title: Competitive complexation of nitrates and chlorides to uranyl in a room temperature ionic liquid.
abstract: By coupling EXAFS, UV-vis spectroscopy, and molecular dynamics and quantum mechanical calculations, we studied the competitive complexation of uranyl cations with nitrate and chloride ions in a water immiscible ionic liquid (IL), C(4)mimTf(2)N (C(4)mim(+): 1-butyl-3-methyl-imidazolium; Tf(2)N(-) = (CF(3)SO(2))(2)N)(-): bis(trifluoromethylsulfonyl)imide). Both nitrate and chloride are stronger ligands for uranyl than the IL Tf(2)N(-) or triflate anions and when those anions are simultaneously present, neither the limiting complex UO(2)(NO(3))(3)(-) nor UO(2)Cl(4)(2-) alone could be observed. At a U/NO(3)/Cl ratio of 1/2/2, the dominant species is likely UO(2)Cl(NO(3))(2)(-). When chloride is in excess over uranyl with different nitrate concentrations (U/NO(3)/Cl ratio of 1/2/6, 1/4/4, and 1/12/4) the solution contains a mixture of UO(2)Cl(4)(2-) and UO(2)Cl(3)(NO(3))(2-) species. Furthermore, it is shown that the experimental protocol for introducing these anions to the solution (either as uranyl counterion, as added salt, or as IL component) influences the UV-vis spectra, pointing to the formation of different kinetically equilibrated complexes in the IL.
authors.affiliation: Institut de Physique Nucléaire de Lyon, CNRS-IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne cedex, France. c.gaillard@ipnl.in2p3.fr
authors.forename: C
authors.initials: C
authors.lastname: Gaillard
authors.forename: A
authors.initials: A
authors.lastname: Chaumont
authors.forename: I
authors.initials: I
authors.lastname: Billard
authors.forename: C
authors.initials: C
authors.lastname: Hennig
authors.forename: A
authors.initials: A
authors.lastname: Ouadi
authors.forename: S
authors.initials: S
authors.lastname: Georg
authors.forename: G
authors.initials: G
authors.lastname: Wipff