Effects of Ionic Strength and Charge Density on the Stability of Chloride Complexes of Trivalent Lanthanides

Abstract

The stability constants of chloride complexes of trivalent praseodymium, europium, erbium, and lutetium (βLn,Cl I and βLn,2Cl I ) were determined at 303 K in a mixture of HClO4 and HCl media (ionic strength between (1 and 4) mol·dm−3) by means of a solvent extraction method using dinonyl napthalene sulfonic acid. Praseodymium and erbium concentrations were measured by a VIS spectrophotometric method using xylenol orange at pH 6, whereas radioactivity measurements were undertaken for europium and lutetium. The specific ion interaction theory (SIT) was applied for the calculation of log10 βLn,Cl 0, and a general view of the behavior of the first chloride constants against charge density of lanthanides was obtained.

On the Hydration of Heavy Rare Earth Ions: Ho3+, Er3+, Tm3+, Yb3+ and Lu3+—A Raman Study

“…(Quantitative Raman spectroscopy applied to these solution spectra with weak and broad low frequency bands is not very precise and therefore a higher uncertainty results.) Data from thermodynamic and spectroscopic studies on YbCl 3 (aq) solutions confirm the weak nature of the complex species [29,30,31,32]. The results on aqueous LuCl 3 solutions and similar rare earth systems [17,29,30,31,32] confirm our findings on YbCl 3 solutions.…”

“…Furthermore, a current study in the terahertz frequency range of YbCl 3 solutions using FT-IR spectroscopy [35] confirmed weak contact ion pairs as do our recent Raman results on LuCl 3 (aq) [17]. Choppin and Unrein [36] claimed that only outer-sphere ions pairs exist in lanthanide chloride solutions, but such a view has been questioned [17,29,30,31,32].…”

“…From thermodynamic measurements, it is known that Lu 3+ and Yb 3+ form weak chloro-complexes/ion-pairs [29,30,31,32]. As a model system for the HRE ion hydrates, aqueous YbCl 3 solutions were investigated.…”

X-ray Reflectivity Reveals a Nonmonotonic Ion-Density Profile Perpendicular to the Surface of ErCl3 Aqueous Solutions

“…The number of chloride ions associated with a dissolved Er 3+ ion is known to depend on aqueous solution conditions, including anion concentration. ,− The association is more complex at a solution surface because of the inherent asymmetry and the resulting potential concentration inhomogeneities, which is treated in our MD simulations by the addition of an image-charge force. Here, implicit-solvent MD simulations are used to determine an averaged distribution of Cl – around Ln 3+ in the inhomogeneous surface region, thereby providing insight into the effect of image charge forces on the surface distribution of Ln 3+ .…”

Separation of ND(III), DY(III) and Y(III) by solvent extraction using D2EHPA and EHEHPA

“…The cations will form complexes with chloride ions to some extent in the aqueous phase. Stability constants for REE chlorides can be found in literature (Fernández-Ramirez et al, 2008;Haas et al, 1995;Luo and Byrne, 2001;Spahiu and Bruno, 1995;Wood, 1990). The REE chloride and hydroxide stability constants from the Medusa database are tabulated in Table 2 (Medusa, 2013).…”