PNNL

Abstract

Many aqueous electrolytes are only stable in the presence of another electrolyte, such as electrolytes that are only soluble in strong acid or base. An example is sodium aluminate [NaAl(OH)4], which is only stable in aqueous NaOH. This complicates developing thermodynamic parameters because it is difficult to separate the contribution of individual electrolytes in multicomponent solutions to measured bulk thermodynamic properties. The present study develops a method to determine the liquid phase parameters from solubility data for Zavitsas’ Hydration model – a model that incorporates hydration parameters into the activities of dissolved species. This study uses gibbsite [Al(OH)3] solubility data in aqueous NaOH solution to develop Zavitsas model parameters for NaAl(OH)4 simultaneously with the equilibrium constants. A good fit of the solubility data was found, showing that Zavitsas’ model is effective for this system