Abstract:Aiming at the separation of vanadium over iron from acidic leaching solution, the thermodynamic equilibrium diagrams for distribution of species at different pH values and different concentrations of vanadium, iron and sulfur with the systems of V(Ⅴ)-Fe(Ⅲ)-S(Ⅵ)-H₂O at 298 K were drawn. The variation regularities were also analyzed. Based on the thermodynamic analysis, the corresponding separation methods of vanadium/iron were put forward. The results show that Fe³⁺and cations are predominant specials of iron and vanadium in strong acidic solution (-1＜pH＜0.5), respectively. When 0.5＜pH, due to the coordination of sulfate，Fe³⁺transforms to and then progressively, alongside this progressively polymerized to various polyanions. pH_50% is defined as the pH value when target metal anions occupy 50% mole fraction of total. It can be seen that the more vanadium in solution the lesser the pH_50%,V,the more iron the larger the pH_{50%, Fe}, the more sulfur in solution the smaller the pH_{50%, Fe}. In the pH range of pH_{50%, V}-pH_{50%, Fe}, in view of the difference of ionic electrical properties between vanadium and iron, the effective separation of vanadium over iron can be achieved by ether choosing alkaline extractant or ion exchange resin to preferentially adsorb vanadium polyanions oracid extractant or ion exchange resin to preferentially adsorb iron.

Key words: V(Ⅴ)-Fe(Ⅲ)-S(Ⅵ)-H₂O system; thermodynamic; pH_50%; solvent extraction; ions exchange