• Bulletin of the Korean Chemical Society
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• 제8권5호
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• pp.389-393
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• 1987

The oxidation of carbon monoxide by gaseous oxygen on 0.53, 1.02, and 1.51 mol $\%$CoO-doped $-Fe_2O_3$ catalysts has been investigated in the temperature range from 340 to 480$^{\circ}C$ under various CO and $O_2$ partial pressures. The oxidation rates have been correlated with 1.5-order kinetics; the 0.5-order with respect to $O_2$ and the first-order with respect to CO. In the above temperature range, the activation energy is 0.34 $\pm$ 0.01 eV${\cdot}$$mol^{-1}$. The electrical conductivity of 0.53, 1.02, and 1.51 mol %CoO-doped $\alpha$-$Fe_2O_3$ has been measured at 350$^{\circ}C$ under various $P_{CO}and $P_{O_2}$. From the conductivity data it was found that $O_2$ was adsorbed on Vo formed by doping with CoO, while CO appeared essentially to be chemisorbed on the lattice oxygen of the catalyst surface. The proposed oxidation mechanism and the dominant defect were supported by the agreement between the kinetic data and conductivities.

• Applied Biological Chemistry
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• 제37권5호
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• pp.414-420
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• 1994

망간 산화물 birnessite, pyrolusite, hausmannite의 표면에서 일어나는 3가 크롬의 산화현상을 조사하였다. 이들은 zero point of charge, 표면적, 그리고 결정도 등에서 차이가 많은데, 크롬 산화현상은 모두 1차 반응이었으며 반응용액의 pH 및 최초 3가 크롬농도가 반응에 큰 영향을 미쳤다. 일반적으로 hausmannite에 의한 산화가 가장 빨랐으며 pyrolusite에 의한 산화는 상대적으로 매우 느렸다. 용액 pH와 최초 3가 크롬농도의 상호 작용이 전체 반응속도를 조절하는 것 같으며 pH가 높고 3가 크롬농도가 높을 경우 망간산화물 표면에 3가 크롬 침전되거나 complex를 형성할 수 있을 것이다. Birnessite와 hausmannite에서는 $pH\;3.0{\sim}5.0$ 범위에서 pH가 낮을수록 산화력이 높았으나 pyrolusite의 경우에는 pH가 높을수록 산화력이 증가하였다. 반응속도는 온도에 또한 민감했다. pH 3.0에서의 산화반응의 activation energies는 일반적으로 diffusion에 필요한 activation energy보다 크게 나타났으나 반응속도를 결정하는 단계가 무엇인지는 확실하지 않다.

• Advances in environmental research
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• 제3권1호
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• pp.29-43
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• 2014

Pharmaceutical wastewater effluents are well known for their difficult elimination by traditional biotreatment methods and their important contribution to environmental pollution due to its fluctuating and recalcitrant nature. OTC is one of the nonbiodegradable antibiotics that makes antibiotic-resistant, so it can make be high risk for environment. NZVI can be a good choice for removal of OTC in aqueous solution. Response surface methodology (RSM) was used to optimize the amounts of NZVI and OTC to be used at pH 3 and under 200 W, UV-A irradiation. The responses were removal percent of absorption at 290 and 348 nm, TOC and COD of OTC. In the optimum condition, Linear model was performed 155 ppm of OTC were removed by 1000 ppm NZVI after 6.5 hours and the removal efficiency of absorption at 290 and 348 nm, TOC and COD were 87, 95, 85 and 89 percent, respectively. In the similar process, there is no organic compound after 14 hours. The parameters ORP, DO and pH were investigated for 6:30 hours to study the type of NZVI reaction in process. In the beginning of reaction, oxidation was the dominant reaction after 3 hours, photocatalytic reaction was remarkable. The mechanism of OTC degradation is proposed by HPLC/ESI-MS and four by products were found. Also the rate constants (first order kinetic chain reaction model) were 0.0099, 0.0021, 0.0010, 0.0049 and $0.0074min^{-1}$, respectively.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
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• pp.145-148
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• 2003

The batch experiments showed that 0.515mM 4-chlorophenol and its oxidation intermediates could be totally decomposed within 60 minutes by 1g/L steelers' dust and 0.485mM hydrogen peroxide at pH 2.7. The rate constants in the simplified kinetic model proposed in this study were estimated by fitting to the experimental data obtained in $H_2O$$_2$/steelers' dust system. Using the estimated kinetic rate constants, the simulation of 4-chlorophenol, ferrous iron, hydrogen peroxide, and hydroxyl radical concentration was performed. The predicted concentrations of 4-chlorophenol and hydrogen peroxide corresponded to the actual concentrations.

