Detecting Technetium in Groundwater

The Science

Technetium-99 (⁹⁹Tc) is a long-lived radionuclide byproduct of the nuclear fuel cycle, making it a major risk driver at former nuclear weapons production sites that requires onsite monitoring. A novel approach has been demonstrated that uses highly selective and sensitive platinum salt to detect and quantify the highly soluble pertechnetate (TcO₄^–) anion in groundwater.

The Impact

The new anion recognition approach has potential for the development of a field-deployable and highly accurate sensor for monitoring TcO₄^– in groundwater, river water, and watersheds. This work could have a broad impact on remediation efforts, paving the way for the development of similar salts for detection of other important environmental contaminants.

Summary

When exposed to moderately oxidizing conditions, ⁹⁹Tc is readily converted to pertechnetate (TcO₄^–), a highly soluble anion that can migrate into groundwater and the environment. Existing methods for onsite monitoring of TcO₄^– in groundwater require a complicated series of analytical steps due to the low selectivity and sensitivity of Tc. A team of scientists from Pacific Northwest National Laboratory (PNNL), Environmental Molecular Sciences Laboratory [EMSL; a U.S. Department of Energy (DOE) user facility], University of Cincinnati, and Florida State University searched for a suitable material for sensing TcO₄^– in water. The team evaluated simple salts of transition metal complexes that change in color and luminescence properties upon exposure to the Tc anion using the SPEX Fluorolog 2 fluorimeter at EMSL. They found one specific platinum salt that undergoes a dramatic color and brightness change upon exposure to TcO₄^–; the salt was highly sensitive and enables detection of TcO₄^– at levels well below the drinking water standard established by the U.S. Environmental Protection Agency. Modeling and simulation work using EMSL’s Cascade supercomputer enabled the team to determine that the high selectivity was due to the unique electronic structure of the platinum salt. Unlike currently available methods for TcO₄^– sensing, the new approach does not require separation, concentration, or other pretreatment steps. Thus, the rapid, sensitive, and accurate TcO₄^– sensing system is ideal for real-time deployment at contaminated sites. Future implementation of this type of ion recognition system has great potential for remediation efforts and could be essential in addressing a broad range of environmental and health concerns.

Principal Investigator(s)

Sayandev Chatterjee
Pacific Northwest National Laboratory
[email protected]

Tatiana Levitskaia
Pacific Northwest National Laboratory
[email protected]

Funding

This work was supported by DOE’s Office of Science, Office of Biological and Environmental Research and Office of Basic Energy Sciences, including support of EMSL; PNNL’s Laboratory-Directed Research and Development Program; National Science Foundation; and Office of Environmental Management Sciences Program.

References

Chatterjee, S., A. E. Norton, M. K. Edwards, J. M. Peterson, S. D. Taylor, S. A. Bryan, A. Andersen, N. Govind, T. E. Albrecht-Schmitt, W. B. Connick, and T. G. Levitskaia. 2015. “Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4–,” Inorganic Chemistry 54(20), 9914–23. DOI: 10.1021/acs.inorgchem.5b01664.