• 대한환경공학회지
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• 제27권7호
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• pp.746-752
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• 2005

본 연구에서는 저임계 습식산화 조건에서 반응온도, 시간 및 압력 등 반응조건이 슬러지의 분해 및 유기산의 생성에 미치는 영향을 조사하였다. 또한, 저임계 습식산화의 분해경로 및 수정된 동력학적 모델을 제안하였으며, 다양한 조건에서 수행된 실험결과와 예측치를 비교, 검토하였다. 회분식 실험결과 반응온도는 산화반응보다는 열적가수분해 반응에 직접적으로 영향을 미치며, 반응온도와 시간이 증가할수록 슬러지의 분해효율과 유기산의 생성효율이 증가하는 것으로 나타났다. 반응온도 $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ 및 $240^{\circ}C$, 반응시간 10 min에서 SS 농도의 제거율이 52.6%, 68.3%, 72.6% 및 74.4%로 나타나 반응 초기에 유기성 고형물(총 고형물의 약 75%)의 대부분이 액상화가 진행된 것으로 판단된다. 반응온도 $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ 및 $240^{\circ}C$, 반응시간 40 min에서 제거 슬러지당 생성된 유기산은 각각 93.5 mg/g SS, 116.4 mg/g SS, 113.6 mg/g SS 및 123.8 mg/g SS이며, 아세트산 생성은 24.5 mg/g SS, 65.5 mg/g SS, 88.1 mg/g SS 및 121.5 mg/g SS로 나타나 반응온도가 증가할수록 유기산의 생성율도 증가하였으며, 분해되기 쉬운 유기산이 아세트산으로 전환되는 것으로 나타났다. 제안한 수정 동력학적 모델에서 반응온도가 증가함에 따라 반응속도상수 $k_1$(고형물의 액상화), $k_2$(중간산물의 유기산 생성), $k_3$(중간산물의 최종분해) 및 $k_4$(유기산의 최종 분해) 모두 증가하였다. 이는 반응온도의 증가에 따른 유기성 고형물질의 액상화와 유기산 생성율의 증가를 의미한다. 반응속도상수($k_1{\sim}k_4$)에 대한 활성화에너지를 산정한 결과, 각각 20.7 kJ/mol, 12.3 kJ/mol, 28.4 kJ/mol 및 54.4 kJ/mol로 나타나 열적가수분해 반응 보다는 산화반응이 율속단계인 것으로 판단된다.

• 폴리머
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• 제32권2호
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• pp.150-156
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• 2008

Two different polyacrylonitrile samples (PANs, triad tacticity fraction is 0.25 and 0.64) were synthesized and used to study the kinetics of cyclization. Polymers were treated at different temperatures between 250 to $300^{\circ}C$ under air atmosphere, and analyzed by X-ray diffractometer. The sharp and strong peak at $2{\theta}=16.5^{\circ}$ corresponds to a lateral repeat distance that is the (100) diffraction in hexagonal lattice, while the peak at $2{\theta}=25.5^{\circ}$ reflects the (101) diffraction. In comparing their areas of different heat treated samples, the cyclization of both PANs was identified as a first-order reaction. The rate constants of cyclization reaction at different temperatures and the active energy parameter were obtained. This results might provide an important effect on pre-oxidation of polyacrylonitrile fiber.

• Journal of Microbiology and Biotechnology
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• 제27권4호
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• pp.768-774
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• 2017

Horseradish peroxidase (HRP) catalyzes the oxidation of aromatic compounds by hydrogen peroxide via insoluble polymer formation, which can be precipitated from the wastewater. For HRP immobilization, poly(lactic-co-glycolic acid) (PLGA) fine carrier supports were produced by using the Nano Spray Dryer B-90. Immobilized HRP was used to remove the persistent 2,4-dichlorophenol from model wastewater. Both extracted (9-16 U/g) and purified HRP (11-25 U/g) retained their activity to a high extent after crosslinking to the PLGA particles. The immobilized enzyme activity was substantially higher in both the acidic and the alkaline pH regions compared with the free enzyme. Optimally, 98% of the 2,4-dichlorophenol could be eliminated using immobilized HRP due to catalytic removal and partly to adsorption on the carrier supports. Immobilized enzyme kinetics for 2,4-dichlorophenol elimination was studied for the first time, and it could be concluded that competitive product inhibition took place.

