Salt roasting-water leaching of complex vanadium ores: a thermodynamic approach

Plots of free energy of reactions versus temperature for the interaction of the simple oxides V2O5, SiO2, Al2 O3, Fe2O3 and TiO2 with NaCl or Na2Co3 were established for different oxide and sodium salt activities, as well as for different partial pressure of O2, H2O, Cl2 and HCl to predict the formation of sodium salts during the salt roasting of vanadium ores. Experimental evidence showed that, despite its lower selectivity, the use of sodium carbonate promotes higher vanadium recoveries as sodium vanadates. Eh-pH diagrams of the V-Na-H2O system indicated the feasibility of water leaching of sodium vanadate at 298K for different molar activities of vanadium and sodium.