• 대한금속재료학회지
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• 제46권4호
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• pp.233-240
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• 2008

The reductive precipitation of platinum and palladium in hydrochloric acid solution using hydrazine as a reducing agent was investigated. The reductive precipitation ratios of platinum and palladium increased when increasing the stoichiometric ratio for reducing agent, precipitation time, and pH. The precipitation ratio of platinum was much lower than that of palladium. This is the reason the reaction rate of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}$ at the reduction reaction step of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}{\rightarrow}Pt$ is very slow. The purity of platinum precipitated was very affected by metallic impurities, while it was possible to precipitate the high purity palladium since the precipitation rate of palladium was relatively fast. At the pH of 1.3, the precipitation temperature of $25^{\circ}C$, and the addition amounts of the hydrazine of 10 and 1.75 times the stoichiometric ratio, the reductive precipitation ratios of platinum and palladium from their hydrochloric acid solutions containing 2,000 ppm were 98.5% and 99.9% in 30 min, respectively.

• 자원리싸이클링
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• 제14권6호
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• pp.21-27
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• 2005

국내 은 함유 폐자원의 고부가가치 제품화를 위한 연구의 일환으로써 sodium formaldehydesulfoxy와 ascorbic acid를 각각 환원제로 사용한 Ag 나노분발의 제조실험을 수행하였다. Ag수용액은 질산은을 소정 농도로 증류수에 용해시켜 사용하였으며, Ag미립자의 응집방지를 위한 분산제로는 Tamol NN8906, PVP, SDS 및 caprylic acid를 각각 사용하었다. 환원반응을 통하여 제조한 Ag 미립자는 입도분석기 및 TEM측정을 통하여 morphology와 평균입도를 측정하였다. sodium formaldehydesulfoxylate 에 의한 은의 환원을 위해서는 이론치의 1.4배를 첨가해 주어야 하는 것으로 나타났으며, ascorbic acid와는 달리 생성된 Ag 입자가 너무 크게 성장하는 문제점이 있었다. 분산제에 따른 Ag 입자의 특성을 살펴본 결과, Tamol 및 PVP를 사용한 경우에는 bimodal distribution을 보였으나, SDS 와 caprylic acid의 경우에는 수십 nm에서 $100{\mu}m$에 이르는 매우 broad한 입도분포를 보였다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 춘계학술논문요약집
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• pp.341-342
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• 2018

• 공업화학
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• 제10권7호
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• pp.996-1002
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• 1999

알칼리 및 알칼리토금속(Cs, Rb, Ba, Sr), 전이금속(Zr, Fe, Mo, Ni, Pd, Rh), 란탄족(La, Y, Nd, Ce, Eu) 및 악티늄족(Np, Am) 등 17개 원소로 구성된 질산매질의 모의 방사성용액에서 옥살산에 의한 란탄족과 악티늄족 원소의 공침전 연구를 수행하였다. 옥살산 농도 0.5 M에서 질산농도의 영향과 아스코빅산 첨가에 따른 원소들의 침전율이 조사되었다. 각 원소들의 침전율은 질산농도에 따라 약간 감소하였으나 란탄족과 악티늄족은 99% 이상 침전되었다. 옥살산 침전시 아스코빅산이 첨가되는 경우 Pd이 금속으로 환원 침전되었고, 이때 Mo, Fe, Ni, Ba의 경우는 침전율이 약 10~20% 감소하는 것으로 나타났으나, 기타 원소들에 대해서는 영향이 나타나지 않았다. Pd(II) 이온은 질산농도 1.0 M 미만의 모의용액에서 아스코빅산 첨가시 Pd 금속으로의 환원침전이 일어났으며, 아스코빅산 농도가 0.01~0.02 M 부근에서 가장 크게 나타났다. 하이드라진이 아스코빅산과 같이 첨가될 때 Pd의 환원침전을 억제하는 것으로 나타났다.

