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Title: In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite

Abstract

Aluminum hydroxide (Al(OH) 3, gibbsite) dissolution and precipitation processes in alkaline environments play a commanding role in aluminum refining and nuclear waste processing, yet mechanistic aspects underlying sluggish kinetics during crystallization have remained obscured due to a lack of in situ probes capable of isolating incipient ion pairs. At a molecular level Al is cycling between tetrahedral (T d) coordination in solution to octahedral (O h) in the solid. We explored dissolution of Al(OH) 3 that was used to produce variably saturated aluminate (Al(OH) 4 )-containing solutions under alkaline conditions (pH >13) with in situ 27Al magic angle spinning (MAS)–nuclear magnetic resonance (NMR) spectroscopy, and interrogated the results with ab initio molecular dynamics (AIMD) simulations complemented with chemical shift calculations. The collective results highlight the overall stability of the solvation structure for T d Al in the Al(OH) 4 oxyanion as a function of both temperature and Al concentration. The observed chemical shift did not change significantly even when the Al concentration in solution became supersaturated upon cooling and limited precipitation of the octahedral Al(OH) 3 phase occurred. However, subtle changes in Al(OH) 4 speciation correlated with the dissolution/precipitation reaction were found. AIMD-informed chemical shift calculations indicate thatmore » measurable perturbations should begin when the Al(OH) 4 ···Na + distance is less than 6 Å, increasing dramatically at shorter distances, coinciding with appreciable changes to the electrostatic interaction and reorganization of the Al(OH) 4 solvation shell. The integrated findings thus suggest that, under conditions incipient to and concurrent with gibbsite crystallization, nominally expected contact ion pairs are insignificant and instead medium-range (4–6 Å) solvent-separated Al(OH) 4 ···Na + pairs predominate. Moreover, the fact that these medium-range interactions bear directly on resulting gibbsite characteristics was demonstrated by detailed microscopic and X-ray diffraction analysis and by progressive changes in the fwhm of the O h resonance, as measured by in situ NMR. Sluggish gibbsite crystallization may arise from the activation energy associated with disrupting this robust medium-range ion pair interaction.« less

Authors:
 [1];  [2];  [3]; ORCiD logo [2]; ORCiD logo [4]; ORCiD logo [2];  [5]; ORCiD logo [5]; ORCiD logo [5];  [2];  [6];  [2]; ORCiD logo [3];  [7];  [7]; ORCiD logo [2]; ORCiD logo [2]
  1. Washington State Univ., Pullman, WA (United States). Voiland School of Chemical and Biological Engineering
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Washington State Univ., Pullman, WA (United States). Dept. of Chemistry
  4. Washington State Univ., Pullman, WA (United States). Voiland School of Chemical and Biological Engineering; Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. TradeWind Services LLC, Richland, WA (United States)
  7. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Energy Frontier Research Centers (EFRC) (United States). Interfacial Dynamics in Radioactive Environments and Materials (IDREAM); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1482434
Alternate Identifier(s):
OSTI ID: 1596361
Grant/Contract Number:  
AC05-00OR22725; AC06-76RLO1830; AC06-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 57; Journal Issue: 19; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES

Citation Formats

Graham, Trent R., Dembowski, Mateusz, Martinez-Baez, Ernesto, Zhang, Xin, Jaegers, Nicholas R., Hu, Jianzhi, Gruszkiewicz, Miroslaw S., Wang, Hsiu-Wen, Stack, Andrew G., Bowden, Mark E., Delegard, Calvin H., Schenter, Gregory K., Clark, Aurora E., Clark, Sue B., Felmy, Andrew R., Rosso, Kevin M., and Pearce, Carolyn I. In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite. United States: N. p., 2018. Web. doi:10.1021/acs.inorgchem.8b00617.
Graham, Trent R., Dembowski, Mateusz, Martinez-Baez, Ernesto, Zhang, Xin, Jaegers, Nicholas R., Hu, Jianzhi, Gruszkiewicz, Miroslaw S., Wang, Hsiu-Wen, Stack, Andrew G., Bowden, Mark E., Delegard, Calvin H., Schenter, Gregory K., Clark, Aurora E., Clark, Sue B., Felmy, Andrew R., Rosso, Kevin M., & Pearce, Carolyn I. In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite. United States. doi:10.1021/acs.inorgchem.8b00617.
Graham, Trent R., Dembowski, Mateusz, Martinez-Baez, Ernesto, Zhang, Xin, Jaegers, Nicholas R., Hu, Jianzhi, Gruszkiewicz, Miroslaw S., Wang, Hsiu-Wen, Stack, Andrew G., Bowden, Mark E., Delegard, Calvin H., Schenter, Gregory K., Clark, Aurora E., Clark, Sue B., Felmy, Andrew R., Rosso, Kevin M., and Pearce, Carolyn I. Mon . "In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite". United States. doi:10.1021/acs.inorgchem.8b00617. https://www.osti.gov/servlets/purl/1482434.
@article{osti_1482434,
title = {In Situ 27Al NMR Spectroscopy of Aluminate in Sodium Hydroxide Solutions above and below Saturation with Respect to Gibbsite},
author = {Graham, Trent R. and Dembowski, Mateusz and Martinez-Baez, Ernesto and Zhang, Xin and Jaegers, Nicholas R. and Hu, Jianzhi and Gruszkiewicz, Miroslaw S. and Wang, Hsiu-Wen and Stack, Andrew G. and Bowden, Mark E. and Delegard, Calvin H. and Schenter, Gregory K. and Clark, Aurora E. and Clark, Sue B. and Felmy, Andrew R. and Rosso, Kevin M. and Pearce, Carolyn I.},
abstractNote = {Aluminum hydroxide (Al(OH)3, gibbsite) dissolution and precipitation processes in alkaline environments play a commanding role in aluminum refining and nuclear waste processing, yet mechanistic aspects underlying sluggish kinetics during crystallization have remained obscured due to a lack of in situ probes capable of isolating incipient ion pairs. At a molecular level Al is cycling between tetrahedral (Td) coordination in solution to octahedral (Oh) in the solid. We explored dissolution of Al(OH)3 that was used to produce variably saturated aluminate (Al(OH)4–)-containing solutions under alkaline conditions (pH >13) with in situ 27Al magic angle spinning (MAS)–nuclear magnetic resonance (NMR) spectroscopy, and interrogated the results with ab initio molecular dynamics (AIMD) simulations complemented with chemical shift calculations. The collective results highlight the overall stability of the solvation structure for Td Al in the Al(OH)4– oxyanion as a function of both temperature and Al concentration. The observed chemical shift did not change significantly even when the Al concentration in solution became supersaturated upon cooling and limited precipitation of the octahedral Al(OH)3 phase occurred. However, subtle changes in Al(OH)4– speciation correlated with the dissolution/precipitation reaction were found. AIMD-informed chemical shift calculations indicate that measurable perturbations should begin when the Al(OH)4–···Na+ distance is less than 6 Å, increasing dramatically at shorter distances, coinciding with appreciable changes to the electrostatic interaction and reorganization of the Al(OH)4– solvation shell. The integrated findings thus suggest that, under conditions incipient to and concurrent with gibbsite crystallization, nominally expected contact ion pairs are insignificant and instead medium-range (4–6 Å) solvent-separated Al(OH)4–···Na+ pairs predominate. Moreover, the fact that these medium-range interactions bear directly on resulting gibbsite characteristics was demonstrated by detailed microscopic and X-ray diffraction analysis and by progressive changes in the fwhm of the Oh resonance, as measured by in situ NMR. Sluggish gibbsite crystallization may arise from the activation energy associated with disrupting this robust medium-range ion pair interaction.},
doi = {10.1021/acs.inorgchem.8b00617},
journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 19,
volume = 57,
place = {United States},
year = {2018},
month = {7}
}

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Works referencing / citing this record:

Inference of principal species in caustic aluminate solutions through solid-state spectroscopic characterization
journal, January 2020

  • Dembowski, Mateusz; Prange, Micah P.; Pouvreau, Maxime
  • Dalton Transactions, Vol. 49, Issue 18
  • DOI: 10.1039/d0dt00229a