Observations on the Rare Earths. LI. An Electrometric Study of the Precipitation of Trivalent Hydrous Rare Earth Oxides or Hydroxides.

Moeller, Therald; Kremers, Howard E.

doi:10.1021/j150438a004

Cited by 92 publications

(44 citation statements)

References 18 publications

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“…Indeed, pK^io calculated from Information given in [64] for other REE (Pr, Sm, Gd) and Y-hydroxides [32] also differ for up to more than 2 log Units from bulk of the literature data, suggesting a systematic error in [64] for all REE except La. The average of other pKJio values for freshly precipitated Nd(0H)3(s) (23.91 [54], 22.69 [62], 22.49 [63], 23.92 [70], 23.06 [71], and 23.97 [72]) yielded pK^io = 23.34 ± 0.55 (2 ct"_, of average). Two solubility studies performed on well crystalline Nd(0H)3(s) yielded nearly the same pKJio value of 26.0 [11] and 26.29 [73], which are consistent with the value of 25.65 for aged precipitated Nd(0H)3(s) from [24,74], but not with the value of 23.89 given by Akselrud [19], also for aged precipitated Nd hydroxide.…”

Section: Nd(0h)3(s)mentioning

confidence: 99%

Standard Thermodynamic Properties and Heat Capacity Equations for Rare Earth Element Hydroxides

1998

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Lanthanum / Neodymium / Hydroxide / Thermodynamic properties / Solubility SummaryStandard thermodynamic properties at 298.15 K, 1 bar and heat capacity equations for La(0H)3(s) and Nd(0H)3(s) were generated from thermochemical data available in the literature. Calculated solubility products of these crystalline hydroxides at 298.15 K were compared to those derived from critically assessed solubility and Potentiometrie measurements. Good agreement between the calculated and measured solubility was found for La(OH)3(s). In contrast, the Nd(OH)3(s) solubility at 298.15 K, calculated from thermochemical data, was more than one and half Orders of magnitude higher than that derived from experimental solubility data. This result shows that Nd^"^ is much less mobile in natural environments than previously thought and suggests that accepted Standard thermodynamic properties for the Nd'^ aqueous ion at 298.15 K, 1 bar [2] need to be re-examined. By calculating equilibria between La-and Nd-crystalline hydroxides, hydroxycarbonates and carbonates we show in this study that Ln-hydroxides are the stable phases at low CO2 partial pressures typical for concrete backfill environments in proposed radioactive waste storage sites.

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Section: Nd(0h)3(s)mentioning

confidence: 99%

Standard Thermodynamic Properties and Heat Capacity Equations for Rare Earth Element Hydroxides

1998

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“…However, for Lu(III) an antisynergism was observed to occur when the distribution coefficient decreases by a factor of one thousand upto pH 6, and as a consequence there is a sharp decrease in the synergic coefficient (S.C.). In an investigation [7] it has been reported that the precipitation incidence occurs, for both Yb and Lu, at pH values greater than 6 and thus the hydrolysis of these rare earth elements is ruled out in the pH ränge of 3 to 6.…”

Section: Resultsmentioning

confidence: 99%

Effect of a Tertiary Amine on the Synergic Extraction of Lanthanides by Thenoyltrifluoroacetone (HTTA)

et al. 1992

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Synergie extraction of Yb(III) and Lu(III) has been carried out with thenoyltrifluoroacetone (HTTA) and tribenzylamine (TBA) in Chloroform from aqueous Perchlorate media from pH 1 to 6. The results demonstrate antisynergic effect from pH 3 to 6 in the extraction of Lu(III). The stoichiometric composition at pH 3 was established to be M(TTA)3 • 3TBA, where M = Yb(III) and Lu(III). However, the composition of synergic adducts at pH 6 was Yb(TTa)3 • 3TBA and Lu(TTA)3 • TBA. The change in the coordination number of the synergic adduct of Lu(III) at different pHs was further investigated through thermodynamic functions like enthalpy, entropy and Gibbs free energy. The mechanism of synergism and antisynergism of the synergic adducts at pH 3 and 6 has been discussed. The formation and stability constants have been determined.

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“…As the solution ages, the colloidal particles agglomerate and become less soluble, which is reflected by a decrease in pH and a corresponding increase in pK For freshly Sp" precipitated Gd(OH)~, the pKsp is 21.7 [12]. For Gd(OH)~aged 200 days, the pK5P is 26.88 [13].…”

Section: Resultsmentioning

confidence: 99%

Preparation and properties of nitrate-deficient gadolinium nitrate solutions

Baumann

1980

Journal of Inorganic and Nuclear Chemistry

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-Gadolinium nitrate solutions (%0.00IM) were made nitrate-deficient by contact with hydroxyl-form anion exchange resin. These metastable solutions aged with a decrease in pH and in the amount of soluble gadolinium. Gamma irradiation with '°Co increased the rate of aging. Nitrate deficiency was qualitatively detected and quantitatively determined. At w23"C, the volubility product constant, K of gadolinium hydroxide in Sp' an aged and irradiated solution in HzO was 10 '26"8; for an aged solution in D20, K

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Observations on the Rare Earths. LI. An Electrometric Study of the Precipitation of Trivalent Hydrous Rare Earth Oxides or Hydroxides.

Cited by 92 publications

References 18 publications

Standard Thermodynamic Properties and Heat Capacity Equations for Rare Earth Element Hydroxides

Standard Thermodynamic Properties and Heat Capacity Equations for Rare Earth Element Hydroxides

Effect of a Tertiary Amine on the Synergic Extraction of Lanthanides by Thenoyltrifluoroacetone (HTTA)

Preparation and properties of nitrate-deficient gadolinium nitrate solutions

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