• 자원리싸이클링
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• 제15권4호
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• pp.19-26
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• 2006

함은 폐재의 리싸이클링을 위한 연구의 일환으로써 Hydrazine Hydrate을 환원제로 사용하여 질산은 수용액으로부터 Ag 나노분말을 제조하기 위한 실험을 수행하였다. 이를 위해 질산은을 소정 농도로 증류수에 용해시킨 수용액에 Ag 미립자의 응집방지를 위한 분산제로써 Tamol NN8906 혹은 Tween 20을 미리 혼합한 다음 환원제인 Hydrazine Hydrate 용액을 첨가하는 방법으로 환원반응을 실시하였다. 환원반응을 통하여 제조한 Ag 미립자는 입도분석기 및 TEM 측정을 통하여 형상과 평균입도를 측정하였다. Hydrazine Hydrate에 의한 은의 환원을 위해서는 이론치의 약 2배를 첨가해 주어야 하는 것으로 나타났으며, Tamol NN8906을 분산제로 사용하여 제조한 Ag 나노분발은 매우 좁은 입도범위의 분포특성을 보여 주었다. Tween 20을 분산제로 사용한 경우의 입도 분포는 bimodal 혹은 multimodal distribution을 보였으며, 입자 모양에 있어서는 Tamol NN8906과 Tween 20이 모두 비슷하게 표면이 매끄러운 불규칙한 모양의 입자들로 구성되어 있었다.

• 대한환경공학회지
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• 제30권12호
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• pp.1262-1267
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• 2008

영가금속을 이용한 아조계 염료의 탈색연구를 수행하였다. 아조계 염료는 대부분 생물학적 독성을 갖고 있으며 생물학적 분해가 어려운 경우가 많다. 색을 제거하기 위한 가장 간단한 방법은 아조결합을 파괴하는 것이며 영가금속을 이용한 환원적 제거가 가능하다. 3종의 염료를(Cibacron Briliant Yellow 3G-P (CBY3G-P), Benzopurpurin 4b (B-4B), Chicago sky blue 6b (CSB6B)) 대상으로 연구하였으며 각 염료의 반응속도는 pH에 매우 의존적이며 낮은 pH에서 반응속도가 증가되었다. 영가철에서 용해된 철이온에 의한 응집 및 침전반응도 색도제거에 기여할 수 있으며 본 연구에서는 그 기여율을 알기 위해 철이온에 의한 제거실험을 수행하였으며 그 기여율은 대상 염료에 따라 편차가 크다는 것을 알 수 있었다. 본 연구에서는 영가철에 의한 환원반응에 의해아조계 염료가 성공적으로 탈색될 수 있음을 증명하였다.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2543-2551
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• 2020

Calculations of chemical equilibrium for multicomponent aqueous systems of the HyBRID dissolution of magnetite were performed by using the HSC Chemistry. They were done by using a Pitzer-based aqueous solution model with the recipe of raw materials in experiments conducted at KAERI. The change in the amounts of species and ions and the pH values of the solution at equilibrium was observed as functions of temperature and raw amount of CuSO₄. Precipitation of Cu₂O occurred at a large amount of CuSO₄ added to the solution, while no precipitation of Cu(OH)₂ was found at any amounts of CuSO₄. The E-pH diagrams for Cu were constructed at various Cu concentrations to provide the effect of the Cu concentration on the pH values at boundaries where the coexistence of Cu⁺ ion and Cu₂O solid occurred. To prevent Cu⁺ ions from being precipitated to Cu₂O, the raw amount of CuSO₄ should be adjusted so that the pH value of the solution from the equilibrium calculation is less than that from the E-pH diagram. We provided guidelines for the raw amount of CuSO₄ and the pH value of the solution, which prevent the formation of Cu₂O precipitates in the HyBRID dissolution experiments for magnetite.

