A spectrophotometric study of samarium (III) speciation in chloride solutions at elevated temperatures

An experimental study of the solubility and speciation of the Rare Earth Elements (III) in fluoride- and chloride-bearing aqueous solutions at temperatures up to 300°C

“…Table 1 and Fig. 4 compare the results of this study with those obtained in our earlier studies of the systems, Nd-F-H 2 O (Migdisov and Williams-Jones, 2007), Nd-Cl-H 2 O (Migdisov and Williams-Jones, 2002), Sm-Cl-H 2 O (Migdisov et al, 2008), and Er-Cl-H 2 O (Migdisov and WilliamsJones, 2006). From Fig.…”

“…Although the stability constant for NdCl 2+ determined experimentally by Gammons et al (1996) and Migdisov and Williams-Jones (2002) is less than half an order of magnitude higher than that predicted by the data of Haas et al (1995), it is about two orders of magnitude higher than predicted by Wood (1990a). Similar discrepancies are evident for samarium and erbium chloride species (Migdisov and Williams-Jones, 2006;Migdisov et al, 2008).…”

“…and HCl (Fisher Scientific, Optima grade). As REE(III) chloride species are considered to be only moderately stable (e.g., Migdisov et al, 2008), the chloride-bearing solutions were prepared to have a wide range of total chloride concentration (up to 1.57 m), in order to ensure reliable evaluation of the effect of chloride-ion activity on solubility. As was the case for fluoride, the concentration of chloride in the quenched experimental solutions was determined using INAA (É cole Polytechnique, Montréal).…”

“…The values for the distances of closest approach employed in the activity model (Eq. (1), NaCl/ HCl activity model; Helgeson et al, 1981;Oelkers and Helgeson, 1990) for REECl 2+ and REECl 2 + were set at 4.5 Å (Gammons et al, 1996;Migdisov et al, 2008). At this stage of the treatment, the adjustable parameters were the formation constants of the corresponding REE-chloride species:…”

Comment on “An experimental study of the solubility and speciation of neodymium (III) fluoride in F-bearing aqueous solutions” by A.A. Migdisov and A.E. Williams-Jones

“…WilliamsJones (hereafter M&WJ) and co-workers have been engaged in a very worthwhile endeavor to directly quantify stability constants at elevated temperatures for complexes of single rare earth elements (REEs) with chloride and sulfate, by means of a versatile spectrophotometric method which they adapted for this purpose (M&WJ, 2002(M&WJ, , 2006Migdisov et al, , 2008. Using a different and more interpretively challenging approach (e.g., Johansson, 1968), M&WJ recently investigated the solubility of neodymium (III) fluoride to obtain the NdF 3 (s) solubility product, log K sp , as well as the stability constant of the NdF 2+ -complex, log b 1 , at water saturation pressure and T = 150, 200, and 250°C (M & WJ, 2007).…”