Interactions of aqueous metal ions with mineral surfaces play a critical role in understanding the mobility of metals in subsurface environments, templating growth of secondary mineral phases, and top-down design of complex surface structures. Here, we showed an example of calcite interactions with Pb2+ and Fe2+ ions respectively during the mineral dissolution reaction. In Pb-calcite interactions, calcite exhibits non-classical surface features characterized as micro pyramids developed spontaneously in acidic Pb-bearing solutions. Subsequent pseudomorphic growth of a cerussite (PbCO3) phase was observed, where nucleation occurred entirely within a pore space created by dissolution at the calcite/substrate interface. Cerussite was separated from the calcite by pores of less than 200 nm, consistent with an interface-coupled dissolution-precipitation mechanism. In the study of Fe-calcite interactions, formation of iron oxyhydroxide layers having distinct morphologies was observed during the dissolution of calcite in acidic Fe(II)-rich solutions. A pseudomorphic lepidocrocite (γ-FeOOH) shell together with multiple iron oxyhydroxide layers encapsulated within the shell was imaged by optical and transmission X-ray microscopies. Subsequent detachment of the lepidocrocite film from the dissolving calcite surface yielded a freestanding pseudomorphic iron oxyhydroxide micro box. The results highlighted the different nature of metal ions on influencing mineral dissolution and formation of complex structures at the mineral-water interface.

Imaging calcite dissolution in the presence of metal ions by transmission X-ray microscopy

256th National Meeting (2018)

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