The Solubilities of Gibbsite and Bayerite Below 100 °C in Near Neutral to Basic Solutions

The purpose of this paper is to present a new set of experimental results on the solubility of crystalline bayerite and gibbsite in caustic NaNO3 media (I m = 0.1–5 mol·kg−1) from 303 to 363 K, reflecting conditions in the high-level nuclear waste repository at the Hanford site in the USA. The resulting molal solubility constants, K m,s,4, were combined with some previous literature values and modeled using the SIT and Pitzer ion-interaction models in order to provide a coherent internally-consistent set of data quantifying the thermodynamic dissolution behavior of these aluminum phases. The two models led to similar thermodynamic quantities compatible with those from previous studies for bayerite and gibbsite, and in both cases the differences in the ion-interaction parameters could be taken as being temperature independent.