Potassium recovery from Brazilian glauconitic siltstone by hydrothermal treatments

Abstract Silicate rock Verdete, collected in the central region of Minas Gerais state (Brazil) and composed mostly of micas (glauconite and muscovite) and tectosilicates (K-feldspar and quartz), was hydrothermally treated with several reactants in order to release and recover potassium. The hydrothermal products were characterized by flame photometry, XRD, XRF, SEM and EDS. Treatment with sulfuric acid was effective to break the crystal lattice of micas before 1 h of reaction and recovered 24% of potassium in the form of sulfates. The K-feldspar appears to have remained intact during the proce...