Complexation of polyethylene glycol with Sr2+ and Ba2+ cations in extracts containing chlorinated cobalt dicarbollide

Abstract

The composition and structure of complexes that are formed in the system consisting of chlorinated cobalt dicarbollide (CCD), polyethylene glycol (PEG), and Sr 2+ or Ba 2+ in a polar diluent, dichloroethane or phenyl trifluoromethyl sulfone, were studied by IR and NMR spectroscopy. In extraction of Sr 2+ and Ba 2+ with solutions of [H 5 O + 2 . PEG]CCD ! , the organic phase contains the ionic associates [M 2+ . PEG]CCD 2 ! . The Sr 2+ and Ba 2+ complexes have similar composition and structure: The oxygen atoms of two OH groups and six COC groups of a PEG molecule fill the first coordination sphere of the metal ions. Also, no more than two water molecules can be coordinated in the second sphere, forming hydrogen bonds with the hydrogen atoms of two OH groups of PEG. The coordination of the OH groups of PEG with the Sr 2+ and Ba 2+ ions is preferable over the coordination of the COC groups, as follows from the fact that the extraction of Sr 2+ and Ba 2+ with CCD3PEG mixtures gets worse on replacement of the OH groups of PEG by other substituents. A considerable increase in the efficiency of Sr 2+ and Ba 2+ extraction with H-CCD solutions in the presence of PEG is due to the fact that all the H 2 O molecules in the first coordination spheres of the M 2+ ions are replaced by the COC and OH groups of PEG with the formation of a hydrophobic complex [M 2+ . PEG](H 2 O) 2 .

Fundamental Chemistry of Cesium Extraction from Acidic Media by HCCD in FS‐13

“…Furthermore, [HCCD] org represents the molar concentration of the free (unbound) HCCD at equilibrium. Equation (9) indicates that rather than plotting log D Cs as a function of the initial HNO 3 concentration, log (D Cs /g Cs ) versus log (a H þ/[HCCD] org ) should be plotted to obtain the theoretical slope of -1. Aside from the obvious simplification of working with a single equilibrium, equation (9) predicts that the Cs distribution data, spanning a range of HNO 3 and HCCD concentrations, can be treated simultaneously.…”

“…Equation (9) indicates that rather than plotting log D Cs as a function of the initial HNO 3 concentration, log (D Cs /g Cs ) versus log (a H þ/[HCCD] org ) should be plotted to obtain the theoretical slope of -1. Aside from the obvious simplification of working with a single equilibrium, equation (9) predicts that the Cs distribution data, spanning a range of HNO 3 and HCCD concentrations, can be treated simultaneously. Since SXLSQI calculates aqueous phase activity and activity coefficients for each data point and each ion based on the Pitzer treatment, [10] these g Csþ and a Hþ values can be conveniently used in the slope analysis.…”

“…Consequently, the organic phase species actually used in the above equilibria were HCCD(H 2 O) 5 , CsCCD(H 2 O) 6 , Cs þ (H 2 O) 6 , and 5 , which is also in accord with literature accounts of the organic phase hydration. [9] The significant errors on the values of K 3 and K 4 were attributed to uncertainties regarding the hydration number of the different dissociated species used in the model. The equilibrium constant for the primary exchange reaction (2) of log K eq ¼ 3.07 is in excellent agreement with the literature value of log K eq ¼ 3.00 for the HCCD/nitrobenzene system, albeit derived by different experimental and modeling schemes.…”

Equilibrium Speciation of Select Lanthanides in the Presence of Acidic Ligands in Homo- and Heterogeneous Solutions

“…As shown in Table 1.3, cesium and strontium and their daughter products barium and yttrium account for 71% of the total activity, but only 0.16% of the mass. Separation schemes using the chlorinated cobalt dicarbollide (CCD) with Polyethylene Glycol (PEG), [21][22] or calixarene type [23][24] molecules enable the selective extraction of cesium and strontium. The structures of the molecules used in cesium and strontium extraction are shown in Figure 1 UREX and NPEX processes.…”

“…Equilibrium speciation of neodymium (Nd 3+ ), sodium (Na + ), HDEHP, water, and lactate in the TALSPEAK liquid-liquid extraction system was explored under varied Nd 3+ loading of HDEHP in the organic phase and through extraction from aqueous HCl and lactate media. System speciation was probed through vapor pressure osmometry, visible and Fourier Transform Infrared (FTIR) spectroscopy, 22 Na and 13 C labeled lactate radiotracer distribution measurements, Karl Fischer titrations, and equilibrium pH measurements. Distribution of Nd 3+ , Na + , lactate, and equilibrium pH were modeled using the SXLSQI software to obtain logK Nd and logK Na extraction constants under selected conditions.…”