Abstract:

The predominance diagram of dissolved species and a Pourbaix diagram of the V-H2O system with a high vanadium concentration were studied at 25 ℃ by a concentration comparison method. The concentration of dissolved species, borderlines for liquid phases or solid phases and borderlines between the solid and solid phase were calculated on the basis of thermodynamic analysis and electrochemical analysis with a total V concentration of cT(V)=1.0×10-3 mol·L-1. The predominance diagramof dissolved species and the Pourbaix diagramof the V-H2O system were then plotted. Comparisons made between predominance diagrams for cT(V)=1.0×10-3 mol·L-1 and cT(V)=1.0×10-5 mol·L-1 show that at a specific temperature and pressure the total concentration of vanadium has little effect on the stable predominance regions of the vanadium cation. These conditions also have a remarkable effect on the multi vanadium acid radical anion. A series of protonation and polymerization reactions may occur with the vanadate radical anion resulting in changes in the total concentration of vanadium and in acidity. A higher total concentration of vanadium and higher acidity result in a more stable multi-core vanadiumradical anion.

Key words: V-H2O system, Higher vanadiumconcentration, Pourbaix diagram, Predominance diagram, Concentration comparison method