Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System
Equilibrium of Nitrous Acid-Catalyzed Oxidation of Neptunium in Nitric Acid-TBP Extraction System
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DOI：
10.3327/jnst.32.50
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
O. Tochiyama;Yoshinobu;Nakamura;Yasushi;Katayama;Inoue
中科院分区：
文献类型：
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作者：
O. Tochiyama;Yoshinobu;Nakamura;Yasushi;Katayama;Inoue
在3 ~ 6 M硝酸溶液中，用30vol%TBP-十二烷萃取法研究了镎与硝酸和亚硝酸的氧化还原平衡，NpO ~（2+）+（3/2）H ~（++）（1/2）NO ~（3-）= NpO ~（2+）+（1/2）HNO ~（2+）（1/2）H_2 O。镎的平衡分配比可用D= D_6R/（1+R）表示，其中R为[Np（VI）]/[Np（V）]，D_6为纯Np（VI）的分配比。为了研究反应的表观浓度常数Kapp=[NP（VI）][HNO 2]1/2/[Np（V）][HNO 3]t2对硝酸浓度的依赖性，测定了HNO 3/HNO 2溶液的氧化还原电位，结果表明，对H+、NO3-、HNO 2和H2O的活度校正足以给出HNO 3/HNO 2电位的理想能斯特关系。用活度系数商，Y= ys 2/（yuaw）1/2（ys：硝酸的化学计量活度系数，yu：HNO 2的活度系数，aw：水的合理活度），表观浓度常数Kapp表示为Kapp=KmixY，其中Kmix=[Np（VI）]{HNO 2}1/2{H2O}1/2/[NP（V）]{H+}3/2{NO3-}1/2，对于[HNO 3]t=3、4和6 M，log Kmix=-2.77，log Y=-0.13，0.02和0.28。
The redox equilibrium of neptunium with nitric and nitrous acids, NpO2++(3/2)H++(1/2)NO3-=NpO22++(1/2)HNO2+(1/2)H2O was studied in 3 to 6M nitric acid solutions by 30vol% TBP-dodecane extraction. The equilib rium distribution ratio of neptunium was shown to be expressed by D=D6R/(1+R), where R is [Np(VI)]/[Np(V)] and D6 the distribution ratio of pure Np(VI). To examine the dependence of the apparent concentration constant for the reaction, Kapp=[NP(VI)][HNO2]1/2/[Np(V)][HNO3]t2 on nitric acid concentration, the redox potentials of HNO3/HNO2 solutions were measured which revealed that the activity correction on H+, NO3-, HNO2 and H2O was effective enough to give an ideal Nernst relationship for the potential of HNO3/HNO2. With using the activity coefficient quotient, Y=ys2/(yuaw)1/2(ys: stoichiometric activity coefficient of nitric acid, yu: activity coefficient of HNO2, aw: rational activity of water), the apparent concentration constant Kapp was shown to be expressed by Kapp=KmixY, where Kmix=[Np(VI)]{HNO2}1/2{H2O}1/2/[NP(V)]{H+}3/2{NO3-}1/2 and log Kmix=-2.77 and log Y=-0.13, 0.02 and 0.28 for [HNO3]t=3, 4 and 6M, respectively.