Electrochemical and Kinetic Mechanism of Oxidizing Acid-Leaching Process of Niobium Tantalum Ore AITranslate

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Basic Information:

DOI：10.13373/j.cnki.cjrm.XY23030038

Chinese Library Classification Number:TF841.6

Citation Information:

In order to investigate the effects of oxidation conditions on the leaching rate of niobium tantalum ore，the cyclic voltammetry，Tafel polarization curve，impedance and open-circuit potential methods were used to study the effects of different oxidation potentials，different HF concentrations and different temperatures on the leaching rate of niobium tantalum ore. The cyclic voltammetry was used to investigate the oxidation reaction in the process of acid leaching of niobium tantalum ore. The cyclic voltammetry curve of niobium tantalum electrode had four oxidation peaks A₁，A₂，A₃ and A₄ of low valence Fe and Mn，and the oxidation peak potential values were -0.38，0.1，0.31 and 0.6 V，respectively. Among them，A₁ and A₂ were the oxidation peaks of MnO and Fe₃O₄ phases in niobium tantalum ore，corresponding to the oxidation of Mn²⁺ to Mn³⁺ and Fe²⁺ to Fe³⁺，respectively. A₃ and A₄ were the oxidation of （Fe，Mn）（Nb，Ta）₂O₆ mineral phase in niobium tantalum ore corresponding to the oxidation of Mn²⁺ to Mn³⁺ and Fe²⁺ to Fe³⁺ in （Fe，Mn）（Nb，Ta）₂O₆ mineral phase，respectively. The current density （J_coor） of Tafel polarization curve increased with the increase of HF concentration in the electrolyte，and reached the maximum value of 849.68 µA·cm⁻² at 10 mol·L⁻¹ HF. The anode slope decreased with the increase of HF concentration and then tended to be stable，indicating that the oxidation leaching rate of total mineral phase at the ore/liquid interface on the surface of niobium tantalum electrode increased with the increase of HF concentration and then tended to be stable after reaching the maximum value at 10 mol·L⁻¹ HF. At -0.38 and 0.1 V oxidation potential，AC impedance test of HF concentration on MnO and Fe₃O₄ mineral phases showed the charge transfer density （J_Rct） increased with increasing HF concentration. Mn charge transfer density J_Rct increased from 3.86 µA·cm⁻² of 4 mol·L⁻¹ HF to 68 µA·cm⁻² of 10 mol·L⁻¹ HF. Fe charge transfer density J_Rct increased from 1.11 µA·cm⁻² of 4 mol·L⁻¹ HF to 87.32 µA·cm⁻² of 10 mol·L⁻¹ HF. The leaching rates of Mn and Fe also accelerated with the increase of HF concentration in the electrolyte. Mn leaching rate reached the maximum of 29.4 mg·L⁻¹·h⁻¹ at 10 mol·L⁻¹ HF and Fe leaching rate reached the maximum of 5.5 mg·L⁻¹·h⁻¹ at 10 mol·L⁻¹ HF. The experimental results showed that the leaching rates of MnO and Fe₃O₄ mineral phase increased with the increase of HF concentration，and the leaching rates of Mn and Fe ions reached the maximum in 10 mol·L⁻¹ HF electrolyte. At 0.31 and 0.6 V oxidation potential，AC impedance test of HF concentration on （Fe，Mn）（Nb，Ta）₂O₆ mineral phase showed that Fe and Mn charge transfer density J_Rct increased with the increase of HF concentration in the electrolyte. Fe charge transfer density J_Rct increased from 1.94 µA·cm⁻² of 4 mol·L⁻¹ HF to 143.7 µA·cm⁻² of 11 mol·L⁻¹ HF. Mn charge transfer density J_Rct increased from 13.06 µA·cm⁻² of 4 mol·L⁻¹ HF to 168.4 µA·cm⁻² of 11 mol·L⁻¹ HF. The leaching rates of Fe and Mn element from niobium tantalum was also accelerated with the increase of HF concentration in the electrolyte. The leaching rate of Fe reached the maximum of 2.56 mg·L⁻¹·h⁻¹ at 11 mol·L⁻¹ HF and the leaching rate of Mn reached the maximum of 2.88 mg·L⁻¹·h⁻¹ at 11 mol·L⁻¹ HF. The experimental results showed that the leaching rate of （Fe，Mn）（Nb，Ta）₂O₆ mineral phase increases with the increase of HF concentration，and the leaching rate of Nb ion reached the maximum at 11 mol·L⁻¹ HF. Tafel results of niobium tantalum ore at different reaction temperatures showed that temperature had a significant effect on the oxidation leaching of niobium tantalum ore. With the increase of temperature，the oxidation leaching rate of niobium tantalum ore was accelerated，and the corrosion current density gradually increased. The corrosion current density tended to flatten out when it reached the maximum value of 959.20 µA·cm⁻² at 80 ℃. The dominant activation energy of Nb ion in the oxidation leaching stage was 3.018 kJ·mol⁻¹ based on Arrhenius formula. The results of AC impedance tests of （Fe，Mn）（Nb，Ta）₂O₆ mineral phase at different reaction temperatures and the determination of Nb ion leaching rate by inductively coupled plasma mass spectrometer （ICP） showed that with the increase of HF concentration，the oxidation current density also increased gradually，reaching the maximum 178.4 µA·cm⁻² and 192.5 µA·cm⁻² at 80 ℃. As determined by ICP，the oxidation leaching rate of Nb accelerated with the increase of temperature，reaching a maximum of 5.32 mg·L⁻¹·h⁻¹ at 80 ℃. The oxidation reaction rate of Nb ion was basically unchanged as the temperature continues to rise，which might be caused by the change of the double layer structure at the niobium tantalum/liquid interface with the increase of temperature. The results of impedance AC experiments at different temperatures showed that the current density increases with the increase of temperature，reaching the maximum values 192.5 µA·cm⁻² at 80 ℃.