Abstract
The morphological evolution of micron-sized calcite crystals dissolved in static acidic solutions, with and without dissolved Pb2+ ions, was imaged using transmission X-ray microscopy (TXM). The area-normalized dissolution rates measured by TXM increased with time in both Pb-free and Pb-rich solutions but with distinct morphological evolution. Calcite reacted in Pb-free solutions exhibited rounding at corners and edges with faster dissolution at acute corners/edges than obtuse corners/edges. Numerical simulations indicate that this is controlled primarily by solution mass transport that is faster near the acute corners/edges. In comparison, dissolution of calcite in Pb-rich solutions was 50% slower than that in Pb-free solutions and exhibited less rounding at corners. Faces of the calcite rhombs exhibited increased surface roughness and the subsequent development of surface micropyramids that formed preferentially near the acute edges of the calcite rhombs. Spatially resolved dissolution rates reveal that pyramid formation is associated with reduced dissolution rates near the pyramid apex. The results demonstrate the role of impurity metal ions in controlling the dissolution rate and the associated complexities in the morphological evolution of dissolving mineral surfaces.
Original language | English |
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Pages (from-to) | 833-843 |
Number of pages | 11 |
Journal | ACS Earth and Space Chemistry |
Volume | 3 |
Issue number | 5 |
DOIs | |
State | Published - May 16 2019 |
Funding
This work was supported by U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division under Contract DE-AC02-06CH11357 to UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne is a U.S. Department of Energy Office of Science laboratory. CFD simulations used the advanced mesh relaxation techniques sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy. This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility, beamline 32-ID-C, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.
Keywords
- Pb
- X-ray nanotomography
- calcite
- competitive adsorption
- dissolution rate
- morphological instability
- numerical simulation
- transmission x-ray microscopy