Evolution of Hematite Surface Microtopography Upon Dissolution by Simple Organic Acids
Clays and clay minerals
The surface microtopography of hematite over the course of dissolution in oxalic and citric acids was examined by in-situ and ex-situ atomic-force microscopy, ln-situ imaging of the basal-plane surface of a centimeter-scale natural hematite sample immersed in 2 mM citric acid demonstrated that the basal-plane surface was relatively unreactive; rather, dissolution occurred along step edges and via etch-pit formation. Ex-situ imaging of synthetic hematite particles following batch dissolution in
... tch dissolution in 1 mM oxalic acid showed similar dissolution features on basal-plane surfaces; in addition, etching along particle edges was apparent. The presence of etch features is consistent with a surface-controlled dissolution reaction. The results are in agreement with previous investigations suggesting that the basal-plane surface is relatively unreactive with respect to ligand exchange. Both in-situ and ex-situ imaging of particle surfaces can provide valuable information on the roles of surface structures and microtopographic features in mineral dissolution.