Chemical Sciences Division, Oak Ridge National Laboratory, MS 6110, Oak Ridge, Tennessee 37831-6110, United States
Physical Sciences Division. Pacific Northwest National Laboratory, Richland, Washington 99354, United States
The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States
Center for Neutron Research, National Institute of Standards and Technology, Stop 6102, Gaithersburg, Maryland 20889-6102, United States; Department of Materials Science and Eng. J. Clark School of Engineering, University of Maryland, College Park, Maryland 20742, United States
Center for Neutron Research, National Institute of Standards and Technology, Stop 6102, Gaithersburg, Maryland 20889-6102, United States
Argonne National Laboratory, 9700 S. Cass Avenue, Bldg. 433A, Argonne, Illinois 60439, United States
The U.S. government currently spends significant resources annually managing the legacies of the Cold War, including 300 million liters of highly radioactive wastes stored in hundreds of tanks at the Hanford Site (WA) and the Savannah River Site (SC). The materials in these tanks consist of highly radioactive slurries and sludges at very high pH and salt concentrations. The solid particles primarily consist of aluminum hydroxides and oxyhydroxides (gibbsite and boehmite), although many other materials are present. These form complex aggregates that dramatically affect the rheology of the solutions and, therefore, efforts to recover and treat these wastes. In this paper we have used a combination of transmission and cryo-transmission electron microscopy, dynamic light scattering, and X-ray and neutron small- and ultra-small angle scattering to study the aggregation in controlled environments of synthetic nano-boehmite particles at pH 9 (approximately the point of zero charge) and 12, and sodium-nitrate and calcium-nitrate concentrations up to 1 molal. While the initial particles form individual rhombohedral platelets, once placed in solution they quickly form well-bonded stacks, primary aggregates, up to ~ 150 nm long. These are more prevalent at pH=12. Addition of calcium-nitrate or sodium-nitrate has a similar effect as lowering pH, but approximately one hundred times less calcium than sodium is needed to observe this effect. These aggregates have fractal dimension between 2.5 and 2.6 that are relatively unaffected by salt concentration for calcium-nitrate at high pH. Larger aggregates (> ~ 400 nm) are also formed, but their size distributions are discrete rather than continuous. The fractal dimensions of these aggregates are strongly pH dependent but only become dependent on solute at high salt concentrations.
Anovitz, L. M., et al. "Effects of Ionic Strength, Salt, and pH on Aggregation of Boehmite Nanocrystals: Tumbler Small-Angle Neutron and X-ray Scattering and Imaging Analysis." Langmuir, vol. 34, no. 51, Oct. 2018. https://doi.org/10.1021/acs.langmuir.8b00865
Anovitz, L. M., Zhang, X., Soltis, J., Nakouzi, E., Krzysko, A. J., Chun, J., Schenter, G. K., Graham, T. R., Rosso, K. M., De Yoreo, J. J., Stack, A. G., Bleuel, M., Gagnon, C., Mildner, D. F. R., Ilavsky, J., & Kuzmenko, I. (2018). Effects of Ionic Strength, Salt, and pH on Aggregation of Boehmite Nanocrystals: Tumbler Small-Angle Neutron and X-ray Scattering and Imaging Analysis. Langmuir, 34(51). https://doi.org/10.1021/acs.langmuir.8b00865
Anovitz, L. M., Zhang, X., Soltis, J., et al., "Effects of Ionic Strength, Salt, and pH on Aggregation of Boehmite Nanocrystals: Tumbler Small-Angle Neutron and X-ray Scattering and Imaging Analysis," Langmuir 34, no. 51 (2018), https://doi.org/10.1021/acs.langmuir.8b00865
@article{osti_1494398,
author = {Anovitz, L. M. and Zhang, X. and Soltis, J. and Nakouzi, E. and Krzysko, A. J. and Chun, J. and Schenter, G. K. and Graham, T. R. and Rosso, K. M. and De Yoreo, J. J. and others},
title = {Effects of Ionic Strength, Salt, and pH on Aggregation of Boehmite Nanocrystals: Tumbler Small-Angle Neutron and X-ray Scattering and Imaging Analysis},
annote = {The U.S. government currently spends significant resources annually managing the legacies of the Cold War, including 300 million liters of highly radioactive wastes stored in hundreds of tanks at the Hanford Site (WA) and the Savannah River Site (SC). The materials in these tanks consist of highly radioactive slurries and sludges at very high pH and salt concentrations. The solid particles primarily consist of aluminum hydroxides and oxyhydroxides (gibbsite and boehmite), although many other materials are present. These form complex aggregates that dramatically affect the rheology of the solutions and, therefore, efforts to recover and treat these wastes. In this paper we have used a combination of transmission and cryo-transmission electron microscopy, dynamic light scattering, and X-ray and neutron small- and ultra-small angle scattering to study the aggregation in controlled environments of synthetic nano-boehmite particles at pH 9 (approximately the point of zero charge) and 12, and sodium-nitrate and calcium-nitrate concentrations up to 1 molal. While the initial particles form individual rhombohedral platelets, once placed in solution they quickly form well-bonded stacks, primary aggregates, up to ~ 150 nm long. These are more prevalent at pH=12. Addition of calcium-nitrate or sodium-nitrate has a similar effect as lowering pH, but approximately one hundred times less calcium than sodium is needed to observe this effect. These aggregates have fractal dimension between 2.5 and 2.6 that are relatively unaffected by salt concentration for calcium-nitrate at high pH. Larger aggregates (> ~ 400 nm) are also formed, but their size distributions are discrete rather than continuous. The fractal dimensions of these aggregates are strongly pH dependent but only become dependent on solute at high salt concentrations.},
doi = {10.1021/acs.langmuir.8b00865},
url = {https://www.osti.gov/biblio/1494398},
journal = {Langmuir},
issn = {ISSN 0743-7463},
number = {51},
volume = {34},
place = {United States},
publisher = {American Chemical Society},
year = {2018},
month = {10}}
Argonne National Laboratory (ANL), Argonne, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Interfacial Dynamics in Radioactive Environments and Materials (IDREAM); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)