A strong photochemical aging and oxidation of the atmospheric pollutants were also observed in aerosol measured by HR-ToF-AMS, whereby a high $f_{44}:f_{43}$ value is shown for organic aerosols (OAs); however, relatively low $f_{44}:f_{43}$ values were observed when high concentrations of BVOCs and AVOCs were available, providing evidence of the formation of SOA from VOC precursors at the site. Overall, the results of this study revealed several different SOA formation mechanisms, and new particle formation and particle growth events were identified using the powerful tools scanning mobility particle sizer (SMPS), PTR-ToF-MS, and HR-ToF-AMS.

• 상하수도학회지
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• 제18권6호
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• pp.731-741
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• 2004

The purpose of this study was to evaluate the potential of a gamma ray irradiation to decompose hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in an aqueous solution. The decomposition reaction of RDX by gamma ray irradiation was a first-order kinetic over the applied initial concentrations (10-40mg/L). The dose constant was strongly dependent on the initial concentration of the RDX. The removal of RDX was more efficient at pH below 3 and at pH above 11 than at neutral pH (pH 5-9). The required irradiation dose to remove 99% of the RDX (40mg/L) was 4, 8 and 1 kGy, at pH 2, 7 and 13, respectively. The dose constant was increased by two folds and over twelve folds at pH 2 and 13, respectively, when compared with that at pH 7. When an irradiation dose of 20 kGy was applied, the removal efficiencies of TOC were 80, 57 and 91% at pH 2, 7 and 13, respectively. Ammonia and nitrate were detected as the main nitrogen byproducts of RDX and formic acid was detected as an organic byproduct. The results showed that a gamma ray irradiation was an attractive method for the decomposition of RDX in an aqueous solution and it was found that a strong alkaline pH over 12 should be applied to the decomposition reaction of RDX.