• 한국분무공학회지
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• 제18권1호
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• pp.21-26
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• 2013

Diesel low temperature combustion (LTC) is the concept where fuel is burned at a low temperature oxidation regime so that $NO_x$ and particulate matters (PM) can simultaneously be reduced. There are two ways to realize low temperature combustion in compression ignition engines. One is to supply a large amount of EGR gas combined with advanced fuel injection timing. The other is to use a moderate level of EGR with fuel injection at near TDC which is generally called Modulated kinetics (MK) method. In this study, the effects of fuel injection pressure on performance and emissions of a single cylinder engine were evaluated using the latter approach. The engine test results show that MK operations were successfully achieved over a range of with 950 to 1050 bar in injection pressure with 16% $O_2$ concentration, and $NO_x$ and PM were significantly suppressed at the same time. In addition, with an increase in fuel injection pressure, the levels of smoke, THC and CO were decreased while $NO_x$ emissions were increased. Moreover, as fuel injection timing retarded to TDC, more THC and CO emissions were generated, but smoke and $NO_x$ were decreased.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.37-44
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• 2013

Generally, a reduced chemical mechanism of n-heptane is used as chemical fuel of a 3-D diesel engine simulation because diesel fuel consists of hundreds of chemical components and various chemical classes so that it is very complex and large to use for the calculation. However, the importance of fuel in a 3-D simulation increases because detailed fuel characteristics are the key factor in the recent engine research such as homogeneous charged compression ignition engine. In this study, normal paraffin, iso paraffin and aromatics were selected to represent diesel characteristics and n-dodecane was used as a representative normal paraffin to describe the heavy molecular weight of diesel oil (C10~C20). Reduced kinetics of iso-octane and toluene which are representative species of iso paraffin and aromatics respectively were developed in the previous study. Some species were selected based on the sensitivity analysis and a mechanism was developed based on the general oxidation scheme. The ignition delay times, maximum pressure and temperature of the new reduced n-dodecane chemical mechanisms were well matched to the detailed mechanism data.

• 한국진공학회지
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• 제6권S1호
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• pp.96-109
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• 1997

In order to simulate the corrosion behavior of Zr-4 alloy in pressurized water reactors it was implanted (or bombarded) with 190ke V $Zr^+\; and \;Ar^+$ ions at liquid nitrogen temperature and room temperature respectively up to a dose of $5times10^{15} \sim 8\times10^{16} \textrm{ions/cm}^2$ The oxidation behavior and electrochemical vehavior were studied on implanted and unimplanted samples. The oxidation kinetics of the experimental samples were measured in pure oxygen at 923K and 133.3Pa. The corrosion parameters were measured by anodic polarization methods using a princeton Applied Research Model 350 corrosion measurement system. Auger Electron Spectroscopy (AES) and X-ray Photoelectric Spectroscopy (XPS) were employed to investigate the distribution and the ion valence of oxygen and zirconium ions inside the oxide films before and after implantation. it was found tat: 1) the $Zr^+$ ion implantation (or bombardment) enhanced the oxidation of Zircaloy-4 and resulted in that the oxidation weight gain of the samples at a dose of $8times10^{16}\textrm{ions/cm}^2$ was 4 times greater than that of the unimplantation ones;2) the valence of zirconium ion in the oxide films was classified as $Zr^0,Zr^+,Zr^{2+},Zr^{3+}\; and \;Zr^{4+}$ and the higher vlence of zirconium ion increased after the bombardment ; 3) the anodic passivation current density is about 2 ~ 3 times that of the unimplanted samples; 4) the implantation damage function of the effect of ion implantation on corrosion resistance of Zr-4 alloy was established.

• Environmental Engineering Research
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• 제24권3호
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• pp.474-483
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• 2019

In this study, iron (Fe) impregnated granular activated carbon (Fe-GAC) has been synthesized and characterized for various properties. Comparative studies have been performed for use of Fe-GAC as an adsorbent as well as a catalyst during catalytic oxidation of hydroquinone (HQ). In the batch adsorption study, effect of process parameter like initial HQ concentration ($C_o=25-1,000mg/L$), pH (2-10), contact time (t: 0-24 h), temperature (T: $15-45^{\circ}C$) and adsorbent dose (w: 5-50 g/L) have been studied. Maximum HQ adsorption efficiency of 75% was obtained at optimum parametric condition of: pH = 4, w = 40 g/L and t = 14 h. Pseudo-second order model best-fitted the HQ adsorption kinetics whereas Langmuir model best-represented the isothermal equilibrium behavior. During oxidation studies, effect of various process parameters like initial HQ concentration ($C_o:20-100mg/L$), pH (4-8), oxidant dose ($C_{H2O2}:0.4-1.6mL/L$) and catalyst dose (m: 0.5-1.5 g/L) have been optimized using Taguchi experimental design matrix. Maximum HQ removal efficiency of 83.56% was obtained at optimum condition of $C_o=100mg/L$, pH = 6, $C_{H2O2}=0.4mL/L,$ and m = 1 g/L. Overall use of Fe-GAC during catalytic oxidation seems to be a better as compared to its use an adsorbent for treatment of HQ bearing wastewater.

