Chromate Effect on Iodate Incorporation into Calcite
- BATTELLE (PACIFIC NW LAB)
Incorporation of iodate into calcite (CaCO3) may be used as an in situ treatment strategy for radioiodine in contaminated soils and groundwater, but the presence of other contaminants can inhibit its efficiency. To this end, the potential for chromate to interfere with iodate incorporation into CaCO3 was investigated as an example of how co-located contaminants can impact in situ remediation efficacy. Here, batch precipitation experiments were periodically sub-sampled over 21 days to determine the kinetic effects of chromate on iodate removal and incorporation into calcite. From these experiments, a decrease in iodate removal from >60% to <40% was observed upon chromate addition (1 - 100 ppm chromate) and =11% of chromate was removed with a minor dependence on the initial chromate concentration. Analysis of the solid phase using extended X-ray absorption fine structure (EXAFS) spectroscopy informed by ab initio molecular dynamics simulations revealed that the iodate incorporation mode remains unchanged by the presence of chromate. Iodate readily substitutes for carbonate (CO32-) and the calcite structure is charge balanced primarily by substituting H+ for Ca2+. Furthermore, chromate incorporated as a nearest neighbor to iodate did not contribute to the EXAFS fit, therefore, iodate and chromate clustering is unlikely when co-incorporated into calcite.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1571648
- Report Number(s):
- PNNL-SA-141592
- Journal Information:
- ACS Earth and Space Chemistry, Journal Name: ACS Earth and Space Chemistry Journal Issue: 8 Vol. 3
- Country of Publication:
- United States
- Language:
- English
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