• Bulletin of the Korean Chemical Society
• /
• v.28 no.8
• /
• pp.1329-1334
• /
• 2007

The electrochemical oxidation of cerium(III) was carried out using divided and undivided electrochemical cells in nitric acid medium. It was found that divided cell with Nafion 324 as the separator gave good conversion yield with high current efficiency compared to the undivided cell. The efficiency of the divided electrochemical cell was further optimized in terms of cell voltage, temperature, flow rate of solution recirculation, concentrations of Ce(III) and nitric acid. The better conditions for 1 M Ce(III) in 3 M nitric acid were found to be 2.5 V, 363 K and 100 mL/min recirculation flow rate based on the current efficiency under the experimental conditions investigated. The Ce(IV) oxidant produced was used as a mediator for the mineralization of phenol. The mineralization efficiency of the cerium mediated electrochemical oxidation was found rapid and higher compared to the direct electrochemical oxidation based on CO2 evolution under the same conditions.

• Nuclear Engineering and Technology
• /
• v.32 no.4
• /
• pp.309-315
• /
• 2000

The changes of Np oxidation state in nitric acid and the effect of nitrous acid on the oxidation state were analyzed by spectrophotometry, solvent extraction, and electrochemical methods. An enhancement of Np extraction to 30 vol.% TBP was carried out through adjustment of Np oxidation state by using a glassy carbon fiber column electrode system. The information of electrolytic behavior of nitric acid was important because the nitrous acid affecting the Np redox reaction was generated during the electrolytic adjustment of the Np oxidation state. The Np solution used in this work consisted of Np（V) and Np（Ⅵ）without （IV）. The composition of Np（V) in the range of 0.5M -5.5 M nitric acid was 32% ~ 19%. The electrolytic oxidation of Np（V) to Np（Ⅵ）in the solution enhanced Np extraction efficiency about five times higher than the case without the electrolytic oxidation. It was confirmed that the nitrous acid of less than about 10-5 M acted as a catalyst to accelerate the chemical oxidation reaction of Np（V) to Np（Ⅵ）.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.12
• /
• pp.4258-4260
• /
• 2012

• Bulletin of the Korean Chemical Society
• /
• v.22 no.1
• /
• pp.120-122
• /
• 2001

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.5
• /
• pp.341-344
• /
• 2018

In order to achieve a high efficiency for the silicon solar cell, a passivation characteristic that minimizes the electrical loss at a silicon interface is required. In this paper, we evaluated the applicability of the oxide film formed by ozone for the tunnel silicon oxide film. To this end, we fabricated the silicon oxide film by changing the condition of ozone oxidation and compared the characteristics with the oxide film formed by the existing nitric acid solution. The ozone oxidation was formed in the temperature range of $300{\sim}500^{\circ}C$ at an ozone concentration of 17.5 wt%, and the passivation characteristics were compared. Compared to the silicon oxide film formed by nitric acid oxidation, implied open circuit voltage (iVoc) was improved by ~20 mV in the ozone oxidation and the ozone oxidation after the nitric acid pretreatment was improved by ~30 mV.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.4
• /
• pp.972-974
• /
• 2009

• Resources Recycling
• /
• v.7 no.3
• /
• pp.17-26
• /
• 1998

A study on the recovery of silver and nitric acid in the liquid waste resulted from the mediated electrochemical oxidation(MEO) process was conducted. The removal of silver in the concentrated nitric acid solutions was carried out by the electrodeposition. The removal efficiency more than 98% could be obtained in nitric acid concentrations less than 3 M with the current efficiency of nearly 100%. The experimonts on the evaporation for the recovery of nitric acid were performed as well. At the evaporation factor of 25., the degree of nitric acid recovery in 3.5 M nitric acid solution containing 0.5 to 1.0 mol% NaNO, was 80~90% resulting in 2.8~3.1 M nitric acid. The design factors and operating conditions of the distillation tower were analyzed by using MEH model derived by Maphtali-Sandholm with the throughput of 4 kg/hr for the enrichment of dilute nitric acid solution recovered by evaporation to reuse in the MEO process. The distillation column composed of eleven theoretical stages having the overall tray efficiency of 70% are needed to obtain 1.03 kg/h of 12M nitric acid and 2.97 kg/h of water with feed being introduced to the column at tray 6 from the bottom at the reflux ratio of 0.25, the reboiler with the heat load of 2.7 kW, and the condenser with the cooling load of 0.5 kW.

