Removal Process of Structural Oxygen from Tetrahedrons in Muscovite during Acid Leaching of Vanadium-Bearing Shale

Process mineralogy shows that most vanadium in mica-type black shale exists in the octahedral sites of muscovite. The extraction of vanadium mainly occurs in the acid leaching process with participation of H ions. In this work, we firstly analyzed the dissolution rules of elements in acid leaching of muscovite, then adopted the density functional theory (DFT) calculation to accurately visualize the primary process of the surface corrosion of muscovite by H ions. The experimental results show that K releases the fastest and the release of Al is consistent with K. The simulation results find that the H preferentially shifts to the unsaturated structured O of the tetrahedron to form a strong 001 surface hydroxyl after replacing K, as well as relaxing the near Al(Si)-O bonds for the further removal of structural oxygen. Then, the 001 surface hydroxyls more likely participate in the dehydroxylation reaction through the reverse-path mechanism to remove the structural oxygen and break the hexagonal rings of the tetrahedral sheets. Remarkably, the formation and removal of structural water are overall endoergic, meaning that the disintegration of muscovite requires a sustained supply of heat. Further, the octahedral sheets where vanadium exists can be exposed to the acid environment for overall destruction. This detailed atomic migration process in acid leaching of black shale is visualized, which not only illuminates the reaction mechanism of H ions with the muscovite, but also provides guidance for vanadium extraction from black shale and a new concept for the destruction of other minerals.