• Bulletin of the Korean Chemical Society
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• 제22권8호
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• pp.850-856
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• 2001

This study investigates the ozonation kinetics of 2-chlorophenol in wastewater under acidic condition. Intermediates and by-products generated during the process were rigorously identified and quantified. The major by-products are four carboxylic acids: tartaric acid, oxalic acid, maleic acid, and hydroxymalonic acid. The generation of these organic acids is in agreement with theoretical predictions. But hydroxylated compounds are more favorable to produce than their corresponding non-hydroxylated ones. Based on the information concerning the generation of organic acids and other aromatic intermediates, the complete reaction pathways toward mineralization can be proposed and mathematically modeled. The fitted second-order rate constants are in the same order of magnitude with the results from other studies. Using these oxidation pathways and the corresponding kinetic model, by-products generated in ozonation process can be predicted. This can help in optimizing the design and operation of any subsequent treatment processes.

• 한국식품영양과학회지
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• 제32권1호
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• pp.131-136
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• 2003

천연 항산화제인 tocopherol과 rosemary, tea polyphenol 을 아몬드 크래커에 첨가하여 $25^{\circ}C$와 35$^{\circ}C$에서 70일 동안 저장하면서 저장기간에 따른 항산화 효과를 살펴보았다 과산화물가를 측정하여 품질평가를 한 결과 $25^{\circ}C$에서는 rosemary 가 가장 우수한 항산화력을 보여주었고, 35$^{\circ}C$에서는 tea polyphenol이 우수하였다. 저장하는 동안 아몬드 크래커의 관능 검사에서는 rosemary와 tea polyphenol이 냄새와 맛에 좋은 영향을 주었고, $25^{\circ}C$에서 항산화제를 첨가하지 않은 blank 와 tocopherol은 42일, rosemary와 tea polyphenol은 56일이 지난 후에 제품으로서 품질을 잃는 것으로 나타났다. 35$^{\circ}C$에서는 $25^{\circ}C$에 비하여 모든 기호도 면에서 저하가 빠르게 일어났고, rosemary와 tea polyphenol이 blank와 tocopherol간의 차이가 유의 적으로 크게 나타났다. 천연 항산화제의 첨가에 따른 산화정도를 저장기간 동안 과산화물가의 변화를 이용하여 반응속도식를 구하였을 때, $25^{\circ}C$에서는 1차 반응식으로 나타났고, 35$^{\circ}C$에서는 0차 반응식이 결정되었다. 이때 반응속도 상수는 $25^{\circ}C$에서 rosemary가 -0.0299, 35$^{\circ}C$에서 tea polyphenol이 -.4038로 가장 낮은 수치를 보여주었다. 그러나 아몬드 크래커를 위한 항산화제 선택에 있어서는 저장온도에 따라 각각의 다른 천연항산화제가 영향을 주는 만큼 rosemary와 tea polypheno1을 함께 첨가하여 그 synergy 효과를 살피는 연구가 이루어져야 할 것이다.

• 대한기계학회논문집B
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• 제34권12호
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• pp.1101-1109
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• 2010

본 연구에서는 촤 연소 시에 분위기 가스 변화에 따른 연소 반응 변화를 수직 관형 연소로를 이용하여 실험적으로 측정해 보았다. 실험 조건으로 아역청탄인 Adaro탄과 역청탄인 Coal valley탄을 사용하였고, 두 탄을 $O_2/CO_2$조건과 $O_2/N_2$조건에서 온도를 900, 1100, $1300^{\circ}C$, 산소 분압을 12, 21, 30%로 변화를 주어 촤 반응성 실험을 수행하였다. 순산소 조건과 일반 대기 조건을 비교하였을 경우 순산소 조건일 때 입자온도와 총괄 반응량이 낮게 나타나는 경향을 보였지만, 입자 표면에서의 반응률을 계산한 결과, 분위기 가스의 영향과 상관없이 거의 동일한 경향을 가지는 것으로 나타났다. 또한 두 조건에서의 촤 연소 반응을 위한 반응 속도 상수 및 활성화 에너지 역시 분위기 가스의 영향과 상관없이 유사한 값을 가지는 것으로 확인하였다. 전반적으로 Adaro탄이 Coal valley탄보다 입자 온도와 총괄 반응량이 높게 나타났다.

