The solubility of barite and celestite in sodium sulfate: Evaluation of thermodynamic data

Abstract

The solubilities of barite [BaSO4(c)] and celestite [SrSO4(c)] in Na2SO4 were studied and found to be significantly lower than the experimental values reported in the literature. Our new solubility data are in excellent agreement with the predictions of ion interaction models, which have previously been parameterized primarily from solubility data obtained in chloride media. Our solubility data were analyzed both in terms of aqueous thermodynamic models that included ion association species and in terms of ion interaction models that did not require the explicit recognition of such species. In the case of SrSO4, although both ion association and ion interaction models can accurately model our solubility data, the ion interaction approach is preferred because it is easier to extend to higher concentrations. In the case of BaSO4, the aqueous ion interactions appear to be stronger than those for SrSO4, and so the explicit recognition of a BaSO4(aq) ion association species is preferred. The logarithms of the thermodynamic solubility products (log K sp ) for celestite and barite were −6.62±0.02 and −10.05±0.05, respectively. When the data were analyzed using models that include ion association species, the logarithms of the thermodynamic equilibrium constants for the SrSO4(aq) and BaSO4(aq) association reactions were 1.86±0.03 and 2.72±0.09, respectively.