Nockemann Peter, Thijs Ben, Pittois Stijn, Thoen Jan, Glorieux Christ, Van Hecke Kristof, Van Meervelt Luc, Kirchner Barbara, Binnemans Koen
Laboratory of Coordination Chemistry, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, Belgium.
J Phys Chem B. 2006 Oct 26;110(42):20978-92. doi: 10.1021/jp0642995.
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.
质子化甜菜碱双（三氟甲基磺酰）亚胺是一种能够溶解大量金属氧化物的离子液体。这种金属溶解能力具有选择性。可溶解的有三价稀土氧化物、氧化铀（VI）、氧化锌（II）、氧化镉（II）、氧化汞（II）、氧化镍（II）、氧化铜（II）、氧化钯（II）、氧化铅（II）、氧化锰（II）和氧化银（I）。不溶或极难溶解的是氧化铁（III）、氧化锰（IV）、氧化钴以及氧化铝和二氧化硅。通过用酸性水溶液处理离子液体，可以将金属从离子液体中剥离出来。在将金属离子转移到水相后，离子液体可以循环再利用。双（三氟甲基磺酰）亚胺甜菜碱在高温下与水形成单相，而在55.5摄氏度以下会发生相分离（温度开关行为）。离子液体与水的混合物还表现出pH依赖性相行为：在低pH值下会出现两相，而在中性或碱性条件下则存在单相。通过密度泛函理论计算研究了甜菜碱阳离子和双（三氟甲基磺酰）亚胺阴离子以及阳离子-阴离子对的结构、能量学和电荷分布。
