03/25/2013

Impurities in Natural Minerals Can Affect Uranium Mobility

Summary

Uranium groundwater contamination resulted from mining for use as an energy source, as well as from past enrichment and weapons production activities at U.S. Department of Energy (DOE) sites. Understanding the impact of uranium contamination on water sources and developing appropriate remediation strategies are needed both to protect public safety and to continue the use of uranium in a balanced energy portfolio. Groundwater travels underground through a complex mixture of soils and sediments. A magnetic iron oxide mineral, magnetite, is commonly found in these sediments. Magnetite can significantly slow uranium migration, acting like a “rechargeable battery” for continued uranium removal from groundwater. It performs this task by sequestering the uranium as nanoparticles of uranium dioxide within underground sediments. Researchers at Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory now have found that titanium, a common impurity in these natural magnetic iron minerals, obstructs the formation of the uraninite nanoparticles, resulting in the formation of novel molecular-sized uranium-titanium structures. This previously unknown association of uranium with titanium affects uranium’s mobility in subsurface groundwater. Incorporating this knowledge into ongoing modeling efforts will improve scientists’ ability to predict future migration of subsurface contaminant plumes and provide detailed information needed for long-term stewardship of DOE legacy sites. The researchers used ANL’s Advanced Photon Source to study how uranium interacts with magnetite within the complex subsurface chemical environment.

References

Latta, D. E., C. I. Pearce, K. M. Rosso , K. M. Kemner, and M. I. Boyanov. 2013. “Reaction of U^VI with Titanium-Substituted Magnetite: Influence of Ti on U^IV Speciation,” Environmental Science and Technology 47(9), 421–30. DOI: 10.1021/es303383n.