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The Solvent Extraction of Uranium (VI) using Hydroxyalkylenediphosphonic Acids

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Author(s): M. Bouhoun Ali | A.Y. Badjah Hadj Ahmed | M. Attou | A.H. Elias | M.A. Didi

Journal: Journal of Applied Sciences
ISSN 1812-5654

Volume: 10;
Issue: 22;
Start page: 2905;
Date: 2010;
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Keywords: HHDPA | diphosphonic acids | Extraction | DHDPA | uranium

ABSTRACT
The solvent extraction of uranium (VI) from aqueous solutions has been investigated using hexadecylhydroxydiphosphonic acid (HHDPA, H4L1) and dodecylhydroxydiphosphonic acid (DHDPA, H4L2), which were synthesized and characterized by elemental analysis and by FT-IR, 1H NMR, 31P NMR spectroscopy. In this study, we propose a tentative assignment for the shifts of those two ligands and their specific complexes with uranium (VI). A spectroscopic analysis has showed that coordination of uranium (VI) takes place via oxygen atoms. We carried out the extraction of uranium (VI) from aqueous solutions by HHDPA and DHDPA in [carbon tetrachloride + 2-octanol (v/v: 90%/10%)] solutions at an aqueous to organic phase ratio (1/1) and at room temperature. The results showed that the extraction yields are more significant in the case of the HHDPA (92%) which is equipped with a hydrocarbon chain, longer than that of the DHDPA (88%). Logarithmic plots of the uranium (VI) distribution ratio vs. pHeq and the extractant concentration showed that the ratio of extractant to extracted uranium(VI) is 2:1. The metal complexes formed in organic phase are UO2(H3L1)2.2H2O and UO2(H3L2)2. 2H2O for HHDPA and DHDPA respectively. The equilibrium constants for the extraction of uranium(VI) were found to be 2 and 1.27 for HHDPA and DHDPA, respectively.
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