• 한국응용과학기술학회지
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• 제34권2호
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• pp.367-375
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• 2017

본 연구에서는 배가스 내 존재하는 오염물질인 NO의 처리효율을 증대시키기 위하여 NO 산화공정을 연구하였으며, 강력한 산화력의 건식산화제를 제조하는 방법으로 $H_2O_2$ 촉매분해가 도입되었다. $H_2O_2$ 분해공정 상에서 적용 가능한 $K-Mn/Fe_2O_3$ 불균일계 촉매가 제조되었으며, 이들이 가지는 물리화학적 특성이 $H_2O_2$ 분해반응에 미치는 영향이 조사되었다. 제조된 건식산화제는 NO가 포함된 모사 배가스를 처리하기 위한 NO 산화공정에 적용되었으며, 다양한 모사 배가스의 유량(5, 10, 20 L/min)에서 약 100% 가까운 NO 전환율을 확인 하였다.

• 한국환경과학회지
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• 제14권10호
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• pp.919-928
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• 2005

This study introduces the development of new supercritical water oxidation(SCW)(multiple step oxidation) to destruct recalcitrant organic substances totally and safely by using sodium nitrate as an oxidant. This method has solved the problems of conventional SCW, such as precipitation of salt due to lowered permittivity, pressure increase following rapid rise of reaction temperature, and corrosion of reactor due to the generation of strong acid. Destruction condition and rate in the supercritical water were examined using Polyvinyl Chloride(PVC) and ion exchange resins as organic substances. The experiment was carried out at $450^{\circ}C$ for 30min, which is relatively lower than the temperature for supercritical water oxidation $(600-650^{\circ}C)$. The decomposition rates of various incombustible organic substances were very high [PVC$(87.5\%)$, Anion exchange resin$(98.6\%)$, Cationexchange resin$(98.0\%)$]. It was observed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium (salt formation). However, relatively large amount of sodium nitrate (4 equivalent) was required to raise the decomposition ratio. For complete oxidation of PCB was intended, the amount of oxidizer was an important parameter.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권2호
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• pp.17-25
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• 2017

The efficiency and mechanism of electrochemical phenol oxidation using persulfate (PS) and nanosized zero-valent iron (NZVI) were investigated. The pseudo-first-order rate constant for phenol removal by the electrochemical/PS/NZVI ($1mA^*cm^{-2}/12$ mM/6 mM) process was $0.81h^{-1}$, which was higher than those of the electrochemical/PS and PS/NZVI processes. The electrochemical/PS/NZVI system removed 1.5 mM phenol while consuming 6.6 mM PS, giving the highest stoichiometric efficiency (0.23) among the tested systems. The enhanced phenol removal rates and efficiencies observed for the electrochemical/PS/NZVI process were attributed to the interactions involving the three components, in which the electric current stimulated PS activation, NZVI depassivation, phenol oxidation, and PS regeneration by anodic or cathodic reactions. The electrochemical/PS/NZVI process effectively removed phenol oxidation products such as hydroquinone and 1,4-benzoquinone. Since the electric current enhances the reactivities of PS and NZVI, process performance can be optimized by effectively manipulating the current.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2005년도 봄 학술발표회지 제14권(제1호)
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• pp.267-271
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• 2005

This experiment was carried out at 450"C, which is relatively lower than the temperature for supercritical water oxidation (600-650$^{\circ}C$). In this experiment, the decomposition rates of various incombustible organic substances were very high. In addition, it was confirmed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium(salt formation).However, to raise the decomposition rate, relatively large amount of sodium nitrate(3-4 times the equivalent weight) was required. When complete oxidation is intended as in the case with PCB, the amount of oxidizer and decomposition cost is important. But when vaporization reduction is required as in the case with nuclear wastes, the amount of radioactive wastes increases instead. But as can be seen in the result of XRD measurement, unreacted sodium nitrate remained unchanged. If oxidation reaction of organic substance simply depends on collision frequency, unreacted sodium nitrate can be recovered and reused, then oxidation equivalent weight would be sufficient. In the gas generated, toxic gas was not found. As the supercritical water medium has high reactivity, it is difficult to generate relatively low energy level SO$_{X}$, and NO$_{X}$.

• Carbon letters
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• 제4권4호
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• pp.185-191
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• 2003

Two types of carbon fiber based high modulus- and isotropic-pitch were exposed to isothermal oxidation in air and $CO_2$ gas and the weight change was measured by TGA apparatus. The kinetic equation was introduced $f=1-{\exp}(-at^b)$ and the constant b was obtained in the range of 1.02~1.68 for the isotropic fiber and obtained 0.91~1.93 for the high modulus fiber respectively. In considering the effect of the atmosphere for isothermal oxidation, the value of the constant b obtained in the carbon dioxide was higher than that obtained in the air. Therefore, it was found that the pitch based carbon fiber shows sigmoidal characteristic when it is oxidized in the carbon dioxide. In addition, it was also found that $k_f = 0.5$, which was reaction constant at f = 0.5, was a very useful parameter for evaluation of the oxidation reactivity of pitch based carbon fibers. According to the consideration, it is suggested that the conversion-time curves of the pitch based carbon fibers are correlated by normalized equation $f=1-{\exp}(-A{\tau}^B)$, where ${\tau}=t/t_f= 0.5$.

