Structure and reactivity of sodium aluminate complexes in alkaline solutions

Emily T. Nienhuis; Maxime Pouvreau; Trent R. Graham; Micah P. Prange; Katharine Page; John S. Loring; Andrew G. Stack; Aurora E. Clark; Gregory K. Schenter; Kevin M. Rosso; Carolyn I. Pearce; Hsiu Wen Wang

doi:10.1016/j.molliq.2022.120379

Structure and reactivity of sodium aluminate complexes in alkaline solutions

Emily T. Nienhuis, Maxime Pouvreau, Trent R. Graham, Micah P. Prange, Katharine Page, John S. Loring, Andrew G. Stack, Aurora E. Clark, Gregory K. Schenter, Kevin M. Rosso, Carolyn I. Pearce, Hsiu Wen Wang

Geochemistry & Interfacial Science

Research output: Contribution to journal › Article › peer-review

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Abstract

The underlying mechanism by which tetrahedrally-coordinated aluminate solution species react to precipitate octahedrally-coordinated Al³⁺ in gibbsite is unknown. Sodium aluminate solutions provide the opportunity to investigate the role of ion speciation and local structure in the reaction, as the solution metastability can be controlled by varying ratio of excess NaOD to Al³⁺. Here, capitalizing on this tunable precipitation behavior, aluminate speciation was investigated through a combination of Raman, infrared, and NMR spectroscopies, together with geometrical fitting of neutron and X-ray radial distribution functions. These techniques reveal a mixture of monomeric Al(OD)₄⁻ and dimeric Al₂O(OD)₆²⁻ in all compositions, but solutions avoiding precipitation for extended timescales (i.e. months to years) show an increased dimeric Al₂O(OD)₆²⁻ population formed at the expense of the Al(OD)₄⁻ monomer. Conversion between these species, as well the potential for further oligomerization and formation of larger pre-nucleation species is driven by the hydrogen/deuterium bonding (H/D-bonding) and proton/deuteron transfer reactions. Changes within the local environment around the aluminate anions, including solvation and the presence of solvent-shared ion pairs or contact ion pairs, will consequently govern the reactivity of these aluminate species to either promote or inhibit precipitation.

Original language	English
Article number	120379
Journal	Journal of Molecular Liquids
Volume	367
DOIs	https://doi.org/10.1016/j.molliq.2022.120379
State	Published - Dec 1 2022

Funding

This work was supported by IDREAM (Interfacial Dynamics in Radioactive Environments and Materials), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES). The research at the NOMAD instrument, Spallation Neutron Source at Oak Ridge National Laboratory, was supported by the Scientific User Facilitates Division, BES, DOE. The research at the 11-ID-B beamline, Advanced Photon Source, Argonne National Laboratory was also supported by the Scientific User Facilitates Division, BES, DOE. Raman spectroscopy and NMR spectroscopy were performed using resources at the Environmental Molecular Sciences Laboratory (EMSL, grid.436923.9), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle Memorial Institute operating under Contract No. DE AC05-76RL0-1830.

Keywords

Aluminum
Homogenous nucleation
Hydrogen bonding
Neutron scattering
Oligomers
Solution chemistry

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10.1016/j.molliq.2022.120379

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title = "Structure and reactivity of sodium aluminate complexes in alkaline solutions",

abstract = "The underlying mechanism by which tetrahedrally-coordinated aluminate solution species react to precipitate octahedrally-coordinated Al3+ in gibbsite is unknown. Sodium aluminate solutions provide the opportunity to investigate the role of ion speciation and local structure in the reaction, as the solution metastability can be controlled by varying ratio of excess NaOD to Al3+. Here, capitalizing on this tunable precipitation behavior, aluminate speciation was investigated through a combination of Raman, infrared, and NMR spectroscopies, together with geometrical fitting of neutron and X-ray radial distribution functions. These techniques reveal a mixture of monomeric Al(OD)4− and dimeric Al2O(OD)62− in all compositions, but solutions avoiding precipitation for extended timescales (i.e. months to years) show an increased dimeric Al2O(OD)62− population formed at the expense of the Al(OD)4− monomer. Conversion between these species, as well the potential for further oligomerization and formation of larger pre-nucleation species is driven by the hydrogen/deuterium bonding (H/D-bonding) and proton/deuteron transfer reactions. Changes within the local environment around the aluminate anions, including solvation and the presence of solvent-shared ion pairs or contact ion pairs, will consequently govern the reactivity of these aluminate species to either promote or inhibit precipitation.",

keywords = "Aluminum, Homogenous nucleation, Hydrogen bonding, Neutron scattering, Oligomers, Solution chemistry",

author = "Nienhuis, {Emily T.} and Maxime Pouvreau and Graham, {Trent R.} and Prange, {Micah P.} and Katharine Page and Loring, {John S.} and Stack, {Andrew G.} and Clark, {Aurora E.} and Schenter, {Gregory K.} and Rosso, {Kevin M.} and Pearce, {Carolyn I.} and Wang, {Hsiu Wen}",

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doi = "10.1016/j.molliq.2022.120379",

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T1 - Structure and reactivity of sodium aluminate complexes in alkaline solutions

AU - Nienhuis, Emily T.

AU - Pouvreau, Maxime

AU - Graham, Trent R.

AU - Prange, Micah P.

AU - Page, Katharine

AU - Loring, John S.

AU - Stack, Andrew G.

AU - Clark, Aurora E.

AU - Schenter, Gregory K.

AU - Rosso, Kevin M.

AU - Pearce, Carolyn I.

AU - Wang, Hsiu Wen

PY - 2022/12/1

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AB - The underlying mechanism by which tetrahedrally-coordinated aluminate solution species react to precipitate octahedrally-coordinated Al3+ in gibbsite is unknown. Sodium aluminate solutions provide the opportunity to investigate the role of ion speciation and local structure in the reaction, as the solution metastability can be controlled by varying ratio of excess NaOD to Al3+. Here, capitalizing on this tunable precipitation behavior, aluminate speciation was investigated through a combination of Raman, infrared, and NMR spectroscopies, together with geometrical fitting of neutron and X-ray radial distribution functions. These techniques reveal a mixture of monomeric Al(OD)4− and dimeric Al2O(OD)62− in all compositions, but solutions avoiding precipitation for extended timescales (i.e. months to years) show an increased dimeric Al2O(OD)62− population formed at the expense of the Al(OD)4− monomer. Conversion between these species, as well the potential for further oligomerization and formation of larger pre-nucleation species is driven by the hydrogen/deuterium bonding (H/D-bonding) and proton/deuteron transfer reactions. Changes within the local environment around the aluminate anions, including solvation and the presence of solvent-shared ion pairs or contact ion pairs, will consequently govern the reactivity of these aluminate species to either promote or inhibit precipitation.

KW - Aluminum

KW - Homogenous nucleation

KW - Hydrogen bonding

KW - Neutron scattering

KW - Oligomers

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Structure and reactivity of sodium aluminate complexes in alkaline solutions

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Keywords

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