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RISS 인기검색어
- 검색키워드
- 저자 : (Robert J. Zasoski (검색결과 4 건)
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Soll Science , Fertilizer & Plant Nutrition : Oxidation of Cr(3) to Cr(4) by Pyrolusite
(Jong Bae Chung,(Robert J. Zasoski 한국응용생명화학회 2002 Journal of Applied Biological Chemistry (J. Appl. Vol.45 No.3
Chromium(Ⅲ) conversion to Cr(Ⅳ) in the presence of pyrolusite (β-MnO_2) was investigated at pHs3 and 5 with temperatures of 6 and 25℃, and ionic strengths of 0.1 and 0.001 M NaNo_3. The oxidation capacity of pyrolusite was relatively low in comparison to t
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Kinetics of Chromium(III) Oxidation by Various Manganess Oxides
정종배,임선옥,Chung, Jong-Bae,Zasoski, Robert J.,Lim, Sun-Uk 한국응용생명화학회 1994 Applied Biological Chemistry (Appl Biol Chem) Vol.37 No.5
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. Birnessite, pyrolusite and hausmannite were synthesized and tested for the ability to oxidize Cr(III) to Cr(VI). These oxides differed in zero point of charge, surface area, and crystallinity. The kinetic study showed that Cr(III) oxidation on the Mn-oxide surface is a first-order reaction. The reaction rate was various for different oxide at different conditions. Generally the reaction by hausmannite, containing Mn(III), was faster than the others, and oxidation by pyrolusite was much slower. Solution pH and initial Cr(III) concentration had a significant effect on the reaction. Inhibited oxidation at higher pH and initial Cr(III) concentration could be due to the chance of Cr(III) precipitation or complexing on the oxide surface. Oxidations by birnessite and hausmannite were faster at lower pH, but pyrolusite exhibited increased oxidation capacity at higher pH in the range between 3.0 and 5.0. Reactions were also temperature sensitive. Although calculated activation energies for the oxidation reactions at pH 3.0 were higher than the general activation energy for diffusion, there is no experimental evidence to suggest which reaction is the rate limiting step.
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정종배(Jong Bae Chung),임선옥(Sun Uk Lim),(Robert J . Zasoski) 한국응용생명화학회 1994 Applied Biological Chemistry (Appl Biol Chem) Vol.37 No.5
Birnessite, pyrolusite and hausmannite were synthesized and tested for the ability to oxidize Cr(Ⅲ) to Cr(Ⅵ). These oxides differed in zero point of charge, surface area, and crystallinity. The kinetic study showed that Cr(Ⅲ) oxidation on the Mn-oxide surface is a first-order reaction. The reaction rate was various for different oxide at different conditions. Generally the reaction by hausmannite, containing Mn(Ⅲ), was faster than the others, and oxidation by pyrolusite was much slower. Solution pH and initial Cr(Ⅲ) concentration had a significant effect on the reaction. Inhibited oxidation at higher pH and initial Cr(Ⅲ) concentration could be due to the chance of Cr(Ⅲ) precipitation or complexing on the oxide surface. Oxidations by birnessite and hausmannite were faster at lower pH, but pyrolusite exhibited increased oxidation capacity at higher pH in the range between 3.0 and 5.0. Reactions were also temperature sensitive. Although calculated activation energies for the oxidation reactions at pH 3.0 were higher than the general activation energy for diffusion, there is no experimental evidence to suggest which reaction is the rate limiting step.
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