Replacement of Calcite (CaCO3) by Cerussite (PbCO3)
- Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Univ. of Delaware, Newark, DE (United States). Dept. of Geological Sciences
The mobility of toxic elements, such as lead (Pb) can be attenuated by adsorption, incorporation, and precipitation on carbonate minerals in subsurface environments. Here in this paper, we report a study of the bulk transformation of single-crystal calcite (CaCO3) into polycrystalline cerussite (PbCO3) through reaction with acidic Pb-bearing solutions. This reaction began with the growth of a cerussite shell on top of calcite surfaces followed by the replacement of the remaining calcite core. The external shape of the original calcite was preserved by a balance between calcite dissolution and cerussite growth controlled by adjusting the Pb2+ concentration and pH. The relation between the rounded calcite core and the surrounding lath-shaped cerussite aggregates was imaged by transmission X-ray microscopy, which revealed preferentially elongated cerussite crystals parallel to the surface and edge directions of calcite. The replacement reaction involved concurrent development ~100 nm wide pores parallel to calcite c-glide or (1$$\overline{20}$$) planes, which may have provided permeability for chemical exchange during the reaction. X-ray reflectivity measurements showed no clear epitaxial relation of cerussite to the calcite (104) surface. These results demonstrate Pb sequestration through mineral replacement reactions and the critical role of nanoporosity (3% by volume) on the solid phase transformation through a dissolution-recrystallization mechanism.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1368097
- Journal Information:
- Environmental Science and Technology, Vol. 50, Issue 23; ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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