Abstract
Radioactive iodine-129 (129I) and technetium-99 (99Tc) pose a risk to groundwater due to their long half-lives, toxicity, and high environmental mobility. Based on literature reviewed in Moore et al. (2019) and Pearce et al. (2019), natural and engineered materials, including iron oxides, low-solubility sulfides, tin-based materials, bismuth-based materials, organoclays, and metal organic frameworks, were tested for potential use as a deployed technology for the treatment of 129I and 99Tc to reduce environmental mobility. Materials were evaluated with metrics including capacity for IO3 − and TcO4 − uptake, selectivity and long-term immobilization potential. Batch testing was used to determine IO3 − and TcO4 − sorption under aerobic conditions for each material in synthetic groundwater at different solution to solid ratios. Material association with IO3 − and TcO4 − was spatially resolved using scanning electron microscopy and X-ray microprobe mapping. The potential for redox reactions was assessed using X-ray absorption near edge structure spectroscopy. Of the materials tested, bismuth oxy(hydroxide) and ferrihydrite performed the best for IO3 −. The commercial Purolite A530E anion-exchange resin outperformed all materials in its sorption capacity for TcO4 −. Tin-based materials had high capacity for TcO4 −, but immobilized TcO4 − via reductive precipitation. Bismuth-based materials had high capacity for TcO4 −, though slightly lower than the tin-based materials, but did not immobilize TcO4 − by a redox-drive process, mitigating potential negative re-oxidation effects over longer time periods under oxic conditions. Cationic metal organic frameworks and polymer networks had high Tc removal capacity, with TcO4 − trapped within the framework of the sorbent material. Although organoclays did not have the highest capacity for IO3 − and TcO4 − removal in batch experiments, they are available commercially in large quantities, are relatively low cost and have low environmental impact, so were investigated in column experiments, demonstrating scale-up and removal of IO3 − and TcO4 − via sorption, and reductive immobilization with iron- and sulfur-based species.
| Original language | English |
|---|---|
| Article number | 136167 |
| Journal | Science of the Total Environment |
| Volume | 716 |
| DOIs | |
| State | Published - May 10 2020 |
Funding
This document was prepared under the Deep Vadose Zone – Applied Field Research Initiative at Pacific Northwest National Laboratory. SEM measurements were performed in the Environmental Molecular Science Laboratory, a national user facility supported by the DOE Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Use of the Advanced Photon Source, an Office of Science User Facility operated by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. The authors thank Grant Scheve (Rogue BC, Biomass One) for providing the biochar sample. The authors acknowledge Steven Baum and Ian Leavy for ICP-MS measurements, Mark Bowden for assistance with XRD interpretation and Tom Resch for producing the thin sections for SEM analysis. Chris Johnson, David MacPherson and Michael Truex are acknowledged for their careful review, and Jessica Zuleta for technical editing. The Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the DOE under Contract DE-AC05-76RL01830. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. Appendix A This document was prepared under the Deep Vadose Zone ? Applied Field Research Initiative at Pacific Northwest National Laboratory. SEM measurements were performed in the Environmental Molecular Science Laboratory, a national user facility supported by the DOE Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Use of the Advanced Photon Source, an Office of Science User Facility operated by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. The authors thank Grant Scheve (Rogue BC, Biomass One) for providing the biochar sample. The authors acknowledge Steven Baum and Ian Leavy for ICP-MS measurements, Mark Bowden for assistance with XRD interpretation and Tom Resch for producing the thin sections for SEM analysis. Chris Johnson, David MacPherson and Michael Truex are acknowledged for their careful review, and Jessica Zuleta for technical editing. The Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the DOE under Contract DE-AC05-76RL01830. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.
Keywords
- Bismuth-based materials
- Iodate
- Iron oxides
- Layered double hydroxides
- Metal organic frameworks
- Pertechnetate