Computation of multi-component E-pH predominance diagrams

Pourbaix diagram and predominance area diagram are important thermodynamic stability diagrams. Computer programs have been developed to plot such diagrams. However, their application of E-pH Diagram are somewhat limited due to the differences between real conditions and those theoretically assumed. In this paper, a new algorithm is proposed on E-pH predominance diagrams. The equilibrium constant approach and activity term method are used to plot E-pH diagrams for Metal-H2O and Metal-Ligand-H2O systems based on the thermochemical database developed. A new approach, arithmetic-geometric method, is used to solve non-linear equations group, which proves to be efficient and easily convergent. The mathematical and computer algorithms are described, with the Pb-H2O, Cu-NH3-H2O and Cu-Cl-H2O systems as examples. More information on real hydrometallurgical processes can be obtained from these diagrams compared to conventional E-pH predominance diagrams.