A Pitzer Interaction Model for the NaNO₃–NaNO₂–NaOH–H₂O System from 0 to 100 °C

Abstract

The solubility relations and water activities in NaNO3, NaNO2, and NaOH solutions are used in many applications, including the management of alkaline high-level nuclear waste. Only limited water activity data is available at temperatures above ambient for NaNO3 and NaNO2 aqueous solutions, so water activity was measured by isopiestic methods at 50 and 100 °C in this study. The results are consistent with the limited experimental data previously available. These data are used to parameterize the Pitzer electrolyte solution model for these electrolytes and NaOH in water between 0 and 100 °C. Neutral ion pairs between Na+ and NO3 – as well as Na+ and NO2 – were required in order to fit the data adequately. Ternary Pitzer ion interaction parameters for the interactions between the electrolytes were also required and developed to model solubility in mixtures of the electrolytes. These results provide a strong foundation for modeling the effect of NaNO2, NaNO3, and NaOH on the solubility of other key electrolytes of interest to the management of high-level nuclear waste.

Recovery of metal oxoanions from basic solutions using cooperative sorption – Separation of Na2MoO4 and NaOH

“…The Pitzer parameters at 25 o C were taken from Kim and Frederick [18]. At 60 o C, parameters for NaOH have been reported by Reynolds et al [19] and the values for Na 2 MoO 4 were taken from Ref. [20].…”

A method to apply Zavitsas' aqueous electrolyte model to multicomponent solutions and its equivalence to Zdanovskii's rule

“…F I G U R E 1 Water activity of sodium nitrite solution as a function of concentration at 50 C. Data from Reynolds et al 24 Zavitsas has successfully fit his model to water activity data for aqueous NaNO 2 solution up to saturation at 25 C. 5 The present author has fit Zavitsas' model up to 17.74 molal NaNO 2 concentration at 100 C, and found an excellent fit. 16 The model may not fit osmotic coefficients for some electrolyte solutions at concentrations less than 0.1 molal, but the model appears to be a good choice for modelers who are interested in solutions with higher concentrations.…”

“…[18][19][20] The present author has used both models for radioactive waste at the Hanford Site in the United States. [21][22][23][24] These models and their cousins generally employ some form of the Debeye-Hṻckel equation in order to model electrolyte solution properties at low concentrations where the Debeye-Hṻckel equation applies. The Debeye-Hṻckel equation becomes increasingly less accurate as the concentration increases above 0.01 molal.…”

A Rothmund–Kornfeld model of Cs+–K+–Na+ exchange on spherical resorcinol-formaldehyde (sRF) resin in Hanford nuclear waste

“…Prediction of the liquid phase activity coefficients is difficult at these high concentrations [35]. Sodium forms ion-pairs with many of the anions in the waste [36,37] further complicating the calculation of the activity coefficients.…”

“…A Pitzer-based model to predict liquid-phase activity coefficients in Hanford waste is currently under development [37][38][39], though the current focus of the Hanford Pitzer model is on major components that affect the solubility of salts in the waste. The data is currently unavailable to build a model to calculate the activity coefficients of a trace species (Cs ? )…”