• 방사성폐기물학회지
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• 제2권4호
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• pp.239-244
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• 2004

사용후핵연료 금속전환체의 저장 안정성을 높이기 위해 금속전환체의 주성분인 금속우라늄과 산화 안정화물질로 알려져 있는 Nb을 첨가하여 모의 금속전환체 합금을 제작하였다. 모의 금속전환체 합금을 $200{\sim}300^{\circ}C$ 온도구간에서 순수 산소분위기로 산화시험을 수행하고 무게증가(wt%)를 열중량 분석기(TGA)로 측정하였다. 산화 실험결과 U-Nb 모의 금속전환체는 순수 금속우라늄에 비하여 상당한 산화 저항성을 가졌다. U-Nb 합금의 경우 Nb의 함량 1, 2, 3, 4 wt%에 따라 각각 온도가 $200^{\circ}C$일 경우에는 1.61, 7.78, 11.76, 20.14배 , $250^{\circ}C$에서 1.45, 5.98, 10.08, 11.15배, $300^{\circ}C$에서 1.33, 4.82, 8.87, 6.84배 순수 금속우라늄에 비해 산화저항성이 향상되는 것으로 나타났다. 또한 U-1~4 wt%Nb 합금에 대한 활성화에너지는 17.13~21.92 kcal/mol 로 나타났다.

• 대한환경공학회지
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• 제31권10호
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• pp.927-932
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• 2009

난분해성 및 독성 폐수 처리는 고급산화 기술과 생물학적 처리가 친화결합(intimate coupling) 을 이룰 때 최적의 효과를 거둘 수 있다. 본 연구에서는 광촉매 산화와 생물학적 처리를 친화결합하도록 고안된 다공성 $TiO_2$ 코팅 담체를 제조하여 광촉매 반응에 관한 동력학 연구를 수행하였다. 저온 sol-gel 코팅법으로 제조된 PVA 재질의 다공성 $TiO_2$ 담체는 UV 조사하에서 methylene blue (MB)를 효율적으로 분해하였다. 시험 농도(최대 100 ${\mu}M$)에서 MB의 흡착속도는 1차반응 (first-order reaction)의 성질을 보였으며, 흡착과 산화를 포함한 총반응속도는 유사 Langmuir 모델로 예측 가능하였다. 이러한 원인은 담체 표면에 MB가 흡착됨에 따라 UV 조사에 의하여 광촉매 반응이 일어날 표면이 줄어들었기 때문인 것으로 판단된다. 다공성 $TiO_2$ 담체의 단위 $TiO_2$ 량당 최대 MB 제거속도는 슬러리 $TiO_2$ 반응기에서 얻은 MB 제거속도보다 4배 더 빨랐다. 본 연구로 인하여 저온 sol-gel 코팅법으로 제조한 PVA 재질 다공성 $TiO_2$ 담체가 성공적인 광분해 반응을 나타내는 것이 확인되었으며, 동 담체에 대한 광촉매 반응의 동력학적 성질이 구명되어, 향후 생물처리를 친화결합 시킬 수 있는 연구 바탕을 확보하였다.

• 대한화학회지
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• 제60권3호
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• pp.169-176
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• 2016

Borate 완충용액에서 Al의 부식과 부동화에 관하여 변전위법, 대 시간 전류법 그리고 다중 주파수 전기화학적 임피던스 측정법으로 조사하였다. 공기 또는 산소의 영향은 환원과정에 영향을 주었지만 산화반응에는 영향을 미치지 못 하는 것으로 보인다. 부동화 영역에서 생성되는 피막의 전기적 성질은 Mott-Schottky 식이 적용되는 n-type 반도체 성질을 보였다. 낮은 전극전위에서 생성되는 Al의 산화피막은 Al(OH)₃로 충분한 부동화 효과를 보이지 못하나, 전극전위가 증가하면서 Al₂O₃로 변하였다. Al₂O₃ 피막은 “전기장에 의한-이온의 이동” 과정에 의하여 성장하는 것으로 보인다.