Thermodynamic analysis for separation of vanadium and chromium in V(IV)-Cr(III)-H2O system
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract: To recycle vanadium and chromium from the V-Cr-bearing reducing slag, the thermodynamics of separating V(IV) and Cr(III) at 298 K was summarized in the form of potential-pH diagram and activity-pH diagram. The potential-pH diagrams of V-Mn-H2O and Cr-Mn-H2O systems show that the electrode potential of MnO2/Mn2+ is higher than that of VO2+/VO2+ but lower than that of Cr2O72-/Cr3+, which proves that it is feasible to selectively oxidize low valent vanadium using MnO2. The activity-pH diagrams of V(V)-H2O and Cr(III)-H2O systems show that the precipitation pH of V(V) is far lower than that of Cr(III), and therefore V(V) and Cr(III) can be separated through precipitation method. Based on the thermodynamic analysis, the flowsheet of recovery of vanadium and chromium from the V-Cr-bearing reducing slag is designed.
Key words: V-Cr-H2O system; vanadium; chromium; selective oxidation; selective precipitation