title: Task-specific ionic liquid for solubilizing metal oxides.
abstract: Protonated betaine bis(trifluoromethylsulfonyl)imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium(II) oxide, mercury(II) oxide, nickel(II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese(II) oxide, and silver(I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis(trifluoromethylsulfonyl)imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C (temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis(trifluoromethylsulfonyl)imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.
authors.affiliation: Laboratory of Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Nockemann
authors.forename: Ben
authors.initials: B
authors.lastname: Thijs
authors.forename: Stijn
authors.initials: S
authors.lastname: Pittois
authors.forename: Jan
authors.initials: J
authors.lastname: Thoen
authors.forename: Christ
authors.initials: C
authors.lastname: Glorieux
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Hecke
authors.forename: Luc
authors.initials: L
authors.lastname: Van Meervelt
authors.forename: Barbara
authors.initials: B
authors.lastname: Kirchner
authors.forename: Koen
authors.initials: K
authors.lastname: Binnemans
mesh_terms: D003247:Conservation of Natural Resources; D006863:Hydrogen-Ion Concentration; D052578:Ionic Liquids / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D012995:Solubility; D014867:Water
chemical_list: D052578:Ionic Liquids; D019216:Metals, Heavy; D010087:Oxides; D014867:Water