Modeling chemical and phase equilibria in geochemical systems using a speciation-based model

Abstract

A comprehensive thermodynamic model has been applied to calculating phase equilibria, speciation, and other thermodynamic properties of systems that are of geochemical importance. The analyzed systems are relevant to the mineralization of Pb, Ni, Cu, Zn, and Fe. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 °C and for concentrations ranging from infinite dilution to the fused salt limit. The accuracy of the model has been demonstrated by calculating solubilities in multicomponent solutions and predicting the effects of chemical speciation, pH, temperature, CO 2 partial pressure, and concentrations of acids, bases, and selected salts on the formation of various solid phases.