• Environmental Engineering Research
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• 제10권4호
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• pp.174-180
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• 2005

Nano-sized iron was synthesized using borohydride reduction of $Fe^{3+}$ in aqueous solution. A wide range of synthesis conditions including varying concentrations of reagents, reagent feeding rate, and solution pH was applied in an aqueous system under anaerobic condition. The reactivity of nano-sized iron from each synthesis was evaluated by reacting the iron with TCE in batch systems. Evidence obtained from this study suggest the reactivity of iron is strongly dependent on the synthesis solution pH. The iron reactivity increased as solution pH decreased. More rapid TCE reduction was observed for iron samples synthesized from higher initial $Fe^{3+}$ concentration, which resulted in lower solution pH during the synthesis reaction. Faster feeding of $BH_4^-$ solution to the $Fe^{3+}$ solution resulted in lower synthesis solution pH and the resultant iron samples gave higher TCE reduction rate. Lowering the pH of the solution after completion of the synthesis reaction significantly increased reactivity of iron. It is presumed that the increase in the reactivity of iron synthesized at lower pH is due to less precipitation of iron (hydr)oxides or less surface passivation of iron.

• Journal of Microbiology and Biotechnology
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• 제19권9호
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• pp.951-959
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• 2009

Most, if not all, Basidiomycetes mushrooms have biologically active polysaccharides showing potent antitumor activity with immunomodulating properties. These polysaccharides have various chemical compositions and belong primarily to the $\beta$-glucan group. In this study, the crude water-soluble polysaccharide HEF-P, which was obtained from the fruiting body of Hericium erinaceus by hot water extraction and ethanol precipitation, was fractionated by DEAE-cellulose and Sepharose CL-6B column chromatographies. This process resulted in four polysaccharide fractions, named HEF-NP Fr I, HEF-NP Fr II, HEF-AP Fr I, and HEF-AP Fr II. Of these fractions, HEF-AP Fr II was able to upregulate the functional events mediated by activated macrophages, such as production of nitric oxide and expression ofcytokines (IL-1${\beta}$ and TNF-${\alpha}$). The molecular mass of HEF-AP Fr II was estimated by gel filtration to be 13 kDa. Its structural characteristics were investigated by a combination of chemical and instrumental analyses, including methylation, reductive cleavage, acetylation, Fourier transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). Results indicate that HEF-AP Fr II is a low-molecular-mass polysaccharide with a laminarin-like triple helix conformation of a ${\beta}$-1,3-branched-${\beta}$-1,6-glucan.

• Journal of Microbiology and Biotechnology
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• 제20권7호
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• pp.1053-1060
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• 2010

Cordyceps militaris, an entomopathogenic fungus belonging to the class Ascomycetes, has been reported to have beneficial biological activities such as hypoglycemic, anti-inflammatory, antitumor, antimetastatic, hypolipidemic, immunomodulatory, and antioxidant effects. In this study, the crude water-soluble polysaccharide CMP, which was obtained from the fruiting body of C. militaris by hot water extraction and ethanol precipitation, was fractionated by DEAE-cellulose and Sepharose CL-6B column chromatographies. This process resulted in three polysaccharide fractions, termed CMP Fr I, CMP Fr II, and CMP Fr III. Of these fractions, CMP Fr II, with an average molecular mass of 127 kDa, was able to upregulate effectively the phenotypic functions of macrophages such as NO production and cytokine expression. The chemical property of the stimulatory polysaccharide, CMP Fr II, was determined based on its monosaccharide composition, which consisted of glucose (56.4%), galactose (26.4%), and mannose (17.2%). Its structural characteristics were investigated by a combination of chemical and instrumental analyses, including methylation, reductive cleavage, acetylation, Fourier transform infrared spectroscopy (FTIR), and gas chromatography-mass spectrometry (GCMS). Results indicated that CMP Fr II consisted of the (1${\rightarrow}$4) or (1${\rightarrow}$2) linked glucopyranosyl or galactopyranosyl residue with a (1${\rightarrow}$2) or (1${\rightarrow}$6) linked mannopyranosyl, glucopyranosyl, or galactopyranosyl residue as a side chain. The configuration of the ${\beta}$-linkage and random coil conformation of CMP Fr II were confirmed using a Fungi-Fluor kit and Congo red reagent, respectively.