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Abstract  

Enthalpies of solution and dilution of aqueous solutions of sodium diclofenac salt were measured by isoperibolic calorimeter at 293.15, 298.15, 303.15, 308.15 and 318.15 K. The concentration of the electrolyte was restricted to solubility salt at various temperatures and did not exceed 0.035–0.057 mol kg−1 values depending on the studied temperature. The virial coefficients were derived from Pitzer’s model and the excess thermodynamic functions of both the solution and the components of the solution were calculated. The analysis of thermodynamic characteristics of the solution from concentration and temperatures was carried out and discussed.

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_DC) presented in Fig. 1 . The aim of this study was: to derive the experimental values of the solution enthalpies for K_DC in water at wide concentration and temperature intervals; to calculate the virial coefficients within Pitzer's model and determine the

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Borkowski, R. Moore, M. Bronikowski, Jianfeng Chen, O. Pokrovsky, Yuanxian Xia, and G. Choppin

Abstract  

A geochemical model describing the solubility of actinides in underground water at the Waste Isolation Pilot Plant (WIPP) Project is under development. The database for this model consists of standard chemical potentials and Pitzer model parameters for hundreds of species that may be present in the WIPP disposal room. Organic ligands used in separation and decontamination processes may be present in the nuclear wastes placed in the WIPP site and could have a significant impact on mobile actinide concentrations. In this work the 1 and 2 stability constants of NpO2 +, UO2 2+, Am3+ and Th4+ with the oxalate anion have been measured in 0.3–5.0M NaCl media at 25 °C by a solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO2 +<Am3+<UO2 2+<Th4+, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction model was used to model the data. Because the data were collected mainly in the high ionic strength region, values of (1) were estimated from these plus literature values. The Pitzer model gives a good representation of the data using three interaction parameters (0), (1), and c.

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Abstract  

Results of calorimetric determination of integral enthalpies of solution of some hydrates (monohydrates and heptahydrates) of 3d transition metal sulphates such as FeSO4, NiSO4 and MnSO4 in three-component systems at sulphuric acid concentrations up to 2M are reported. Measured values of integral enthalpies of solution are the basis for calculation of activity coefficient temperature dependences according to Pitzer's model.

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