• 대한화학회지
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• 제24권3호
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• pp.183-192
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• 1980

$SnO_2$, Sb-doped $SnO_2$>, 그리고 백금촉매하에서 일산화탄소의 산화반응을 연구하였다. $SnO_2$ 및 Sb-doped $SnO_2$ 촉매하에서 산화반응은 CO 및 $O_2$에 대해서 각각 1차, 백금 촉매하에서는 1/2차 반응에 따랐다. $SnO_2$에 소량의 Sb첨가(dopant composition : 0.05∼0.1mole%)는 반응속도를 증가시키고 그 이상의 첨가는 오히려 반응속도를 감소시켰다. 백금 촉매하의 산화반응에서는 일산화탄소의 농도가 증가함에 따라 반응속도가 오히려 감소하는 억제효과를 보여주었다. 각 촉매하에서 산화반응의 활성화에너지는 Sb-dopoped $SnO_2$ 촉매 (dopant compisito : 0.05 mole%)에서 5.7 kcal, 백금 촉매에서 6.4 kcal이었다. 실험적으로 얻은 반응차수와 doping 효과로부터 가능한 반응메카니즘을 제안하였다.

• 대한금속재료학회지
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• 제46권7호
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• pp.427-436
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• 2008

The effect of dewpoints on annealing behavior and coating characteristics such as wettability and galvannealing kinetics was studied by annealing 0.3wt%Si - 0.1~0.4wt% Mn added interstitial-free high strength steels(IF-HSS). The 0.3wt%Si-0.1wt%Mn steel exhibited good wettability with molten zinc and galvannealing kinetics after annealing when the dewpoint of $H_2-N_2$ mixed gas was above $-20^{\circ}C$. It is shown that the wettability and galvannealing kinetics are directly related to the coverage of the external(surface) oxide formed by selective oxidation during annealing. At $N_2-15%H_2$ annealing atmosphere, the increase of dewpoint results in a gradual transition from external to internal selective oxidation. The decrease of external oxidation of alloying elements with a concurrent increase of their subsurface enrichment in the substrate, showing a larger surface area that was free of oxide particles, contributed to the improved wettability and galvannealing kinetics. On the other hand, the corresponding wettability and galvannealing kinetics were deteriorated with the dewpoints below $-20^{\circ}C$. The continuous oxide layer of network and/or film type was formed on the steel surface, leading to the poor wettability and galvannealing kinetics. It causes a high contact angle between annealed surface and molten zinc and plays an interrupting role in interdiffusion of Zn and Fe during galvannealing process.

• Journal of Electrochemical Science and Technology
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• 제12권1호
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• pp.112-125
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• 2021

The new emerging "High entropy materials" attract the attention of the scientific society because of their simpler structure and spectacular applications in many fields. A novel nanocrystalline high entropy (Be,Mg,Ca,Sr,Zn,Ni)3O4 oxide has been successfully synthesized through mechanochemical treatment followed by sintering and air quenching. The present research work focuses on the possibility of single-phase formation in the aforementioned high entropy oxide despite the great difference in the atomic sizes of reactant alkaline earth and 3d transition metal oxides. Structural properties of (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide were explored by confirmation of its single-phase Fd-3m spinel structure by x-ray diffraction (XRD). Further, nanocrystalline nature and morphology were analyzed by scanning electron microscopy (SEM). Among thermal properties, thermogravimetric analysis (TGA) revealed that the (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide is thermally stable up to a temperature of 1200℃. Whereas phase evolution in (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide before and after sintering was analyzed through differential scanning calorimetry (DSC). Electrochemical studies of (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide consists of a comparison of thermodynamic and kinetic parameters of water and hydrazine hydrate oxidation. Values of activation energy for water oxidation (9.31 kJ mol-1) and hydrazine hydrate oxidation (13.93 kJ mol-1) reveal that (Be,Mg,Ca,Sr,Zn,Ni)3O4 high entropy oxide is catalytically more active towards water oxidation as compared to that of hydrazine hydrate oxidation. Electrochemical impedance spectroscopy is also performed to get insight into the kinetics of both types of reactions.