• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.2
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• pp.93-100
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• 2009

This study has been carried out to look into the characteristics of an oxidative-dissolution of fission products (FP) co-dissolved with uranium (U) in a $(NH_4)_2CO_3$ carbonate solution. Simulated FP-oxides which contained 12 components have been added to the solution to examine their dissolution characteristics. It is found that $H_2O_2$ is an effective oxidant to minimize the oxidative-dissolution of FP. In the 0.5 M $(NH_4)_2CO_3$-0.5 M $H_2O_2$ solution, some elements such as Re, Te, Cs and Mo seem to be dissolved together with U, while 98${\pm}$2% for Re and Te, 94${\pm}$2% for Cs, and 29${\pm}$2 % for Mo are dissolved for 2 hours. It is revealed that dissolution rates of Re, Te and Cs are high (completely dissolved within 10${\sim}$20 minutes) due to their high solubility in the $(NH_4)_2CO_3$ solution regardless of the addition of $H_2O_2$, and independent of the concentrations of $Na_2CO_3$ and $H_2O_2$. However, the dissolution ratio of Mo seems to be slightly increased with time and about 33 % for 4 hours, indicating a very slow dissolution rate and also independent of the $(NH_4)_2CO_3$ concentration. It is found that the most important factor for the oxidative-dissolution of FP is the pH of the solution and an effective dissolution is achieved at a pH between 9${\sim}$10 in order to minimize the dissolution of FP.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.77-85
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• 2012

This study was carried out to remove (/recover) the uranium from the Uranium-bearing Lime Precipitate (ULP). An oxidative dissolution of ULP with carbonate-acidified precipitation and a dissolution of ULP with nitric acid-hydrogen peroxide precipitation were discussed, respectively. In point of view the dissolution of uranium in ULP, nitric acid dissolution which could dissolved more than 98% of uranium was more effective than carbonate dissolution. However, in this case, uranium was dissolved together with a large amount of impurities such as Al, Ca, Fe, Mg, Si, etc. and some impurities were also co-precipitated with uranium during a hydrogen peroxide precipitation. On the other hand, in the case of carbonate dissolution-acidified precipitation, U was dissolved less than 90%. Therefore, it was less effective than nitric acid dissolution for the volume reduction of radioactive solid waste. However, it was very effective to recover the pure uranium, because impurities were hardly dissolved and hardly co-precipitated with uranium.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.43-47
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• 2003

산화환경에 노출된 폐광석에 포함되어 있는 황화광물은 산소와 물과의 화학반응을 통한 산화작용을 받게 되고 주변 환경에 유해한 금속원소의 용출이 발생될 것으로 예상된다. 그러나 용해된 금속이온은 침전(precipitation), 공침(coprecipitation), 흡착(adsorption)반응에 의해 수용액으로부터 제거되어 자연적으로 고정화될 수 있다. 이번 연구는 서보광산의 폐광석 내 용해된 중금속원소들의 이동을 제한하는 요인으로서 2차 산화광물의 침전 및 용해된 중금속 원소들의 흡착 가능성을 광물학적으로 연구하였다. (중략)

• Journal of the Mineralogical Society of Korea
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• v.13 no.2
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• pp.73-83
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• 2000

다덕 광산 폐석내 섬아연석과 함망간탄산염 광물의 풍화현상과 그에 따른 중금속의 거동을 조사 하였다. 섬아연석은 풍화초기에 극미립 산화철의 망상구조 집합체로 교대되었으며, 후기에는 자연황이 용해중인 섬아연석과 산화철 집합체 사이에 침전되었다. 산화철 집합체에는 As가 다량 함유되어 있다. 능망간석와 함망간 방해석은 함아연산화망간의 망상구조 집합체로 교대되었으며, 함망간방해서과 함아연산화망간 사이에는 스미소나이트가 침전되었다. 선택적 용해외 X선회절분석을 이용하여 감정한 결과, 함아연산화망간은 헤테롤라이트/하이드로헤테롤라이트인 것으로 판명되었다. Zn의 일부는 규산과 결합하여 입간 공극에 월레마이트로 침전되었다. 풍화 초기에 형성되는 극미립 산화철 및 함아연산화망간의 치밀한 망상 집합체는 풍화용액의 순환을 차단하여, 모광물의 풍화 반응을 지체시키는 지화학적 장벽 역할을 하였다. 이에 따라 망상구조 내에 조성된 국지적 미환경하에서 풍화중간산물들이 침전되었다. 이상의 연구 결과로 다음과 같은 사항을 추론할 수 있다. 섬아연석의 Fe와 함망간탄산염의 Mn은 각각 산화철과 산화망간으로 침전되어 산성화에 기여하였다. 폐광석 더미내 As의 활동도는 저결정질 산화철에의 흡착에 의해 조절되며, Zn의 활동도는 미소환경조건에 따라 하이드로헤테롤라이트/헤테롤라이트, 스미소나이트, 월레마이트 등의 다양한 이차광물의 용해도에 의하여 조절된다.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.576-584
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• 1994

