The Mechanism of Oxidation Leaching (Fe,Mn)(Nb,Ta)₂O₆ in HF Medium

According to the mineral phase composition and refractory leaching characteristics of Columbo-tantalite, the main goal of the paper was to investigate mechanism of the oxidation leaching Columbo-tantalite in hydrofluoric acid medium. The oxidation behavior of divalent Fe and divalent Mn in (Fe,Mn)(Nb,Ta)₂O₆ mineral was determined by electrochemical method. Cyclic voltammetry, Tafel polarization curve, combining with AC impedance, open circuit potential, and other methods were used to study the electrochemical oxidation process and leaching rate of Columbo-tantalite in hydrofluoric acid medium with the concentration of 11 mol/L HF. The result showed that the oxidation peak of 0.3 and 0.6V matched the oxidation of divalent Fe and divalent Mn in (Fe,Mn)(Nb,Ta)₂O₆ mineral by the method of cyclic voltammetry curve combined with the charge transfer number. The results also showed that the oxidation leaching rate of Nb and Mn increased gradually with the increase of applied oxidation voltage. The maximum oxidation leaching rate was at 0.6 V with current density of 173.1 µA/cm². Oxidation voltage of 0.6 V corresponds to the oxidation of 25 pct H₂O₂, and the Nb leaching degree of Columbo-tantalite could reach 95.54 pct at 80 °C.