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The extraction of uranium(VI) from aqueous solutions has been investigated using 1-hydroxyhexadecylidene-1,1-diphosphonic acid (HHDPA) and 1-hydroxydodecylidene-1, 1-diphosphonic acid (HDDPA), which were synthesized and characterized by elemental analysis and by FT-IR, 1 H NMR, 31 P NMR spectroscopy. In this article, we propose a tentative assignment for the shifts of those two ligands and their specific complexes with uranium(VI). We carried out the extraction of uranium(VI) by HHDPA and HDDPA from [carbon tetrachloride + 2-octanol (v/v: 90%/10%)] solutions. Various factors such as contact time, pH, organic/aqueous phase ratio, and extractant concentration were considered. The optimum conditions obtained were: contact time = 20 min, organic/aqueous phase ratio = 1, pH value = 3.0, and extractant concentration = 0.3 M. The extraction yields are more significant in the case of the HHDPA which is equipped with a hydrocarbon chain, longer than that of the HDDPA. Logarithmic plots of the uranium(VI) distribution ratio vs. pH eq and the extractant concentration showed that the ratio of extractant to extracted uranium(VI) (ligand/metal) is 2:1. The formula of the complex of uranium(VI) with the HHDPA and the DHDPA is UO 2 (H 3 L) 2 (HHDPA and DHDPA are denoted as H 4 L). A spectroscopic analysis showed that coordination of uranium(VI) takes place via oxygen atoms.

023ChemInform Abstract The reaction between (CoW12O40)5-and sulfite is studied in the pH range 1.5-3.5 at 25 rc C and a ionic strength of 0.5 M (NaClO4). The stoichiometric results show that one-electron reduction of the complex by S(IV) is preferred at high S(IV) concentrations, while a two-electron reduction is observed simultaneously with the one-electron reduction when an excess of the Co(III) complex is used. A redox mechanism is proposed and discussed.