• Title/Summary/Keyword: Pre-oxidation

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Study on the Sr-ferrite sintered magnets using mill scale (밀 스케일을 활용한 Sr-페라이트 소결자석의 연구)

  • 조태식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07a
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    • pp.82-85
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    • 2002
  • High-quality Sr-ferrite sintered magnets have been studied by using mill scale added SrCO$_3$ and oxidents before oxidation process. The pre-added SrCO$_3$ powders were improved the degree of oxidation and crush of mill scale and the magnetic properties of Sr-ferrite sintered magnets. The small added NaNO$_3$ oxidant was also highly improved the degree of oxidation and crush of mill scale and the magnetic properties of Sr-ferrite sintered magnets; 3805 G of remanent flux density, 3240 Oe of intrinsic coercivity, and 3.45 MGOe of maximum energy product.

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Decomposition Characteristics of Dissolved Organic Compounds in the Landfill Leachate by Ozone Oxidation (오존산화에 의한 매립지 침출수내 용존성 유기화합물의 분해 특성)

  • 정승현;이헌모;정병곤
    • Journal of environmental and Sanitary engineering
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    • v.18 no.1
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    • pp.23-29
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    • 2003
  • The effect of ozone oxidation on bio-degradability of leachate was studied. Ozone oxidation process was used as pre-treatment process to enhance performance of biological process in treating landfill leachate. Optimum ozone injection rate and contact time in this experiment was $160{\;}mg{\;}O_/{\ell}{\cdot}hr$ and 45 minutes, respectively. Bio-degradability was enhanced 5.08% by ozone oxidation. The ratio of ozone demand/DOC concentration was $0.049~0.091{\;}mg{\;}O_3/mg{\;}DOC$. The increase of bio-degradability depending on ozone injection rate(D) and contact time(T) can be expressed as follows ; The rate of bio-degradation of DOC was increased proportionally with the increase of ozone injection rate and contact time irrespective of landfill site age. The increase of bio-degradability by ozone addition was not satisfactory. It is hard to expect significant increase in bio-degradability by ozone treatment only. Thus, it is evaluated that ozone oxidation can not increase biodegradability significantly in concentrated wastewater composed of complex organic compound such as leachate.

Effect of Ozone Oxidation on Biodegradability of Dissolved Organic Compounds in the Landfill Leachate (오존산화가 매립지 침출수내 용존성 유기화합물의 생분해도에 미치는 영향)

  • Jeong, Seung-Hyun;Jeong, Byung-Gon
    • Journal of Korean Society on Water Environment
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    • v.21 no.1
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    • pp.1-6
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    • 2005
  • The effect of ozone oxidation on biodegradability of leachate was studied. Ozone oxidation process was used as pre-treatment process to enhance performance of biological process in treating landfill leachate. Optimum ozone dosing rate and contact time in this experiment was $160mg\;O_3/L$ hr and 45 minutes, respectively. Biodegradability was enhanced 5.08% by ozone oxidation. The ratio of ozone demand/DOC concentration was $0.049{\sim}0.091mg\;O_3/mg$ DOC. The increase of biodegradability depending on ozone dosing rate(D) and contact time(T) can be expressed as follows ; ${\Delta}E=0.00479{\cdot}D^{0.773}{\cdot}T^{0.800}$ The biodegradation rate of DOC was increased proportionally with the increase of ozone dosing rate and contact time irrespective of landfill site age. The increase of biodegradability by ozone addition was not satisfactory. It is hard to expect significant increase in biodegradability by ozone treatment only. Thus, it is evaluated that ozone oxidation can not increase biodegradability significantly in concentrated wastewater composed of complex organic compound such as leachate.

The Effects of Smoking Cessation and Antioxidant Vitamins on Oxidative Stress

  • Ha, Aewha
    • Nutritional Sciences
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    • v.9 no.4
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    • pp.288-294
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    • 2006
  • In this study, the effects of smoking cessation and relative antioxidant activities on the oxidative stress were determined by using in vitro method. Thirty healthy smokers who were free of any disease and smoked more than 1 pack per day for the past 10 years participated in this study. For smoking cessation, smokers were asked to wear nicotine patch (21mg nicotine/ patch) everyday for 30 days and then to replace at the same time of the day. Smoking cessation program in conjunction with nicotine patch replacement was also conducted every week, one hour/each session, for 4 weeks. Canthaxanthin, $\beta-carotene$, and $\alpha-tocopherol$ were added into red blood cells at pre and post smoking cessation. As indicators of oxidative stress, hemoglobin degradation, lipid peroxidation, and percent hemolysis were determined at both pre and post smoking cessation. After 30 days of smoking cessation, the subjects gained an average of 5 pounds, varying 2 to 8 pounds, by suggesting that behavioral problems rather than nicotine itself are more important for gaining weight in ex-smokers. The total hemoglobin concentrations in blood were similar in pre and post smoking cessation, but smoking cessation resulted in a decrease in the percentage of methemoglobin from 0.96% to 0.85% Smoking cessation also caused to decease malondialdehyde (MDA) values ($26.7{\pm}7.8$ vs. $23.6{\pm}4.5$ (without oxidation), $179.3{\pm}21$ vs. $161.2{\pm}28$ nmol/ml (with oxidation) (p<0.05)), not percent hemolysis. Various antioxidants with smoking cessation significantly decreased MDA values(p<0.05), in contrast to marginal decrease of MDA in smoking cessation only. Three antioxidants used in this stu study were similarly effective in inhibiting MDA production, but relative effectiveness of canthaxanthin or $\alpha-tocopherol$ was greater than that of $\beta-carotene$ (p<0.05), in case of oxidation induced. The percent hemolysis was greatly decreased when antioxidants were added into the blood of ex-smokers (p<0.05) but no statistical significance in relative effectiveness of antioxidants was observed.

