Extraction and thermodynamic behavior of U(VI) and Th(IV) from nitric acid solution with tri-isoamyl phosphate |
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| Authors: | Fang Kong Jia-li Liao Song-dong Ding Yuan-you Yang Huang Huang Ji-jun Yang Jun Tang Ning Liu |
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| Institution: | 1. Key Laboratory of Radiation Physics and Technology, Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, China
2. College of Chemistry, Sichuan University, Chengdu, 610064, China
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| Abstract: | The extraction behavior of U(VI) and Th(IV) with tri-isoamyl phosphate–kerosene (TiAP–KO) from nitric acid medium was investigated in detail using the batch extraction method as a function of aqueous-phase acidity, TiAP concentration and temperature, then the thermodynamic parameters associated with the extraction were derived by the second-law method. It could be noted that the distribution ratios of U(VI) or Th(IV) increased with increasing HNO3 concentration until 6 or 5 M from 0.1 M. However, a good separation factor (D U(VI)/D Th(IV)) of 88.25 was achieved at 6 M HNO3, and the stripping of U(VI) from TiAP–KO with deionized water or diluted nitric acid was easier than that of Th(IV). The probable extracted species were deduced by log D-log c plot at different temperatures as UO2(NO3)2·(TiAP)(1–2) and Th(NO3)4·(TiAP)(2–3), respectively. Additionally, △H, △G and △S for the extraction of U(VI) and Th(IV) revealed that the extraction of U(VI) by TiAP was an exothermic process and was counteracted by entropy change, while the extraction of Th(IV) was an endothermic process and was driven by entropy change. |
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