Thermodynamics of vanadium–sulfur–water systems at 298 K

The thermodynamics of vanadium–sulfur–water systems are summarized in the form of potential–pH and activity–pH diagrams, calculated from published standard Gibbs energies of formation of the various species and phases considered. The potential–pH diagrams for V–S–H2O show that SO42− and HSO4− ions obviously enlarge the regions of stability of V3+, VO2+ and VO2+ ions, forming VSO4+, VOSO4(aq) and VO2SO4− at low pH range 0–5. Combining data in the existing literature with thermodynamic analysis, some examples of vanadium extraction and removal from vanadium stock solutions are discussed. Rational explanations are given for the behavior of vanadium.

Research Highlights
► The behaviors of both vanadium–water and vanadium–sulfur–water systems in the form of potential–pH and activity–pH diagrams are presented.
► SO42– and HSO4– ions enlarge the regions of stability of V3+, VO2+ and VO2+ ions, forming sulfate complexes.
► Some problems in vanadium extraction and removal from vanadium stock solutions are discussed with the help of thermodynamic diagrams.