Carbon Deposition on Nickel Catalyst for Pre-reforming of Propane (니켈 촉매를 이용한 프로판 예개질 반응의 탄소침적에 대한 연구)

  • Kim, Sun-Young;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.05a
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    • pp.487-490
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    • 2008
  • Temperature programmed oxidation (TPO) is used to characterize coke species deposited on commercial nickel catalyst, C11-PR during propane pre-reforming. Propane pre-reforming performed under various condition, S/C from 1.5 to 2.5 and temperature from $350^{\circ}C$ to $450^{\circ}C$. There are three kinds of coke species detected by TPO: (i) reactive coke, (ii) coke deposited on metal site and (iii) coke deposited on acid support. Coke deposited on metal and support are minimized although reactive coke is generated at temperature of $400^{\circ}C$ and S/C of 2.0. Reactive coke is expected to remove easily below temperature of $200^{\circ}C$. Therefore, optimized pre-reforming condition for propane is $400^{\circ}C$ and S/C of 2.0.

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Char Oxidation Characteristics of High Ash Coal in Drop Tube Furnace (고회분탄의 촤 산화 반응 특성 연구)

  • An, Ke-Ju;Lee, Byoung-Hwa;Kim, Sang-In;Kim, Man-Cheol;Kim, Seung-Mo;Jeon, Chung-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.4
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    • pp.405-413
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    • 2013
  • The char oxidation characteristics of high ash coal were experimentally investigated at several temperatures (from 900 to $1300^{\circ}C$) for 4 types of coals (Gunvor, Glencore, Noble, and ECM) under atmospheric pressure in a drop tube furnace (DTF). The char reaction rate was calculated from the exhaust gas concentrations (CO and $CO_2$) using FT-IR, and the particle temperature was measured using the two-color method. In addition, the activation energy and pre-exponential factor for high ash coal char were calculated based on the Arrhenius equation. The results show that as the ash content increases, the particle temperature and area reactivity decreases. This is because in high ash coal, the large heat capacity of the ash, ash vaporization, and relatively low fixed carbon content of ash suppress combustibility during char oxidation. As a result, the higher ash content of coal leads to high activation energy.

Recent Progress of Automotive Galvanized Steels in Korea

  • Lee, Suk-Kyu;Kim, Jong-Sang;Choo, Wung-Yong
    • Corrosion Science and Technology
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    • v.9 no.6
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    • pp.254-258
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    • 2010
  • Due to the global warming and economic crisis, automakers are currently focusing on the development of high fuel-efficiency vehicles. To accord with these requirements, steelmakers have been trying to develop advanced high-strength steels with improved automotive-related properties. In addition, galvanizing technologies have been developed to improve coating properties for AHSS (Advanced High Strength Steel) such as pre-oxidation and pre-coating, as well as roll dent prevention. In this paper, newly developed products and technologies for automotive galvanized steel sheet are reviewed.

Surface Modification of Cellulose Nanofibrils by Carboxymethylation and TEMPO-Mediated Oxidation (카르복시메틸화 및 TEMPO 촉매 산화 처리에 의한 셀룰로오스 나노피브릴의 표면 개질)

  • Sim, Kyujeong;Youn, Hye Jung;Jo, Yeonhee
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.47 no.2
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    • pp.42-52
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    • 2015
  • In this study, cellulose nanofibrils (CNF) were modified through carboxymethylation or TEMPO-mediated oxidation and their effects on ionicity and characteristics of sheet, film, and foam were investigated. Carboxymethylation was carried out on pulp fibers as a pre-treatment before preparation of CNF. The gel-like and translucent CNF hydrogel was obtained by grinding of carboxymethylated cellulose fibers. Carboxymethylated CNF film and freeze dried sheet showed higher transparency than that of untreated CNF. The CNF sheet with high strength and the CNF foam without large ice crystals were obtained by using the carboxymethylated CNF. TEMPO-mediated oxidation was carried out as a post-treatment of CNF. The zeta potential and charge demand of TEMPO-oxidized CNF were increased with an increase in oxidation time and addition amount of NaClO. The density of sheet made of TEMPO oxidized CNF was increased with the amount of oxidizing agent. The TEMPO oxidized cellulose nanofiber (TOCN) which was obtained from supernatant after centrifugation could be converted to transparent film.

Electro-Oxidation in Combination with Biological Processes for Removal of Persistent Pollutants in Wastewater: A Review

  • Navarro-Franco, Javier A.;Garzon-Zuniga, Marco A.;Drogui, Patrick;Buelna, Gerardo;Gortares-Moroyoqui, Pablo;Barragan-Huerta, Blanca E.;Vigueras-Cortes, Juan M.
    • Journal of Electrochemical Science and Technology
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    • v.13 no.1
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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.