• Corrosion Science and Technology
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• 제7권3호
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• pp.145-151
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• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
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• pp.96-97
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• 2011

The T23 steel, whose composition was Fe-2.3%Cr-1.6%W, was arc-melted, and oxidized between $600^{\circ}C$ and $900^{\circ}C$ in air for up to 7 months. The amount of precipitates in the arc-melted microstructure was as large as 11.4 vol.%. The precipitates increased the oxidation rate of the arc-melted T23 steel. Owing to the low amount of Cr in the T23 steel, breakaway oxidation occurred after a few hours during oxidation above $700^{\circ}C$ in both arc-melted and as-received T23 steels. The scales that formed on arc-melted and as-received T23 steels were similar to each other. They consisted primarily of the outer $Fe_2O_3$ layer and the inner ($Fe_2O_3$, $FeCr_2O_4$)-mixed layer. The precipitates increased the microhardness and the oxidation rates.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.1-18
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• 2022

Persistent organic pollutants (POPs) and emerging pollutants (EP) are characterized by their difficulty to be removed through biological oxidation processes (BOPs); they persist in the environment and could have adverse effects on the aquatic ecosystem and human health. The electro-oxidation (EO) process has been successfully used as an alternative technique to oxidize many kinds of the aforementioned pollutants in wastewater. However, the EO process has been criticized for its high energy consumption cost and its potential generation of by-products. In order to decrease these drawbacks, its combination with biological oxidation processes has been reported as a solution to reduce costs and to reach high rates of recalcitrant pollutants removal from wastewaters. Thus, the location of EO in the treatment line is an important decision to make, since this decision affects the formation of by-products and biodegradability enhancement. This paper reviews the advantages and disadvantages of EO as a pre and post-treatment in combination with BOPs. A perspective of the EO scale-up is also presented, where hydrodynamics and the relationship of A/V (area of the electrode/working volume of the electrochemical cell) experiments are examined and discussed.

• 한국결정성장학회지
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• 제6권2호
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• pp.185-193
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• 1996

(100) Si wafer를 $2.5^{\circ},\;5^{\circ}$ 기울인 뒤, dry $O_{2}$ 분위기에서 산화시킴으로써, 시편들 간의 산화 거동 및 산화에 의한 적층 결함 특성의 차이를 알아보았다. 시편을 $900~1200^{\circ}C$에서 산화시키고 ellipsometer로 두께를 측정한 결과 저탈각 (100) Si이 (100) Si보다 산화 속도가 빨랐으며, $5^{\circ}$ off면이 $2.5^{\circ}$ off면보다 더 빨랐다. 결정방향에 따른 산화속도 차이는 산화 온도가 높아질수록 줄어들었다. 각 시편의 속도 상수에 대한 활성화 에너지는 포물 성장 속도 상수의 경우 (100) Si, $2.5^{\circ}$ off (100) Si, $5^{\circ}$ off Si이 각각 27.3, 25.9, 27.6 kcal/mol이였고, 선형 성장 속도 상수는 58.6, 56.6, 57.4 kcal/mol이였다. 또한, 두 시편에 대해 산화막을 선택 식각하 고 광학 현미경으로 관찰하여, (100) Si에 비해 $5^{\circ}$ off된 면의 산화에 의한 적층 결함 밀도가 훨씬 낮음을 확인하였고, 적층 결함 간의 각도가 달라짐을 확인하였다.

• BMB Reports
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• 제29권1호
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• pp.81-87
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• 1996

The relationship of S-thiolation and oxidation of glycogen phosphorylase b and peroxidation of phosphatidyl choline liposome by xanthine oxidase (XOD), 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH), and 2,2'-azobis(dimethylvaleronitrile) (AMVN)-generated free radicals was investigated, Glycogen phosphorylase b was S-thiolated in the presence of glutathione and oxidized in the absence of it by XOD, AAPH and AMVN. In XOD-initiated reaction, the rates of S-thiolation and oxidation of phosphorylase were very similar and addition of liposome to the reaction mixture showed little inhibition of the modifications. In AAPH-initiated reaction, the rate of oxidation was higher than that of S-thiolation and addition of liposome increased oxidation of the protein but had no effect on S-thiolation. In AMVN-initiated reaction, S-thiolation was higher than oxidation and addition of liposome increased S-thiolation remarkably but showed no effect on oxidation. The effect of liposome on modifications of protein in AAPH and AMVN reaction seemed to be caused by certain reactive degradation products or intermediates of liposome by free radical attack. Peroxidation of liposome was not observed in XOD-initiated reaction. Liposome was gradually peroxidized by AAPH reaction. The peroxidation was inhibited by addition of GSH and phosphorylase. Peroxidation of liposome by AMVN was extreamly fast, and was not affected by GSH and phosphorylase.