کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
11025078 | 1701032 | 2018 | 15 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Redox chemistry of uranium in reducing, dilute to concentrated NaCl solutions
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The redox behaviour of uranium was investigated in 0.1 and 5.0â¯M NaCl solutions at 2 ⤠pHmâ¯â¤â¯14.5 (pHmâ¯=â¯-logâ¯[H+]) in the presence of different reducing chemical systems (Sn(II), Na2S2O4, Sn(II) + TiO2, Sn(II) + Fe(0), Sn(II) + Fe3O4). All experiments were performed under Ar atmosphere at T = (22â¯Â±â¯2) °C. Uranium was added to independent batch samples as U(VI) (with [U]0â¯=â¯3.0â
10â5 or 4.2â
10â4â¯M), and the evolution of uranium concentration monitored for tâ¯â¤â¯635 days. After attaining equilibrium conditions, [U] was found in all cases clearly below the solubility of U(VI) solid phases (UO3â
2H2O(cr) or Na2U2O7â
H2O(cr)) and in good agreement with the solubility of tetravalent UO2(am, hyd) as calculated with available thermodynamic data. This observation is in line with (pe + pHm) measurements, which in all cases fell in the stability field of U(IV). Solvent extraction and XANES confirmed also that uranium is predominantly found as U(IV) in the aqueous and solid phases investigated. No evidence on the formation of anionic hydrolysis species of U(IV) was obtained up to pHmâ¯=â¯14.5. Based on our long-term redox study, we conclude that previous investigations reporting the formation of U(OH)5- and U(OH)62â are possibly flawed by insufficient equilibration time, which prevented the complete reduction of U(VI) to U(IV). Our results further confirm that experimental pHm and Eh values measured in buffered systems can be considered as reliable parameters to predict the redox behaviour of U in dilute to concentrated NaCl systems.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Applied Geochemistry - Volume 98, November 2018, Pages 286-300
Journal: Applied Geochemistry - Volume 98, November 2018, Pages 286-300
نویسندگان
NeÅe Ãevirim-Papaioannou, Ezgi YalçıntaÅ, Xavier Gaona, Kathy Dardenne, Marcus Altmaier, Horst Geckeis,