کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6438042 | 1638005 | 2015 | 13 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Neptunium redox speciation at the illite surface
ترجمه فارسی عنوان
تولید نانو پودر نیکل در سطح ایلیت
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
چکیده انگلیسی
Neptunium (Np(V)) sorption onto a purified illite is investigated as a function of pH (3-10) and [NpVO2+]tot(3 Ã 10â8-3 Ã 10â4 M) in 0.1 M NaCl under Ar atmosphere. After about one week reaction time, only insignificant variation of Np sorption is observed and the establishment of reaction equilibrium can be assumed. Surprisingly, solid-liquid distribution ratios (Rd) are clearly higher than those measured for Np(V) sorption onto illite under aerobic conditions. The observation that Rd increases with decreasing pe (pe = âlog aeâ) suggests partial reduction to Np(IV), although measured redox potentials (pe values) at a first glance suggest the predominance of Np(V). Reduction to Np(IV) at the illite surface could indeed be confirmed by X-ray absorption near-edge spectroscopy (XANES). Np speciation in presence of the purified Na-illite under given conditions is consistently described by applying the 2 sites protolysis non-electrostatic surface complexation and cation exchange model. Measured pe data are taken to calculate Np redox state and surface complexation constants for Np(IV) are derived by applying a data fitting procedure. Constants are very consistent with results obtained by applying an existing linear free energy relationship (LFER). Taking Np(IV) surface complexation constants into account shifts the calculated Np(V)/Np(IV) redox borderline in presence of illite surfaces by 3-5 pe units (0.2-0.3 V) towards redox neutral conditions. Our study suggests that Np(V) reduction in presence of a sorbing mineral phase is thermodynamically favored.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geochimica et Cosmochimica Acta - Volume 152, 1 March 2015, Pages 39-51
Journal: Geochimica et Cosmochimica Acta - Volume 152, 1 March 2015, Pages 39-51
نویسندگان
Rémi Marsac, Nidhu lal Banik, Johannes Lützenkirchen, Christian Michael Marquardt, Kathy Dardenne, Dieter Schild, Joerg Rothe, Alexandre Diascorn, Tomas Kupcik, Thorsten Schäfer, Horst Geckeis,