Abstract
Iron impurity tends to precipitate and reduces vanadium product purity during vanadium extraction from black shale. Oxalic acid is an eco-friendly leachant which can enhance vanadium selective separation from iron impurity. In this paper, the separation mechanism was systematically investigated. The mineral phases transformations and thermodynamics analysis indicate that the FeS2 in black shale can react with H2C2O4, HC2O4-, C2O42- and O2, as a result, the pyrite surface was coated by ferrous oxalate passivation layer, which can depress pyrite dissolution reaction. Meanwhile, the density functional theory (DFT) calculations show that the H2C2O4, HC2O4- and C2O42- can reconstruct FeS2 (100) surface by adsorption, and the adsorption energy can be as low as −3.73 eV for C2O42- adsorption configuration. The electrons in Fe atoms were transferred to O atoms and the stable Fe-O bands together with closed seven/eight-membered rings structures were formed as passivation layer, which can weaken and reduce Fe atoms reactive activation for the FeS2 during oxalic acid leaching. This study reveals vanadium separation from iron due to pyrite passivation in presence of oxalic acid at an atomic level.
Published Version
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