Variations in gangue minerals mineralogy, bulk and surface chemical structure and their solution interactions play a vital role in hydrometallurgical processing of mineral ores. The ores commonly processed for valuable mineral extraction are low grade, and mineralogically and chemically complex. Such properties present intractable challenges to process engineering during aqueous processing of mixed mineral ores. Through systematic studies involving single model phases performed under industrially relevant conditions, the complexity of the system is minimised and a greater fundamental understanding of the mineralogy and chemistry is obtained. Hence, a detailed characterisation of key properties involving principle mineral components (e.g. muscovite) of real ores, were established under well-defined processing conditions.
Bulk and surface characteristics of muscovite ((K_1.82,Na_0.13)(Al_3.64, Fe_0.29, Mg_0.16)[(Al_1.86, Si_6.14)O₂₀](OH)₄) leach residue, after isothermal batch leaching at 25 °C and 70 °C at pH 1, was probed as a function of leaching time. Resulting spectroscopic data highlighted key changes in bulk structure and surface chemistry; i.e. (i) an increase in octahedral, as compared with tetrahedral, coordinated aluminium, resulting from Al³⁺ leaching and re-adsorbing into the bulk or at the surface of the muscovite crystal (normally dictated by progressive net charge deficiency), and (ii) an increase in polymerisation at particle surfaces, resulting from back-precipitation of Si(IV) from solution, consequently changing the leaching mechanism of particles and rendering them virtually insoluble. These key findings are discussed in support of the possible mechanisms underpinning gelation and the fate of gangue clay minerals (e.g. muscovite, chlorite, smectite) during complex mineral ore processing.