• The Korea Journal of Herbology
• /
• v.22 no.2
• /
• pp.51-63
• /
• 2007

Objectives : For the congenital feeble, the Gongjindan is useful medicine. The experiment is to estimate the value of the Gongjindan as therapeutic agent preventing against aging with an analysis of the ingredients and the bio-activating effects by enzymologic methods. Methods : General ingredients' of the Gongjindan's extract were analyzed first and the quantitative analysis of a reducing sugar, a soluble protein, an amino acid and minerals was made. The Gongjindan, which is extracted, concentrated, and freeze drying with water, ethanol and chloroform, have got applied for the experiment. The effects on electronic donating ability, SOD-like activity, nitric oxide inhibition, xanthine oxidase inhibition, whitening effect have been investigated in the physiological activity measurement of function experiment. Results : The contained amino acid, in order of high amount, is Arginine, Alanine, Glutamic acid, Proline and the contained free amino acid is Glutamic acid, Leucine, Lysine, Phenylalanine. The derivative of free amino acid is ${\gamma}-Aminoisobutyric$ acid, Phosphoserine, Taurine. And the Gongjindan is containing 13 species of minerals in order of Ca>K>Na>Mg>Fe>AI>Mn. Then, to assure of the Gongjindan's capability of anti-oxidation, these following subjects-polyphenol, electronic donating ability, SOD-like activity, nitric oxide inhibition, xanthine oxidase inhibition, tyrosinase inhibition- are analyzed and show high activity especially the most in ethanol extracts. Conclusion : With this analysis of ingredients, the Gongjindan is containing many materials functioning as anti-oxidation, anti-aging, anti-fatigue, neurotransmitter and immune agent. Moreover, In every water, ethanol, chloroform extracts, the Gongjindan's capability of anti-oxidation is confirmed so that we can apply to patients' treatment clinically.

• Journal of the Korea Institute of Building Construction
• /
• v.14 no.4
• /
• pp.359-368
• /
• 2014

Photocatalytic cement has been receiving attention due to its high oxidation power that reduces nitrogen oxide, thus contributing to a clean atmospheric environment. However, there has not yet been a thorough investigation on the effect of photocatalytic reactions on the durability of cementitious material, the parent material. In this study, photocatalytic cement samples were exposed to nitric oxide gas and UV along with cycles of wetting and drying to simulate environmental conditions. The surface of samples was characterized mechanically, chemically, and visually during the cycling. The results indicate that that the photocatalytic efficiency decreased with continued NO oxidation. The pits found from SEM indicated that chemical deterioration, such as acid attack or leaching, did occur. However, this was not confirmed by X-ray diffraction. The hardness was not affected, probably due to the formation of CSH as evidenced by the XRD pattern. In conclusion, it was found that photocatalysis could alter cementitious materials both chemically and mechanically, which could further affect long-term durability.

• Nuclear Engineering and Technology
• /
• v.54 no.9
• /
• pp.3580-3585
• /
• 2022

The thermal stability of carbohydrazide, hydrazine nitrate, acetohydroxamic acid in nitric acid solutions has been studied at atmospheric pressure and above atmospheric pressure. The volumes of gaseous products of thermolysis and the maximum rate of gas evolution have been determined at atmospheric pressure. It has been shown that, despite the high rate of gas evolution and large volumes of evolved gases, the conditions for the development of autocatalytic oxidation are not created. Exothermic processes are observed in a closed vessel in the temperature range of 50-250 ℃. With an increase in the concentration of nitric acid, the temperatures of the onset of exothermic effects for all mixtures decrease, and the values of the total thermal effects of reactions increase, to the greatest extent for solutions with carbohydrazide.