The method described offers rapid and efficient sample preparation using on-line microwave digestion of metal oxides in water sample with direct elemental detection by ICP-AES. The open tubing digestion system(OTD) and the restraint tubing digestion system(RTD) for flow injection(FI) were designed and tested to find the optimum conditions. Comparison of OTD and RTD indicated that RTD was 3 times faster on the digestion time, and 10 times higher on sample mass. Finally, the results of RTD agree well with those by conventional microwave open vessel in all cases and show good precision; Fe and Cu show good with about 5% of RSD, while Zn and Co more or less than 10% RSD.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2001.06a
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• pp.171-174
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• 2001

식물의 대사과정을 통하여 흡수된 대기오염물질은 많은 단계의 해독과정 거치게 된다. SO$_2$ 의 경우는 세포질에서 그 대부분이 SO$_{3}$$^{2-}$ 로 용해되고 일부는 HSO$_{3}$ $^{-}$의 형태로 용해된다. 용해된 SO$_{3}$$^{2-}$ 는 아황산산화효소에 의해서 엽록체에서 생성된 $O_{2}$$^{-}$와 산화 반응하여 비교적 독성이 낮은 SO$_{4}$$^{2-}$ 로 변화한다.(중략)

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.159-164
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• 2008

We investigated chloride ion effects on anodic dissolution of copper using potentiodynamic method, cyclic voltammtery, chronoamperometry and chronocoulometry. The anodic dissolution reaction of copper in NaCl solution under argon atmosphere is $Cu+2Cl^{-}{\rightleftharpoons}{CuCl_2}^{-}+e^-$ and chloride ion adsorption process in copper surface can be explained by Temkin isotherm.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.4
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• pp.273-280
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• 2012

The electrochemical behaviors of 10 g-scale fresh and oxidized Zircaloy-4 cladding hulls were examined in $500^{\circ}C$ LiCl-KCl molten salts to confirm the feasibility of the electrorefining process for the treatment of hull wastes. In the results of measuring the potential-current response using a stainless steel basket filled with oxidized Zircaloy-4 hull specimens, the oxidation peak of Zr appears to be at -0.7 to -0.8 V vs. Ag/AgCl, which is similar to that of fresh Zircaloy-4 hulls, while the oxidation current is found to be much smaller than that of fresh Zircaloy-4 hulls. These results are congruent with the outcome of current-time curves at -0.78 V and of measuring the change in the average weight and thickness after the electrochemical dissolution process. Although the oxide layer on the surface affects the uniformity and rate of dissolution by decreasing the conductivity of Zircaloy-4 hulls, electrochemical dissolution is considered to occur owing to the defect of the surface and phase properties of the Zr oxide layer.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.155-162
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• 2012

We observed characteristic oxidation and dissolution phenomena induced by dissolved oxygen for mackinawite that is produced via sulfate-reducing bacteria (SRB) living in anaerobic environments such as soils and groundwater. We tried to recognize the role of the sulfide minerals that usually coexist with some stabilized radionuclides (e.g., reduced uranium), which can be reoxidized and redissolved by an oxygen-rich groundwater invaded into a contaminated area. The mackinawite produced by 'Desulfovibrio desulfuricans', a sulfate-reducing bacterium, was conducted to be dissolved for 2 weeks by some oxidants such as 'hydrogen peroxide' and 'sodium nitrite'. Although mineralogical oxidation and dissolution characteristics were different from each other according to the oxidants, the initially oxidized solution was early stabilized through the oxygen consumption by ${\mu}m$-sized sulfide particles and the resultant increase of sulfate in solution. From these results, we can anticipate that the large amount of sulfide minerals generated by SRB can not only repress the anoxic environment to be disturbed by the consumption of oxygen in groundwater, but also contribute to stabilize the reduced/precipitated radionuclides as a buffer material for a long time.

• Applied Biological Chemistry
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• v.34 no.1
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• pp.8-13
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• 1991

In order to investigate interactions of autoxidizing lipids with protein, enzyme and peroxidizing linoleate were reacted in freeze-dried and emulsion systems at various level of water activities. Peroxide value, TBA value of oxidized linoleate increased during incubation Solubilities and the activities of enzymes decreased as water activity increased.