Liquid–Liquid Equilibria in the Water–Nitric Acid–Europium Nitrate–Gadolinium Nitrate–Tributyl Phosphate System at 298.15 K

Extraction is a versatile and relatively simple method for extracting rare and scattered elements, producing good results at minimal expenses in terms of reagents and equipment. Information about the thermal effects and kinetic dependencies of the extraction process is essential for predicting and counteracting fluctuations in external conditions. In this work, the thermodynamic and kinetic parameters of the iodine extraction process were studied using model solutions that contained sodium chloride with an ionic strength of 0–5 mol/l as a background mineralization. This composition closely corresponds to natural and man-made waters of oil and gas condensate fields. A mixture of tri-n-butyl phosphate and isooctane was used as the extractant. In order to evaluate thermodynamic parameters, extraction isotherms were constructed at temperatures of 278 and 288 K. For different background ionic strength values, equilibrium extraction parameters were determined, including the extraction degree, distribution coefficient and equilibrium constant, as well as changes in the enthalpy, entropy and Gibbs energy of the process. A study of the kinetic dependencies of iodine extraction from aqueous solutions under different ionic strength values at temperatures of 278, 288 and 293 K allowed the true and apparent orders of reaction to be established, along with the activation energy of the extraction process. Across the entire range of the studied ionic strength values, iodine extraction occurs spontaneously with high distribution coefficients and an extraction degree of over 86%. The kinetic parameters of the iodine extraction process (activation energy, temporal and concentration reaction order) indicate the diffusion nature of the rate-determining step, the presence of intermediate complexation stages and the absence of temperature effects on the reaction rate.

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Phase Equilibria and Thermodynamic Properties of Phases in the H2O–Gd(NO3)3 System

Dzuban,

Novikov,

Nesterov

et al. 2023

Žurnal neorganičeskoj himii

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Solid–liquid equilibria in the system H2O–Gd(NO3)3 were measured from –20 to 70°C using the isothermal saturation method. The Pitzer–Simonson–Clegg thermodynamic model was implemented to obtain the temperature dependence of Gd(NO3)3⋅6H2O solubility constant, to calculate salt solubility and to construct a phase diagram of the system from eutectic point to hydrate melting. Thermochemical properties of gadolinium nitrate aqueous solutions, such as dilution enthalpies and heat capacities, were assessed also. The model has shown to be reliable for phase equilibria calculation from –35 to 90°C and from 0 up to ~15 mol % of salt as well as the thermodynamic properties of Gd(NO3)3 aqueous solutions at room temperature and around it.

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Liquid–Liquid Equilibria in the Water–Nitric Acid–Europium Nitrate–Gadolinium Nitrate–Tributyl Phosphate System at 298.15 K

Cited by 3 publications

References 31 publications

Phase Equilibria and Thermodynamic Properties of Phases in the H2O–Gd(NO3)3 System

Phase Equilibria and Thermodynamic Properties of Phases in the H2O–Gd(NO3)3 System

Thermodynamic and kinetic parameters of iodine extraction from chloride aqueous solutions

Phase Equilibria and Thermodynamic Properties of Phases in the H2O–Gd(NO3)3 System

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