Thermodynamic Properties of Ternary Solutions in the Water–Nitric Acid–Rare Earth Nitrate (Pr, Nd, Sm) Systems at 298.15 K

Abstract

The vapor pressure measurement unit from borosilicate glass was assembled for determination of partial pressures of water in aggressive acidic media using the transpiration method. Three ternary systems H2O–HNO3–RE­(NO3)3 (RE = Pr, Nd, Sm) were investigated. The experimental results in ternary systems were compared with the estimation by the Pitzer model and Zdanovsky rule from the data of binary subsystems. In addition to vapor pressure measurements densities of investigated solutions were determined.

Modeling the Solution Properties and Mineral–Solution Equilibria in Radionuclide-Bearing Aqueous Nitrate Systems: Application to Binary and Ternary Systems Containing U, Th, or Lanthanides at 25 °C

“…Further works should investigate Ln–NO 3 –H 2 O mixed with nitric acid as there is industrial interest for the recovery of REEs. ,, Moiseev et al measured the water vapor partial pressure above aqueous solutions of Ln­(NO 3 ) 3 (where Ln = Pr, Nd, or Sm) mixed with nitric acid. Ln­(NO 3 ) 3 concentrations varied from 0.1 to 2.9 M and nitric acid concentrations varied up to 15 M. The set of Pitzer specific interaction parameters proposed in the present work and its companion articles , can describe the experimental data of Moiseev et al without additional ternary interaction parameters (Figure , with σ = 0.011 for 27 data points). Indeed, as indicated by these authors, the ZSR rule applies for such chemical systems when the chemical composition is relatively far from the solubility limits.…”

“…Comparison between experimental and calculated activity of water, a w , for aqueous solutions in the Ln­(NO 3 ) 3 –HNO 3 aqueous mixtures (with Ln = Pr, Nd, or Sm), at 25 °C (symbols). The straight dotted line shows the first bisector representing an equality between experimental and calculated values.…”

“…16,41,42 Moiseev et al 41 measured the water vapor partial pressure above aqueous solutions of Ln(NO 3 ) 3 (where Ln = Pr, Nd, or Sm) mixed with nitric acid. Ln(NO 3 ) 3 concentrations varied from 0.1 to 2.9 M and nitric acid concentrations varied up to 15 M. The set of Pitzer specific interaction parameters proposed in the present work and its companion articles 17,18 can describe the experimental data of Moiseev et al 41 without additional ternary interaction parameters (Figure 20, with σ = 0.011 for 27 data points). Indeed, as indicated by these authors, the ZSR rule applies for such chemical systems when the chemical composition is relatively far from the solubility limits.…”

Thermodynamic Modeling of Multicomponent Rare Earth Nitrates Aqueous Systems

“…Dealing with the same, Chatterjee et al [21] wrongly assumed that the Pitzer model describes osmotic coefficients well but not the mean ionic activity coefficients at ionic strengths greater than 4 mol/kg. It was nevertheless shown in [22] that an error was made in the calculations of [21] (the dependence of parameter C cx of the Pitzer model on concentration was not considered). Introducing it allows to describe the activity coefficients up to an ionic strength of 20 mol/kg.…”