Alteration of trioctahedral micas in the presence of inorganic and organic acids

The alteration of two trioctahedral micas, biotite and phlogopite, was investigated at the meso, micro, nanoscale using three complementary microscopy techniques to better understand mica surface reactivity. In situ ex experiments were performed monitor mineral interface during dissolution in acidic solutions (nitric oxalic acid, pH ∼ 1–2), over a temperature range 25–100°C. inorganic acid used as benchmark condition elucidate effect organic on behavior. observed topographical changes that arose revealed simultaneous occurrence different processes heterogeneously shaped surface: 1) retreat pre-existing newly formed steps (edge reactivity). case biotite, layer curling peeling-off occurred presence nitric whereas dendritic-shaped step edges resulted from acid; 2) nucleation etch pits formation channels (001) surface. Oxalic promoted growth such an extent they discernible each scale resolution investigated; 3) precipitation secondary phases. Overall, multi-scale approach offers new insights into behavior versus phlogopite provides enhances understanding has reactivity mica.