Electrochemical Oxidation of Am(III) with Lacunary Heteropolyanions and Silver Nitrate

Formation Constants of Phosphotungstate Complexes of Europium(III)

“…Th(rV) seems to be an exception (there is no formation value for Th(IV), but adjunction of Th(IV) in Am(IV)/PWO mixtures leads to Th(IV)/PWO complexes formation [4]). In the same way, complexation of Ce(rV) (Th(IV) lanthanide analogue) seems to be very strong.…”

“…By this way, spectrum presented in Fig. 1 In comparison with other heteropolyanion complexes of lanthanides and actinides [1][2][3][4][5][6][7][8][9], it appears that the chemical species implying the Eu^^ cation and the PWO ligand have solely Eu(PWO) and Eu(PW0)2 stoichiometries. So the four peaks represented on the spectrum of the Fig.…”

“…Heteropolyanions are known to have selective and strong complexing properties towards tetravalent cations belonging to the f block Clements [1][2][3][4][5][6][7][8][9]. They form weaker complexes with trivalent "f" ions [7,9], and do not form complex with uranyl ion [1,9].…”

“…Further investigations on solid salts of U^(P2Wi706i)2'®" [2] and EU^CASJWI^OSOJ"" [3] complexes have shown that the coordination environment of U"^ and Eu'"^ in these Compounds, imposed by the two ligand groups (eight oxygen fonning a D4<, Square "Archimede's" antiprism), can explain the complexation of the "f" cations. Due to their highest charge density, complexes with M^^ ions such as Ce^^ [8], [1], Np^^ [7], Pu-'^ [1] or Am''^ [4] are considerably stronger than complexes with M"^ ions, such as Ce^^ [8], Nd'"^ [9] or Am^^ [5,7].…”

“…Actually, phosphotungstate and silicotungstate heteropolyanions are used to obtain higher oxidation State of americium, by stabilisation of +IV oxidation State of this actinide, in the context of lanthanide(III)/Am SESAME Separation program led at the CEA [4,10], In the domain of nuclear waste storage management, PWO heteropolyanion will be used in our laboratory as an Eu^^ cryptant ligand for TLRIS analytical development measurement in Sorption experiments.…”