A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses

Robert C. Chapleski; Azhad U. Chowdhury; Anna K. Wanhala; Vera Bocharova; Santanu Roy; Philip C. Keller; Dylan Everly; Santa Jansone-Popova; Alexander Kisliuk; Robert L. Sacci; Andrew G. Stack; Corby G. Anderson; Benjamin Doughty; Vyacheslav S. Bryantsev

doi:10.1016/j.isci.2020.101435

A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses

Robert C. Chapleski, Azhad U. Chowdhury, Anna K. Wanhala, Vera Bocharova, Santanu Roy, Philip C. Keller, Dylan Everly, Santa Jansone-Popova, Alexander Kisliuk, Robert L. Sacci, Andrew G. Stack, Corby G. Anderson, Benjamin Doughty, Vyacheslav S. Bryantsev

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

16 Scopus citations

Abstract

Separating rare-earth-element-rich minerals from unwanted gangue in mined ores relies on selective binding of collector molecules at the interface to facilitate froth flotation. Salicylhydroxamic acid (SHA) exhibits enhanced selectivity for bastnäsite over calcite in microflotation experiments. Through a multifaceted approach, leveraging density functional theory calculations, and advanced spectroscopic methods, we provide molecular-level mechanistic insight to this selectivity. The hydroxamic acid moiety introduces strong interactions at metal-atom surface sites and hinders subsurface-cation stabilization at vacancy-defect sites, in calcite especially. Resulting from hydrogen-bond-induced interactions, SHA lies flat on the bastnäsite surface and shows a tendency for multilayer formation at high coverages. In this conformation, SHA complexation with bastnäsite metal ions is stabilized, leading to advanced flotation performance. In contrast, SHA lies perpendicular to the calcite surface due to a difference in cationic spacing. We anticipate that these insights will motivate rational design and selection of future collector molecules for enhanced ore beneficiation.

Original language	English
Article number	101435
Journal	iScience
Volume	23
Issue number	9
DOIs	https://doi.org/10.1016/j.isci.2020.101435
State	Published - Sep 25 2020

Funding

This research was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the US Department of Energy , Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231 . Sample preparation and Raman studies were supported by the US Department of Energy, Office of Science , Basic Energy Sciences , Materials Science and Engineering Division (R.L.S., V.B.). Special thanks to Alexandra Navrotsky at Arizona State University for providing synthetic bastnäsite samples. This research was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. Sample preparation and Raman studies were supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division (R.L.S. V.B.). Special thanks to Alexandra Navrotsky at Arizona State University for providing synthetic bastn?site samples. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). R.C.C. analyzed DFT results, prepared figures, and contributed to writing the paper. A.U.C. conducted vSFG experiments. A.K.W. conducted and analyzed ATR-FTIR experiments, prepared figures, and contributed to writing the paper. V.B. conducted and analyzed Raman experiments, provided figures, and contributed to writing the paper. S.R. contributed to DFT calculations. P.C.K. and D.E. conducted microflotation experiments. S.J.-P. identified hydroxamic acids for use in this project and distributed chemicals used in this work to team members. A.K. performed and analyzed Raman experiments. R.L.S. performed surface characterization and spectral analysis. A.G.S. and C.G.A. oversaw experiments and provided insights toward the manuscript. B.D. conducted and analyzed vSFG experiments and contributed to writing the paper. V.S.B. performed and analyzed DFT calculations and oversaw the collaboration leading to this manuscript. The authors declare no competing interests. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Funders	Funder number
Critical Materials Institute
DOE Public Access Plan
Materials Science and Engineering Division	DE-AC05-00OR22725
US Department of Energy
US Department of Energy Office of Science
U.S. Department of Energy	DE-AC02-05CH11231
Advanced Manufacturing Office
Office of Science
Office of Energy Efficiency and Renewable Energy
Basic Energy Sciences
Division of Materials Sciences and Engineering

Keywords

Chemical Engineering
Physical Inorganic Chemistry
Spectroscopy
Surface Chemistry

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10.1016/j.isci.2020.101435

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Chapleski, R. C., Chowdhury, A. U., Wanhala, A. K., Bocharova, V., Roy, S., Keller, P. C., Everly, D., Jansone-Popova, S., Kisliuk, A., Sacci, R. L., Stack, A. G., Anderson, C. G., Doughty, B., & Bryantsev, V. S. (2020). A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses. iScience, 23(9), Article 101435. https://doi.org/10.1016/j.isci.2020.101435

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title = "A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses",

abstract = "Separating rare-earth-element-rich minerals from unwanted gangue in mined ores relies on selective binding of collector molecules at the interface to facilitate froth flotation. Salicylhydroxamic acid (SHA) exhibits enhanced selectivity for bastn{\"a}site over calcite in microflotation experiments. Through a multifaceted approach, leveraging density functional theory calculations, and advanced spectroscopic methods, we provide molecular-level mechanistic insight to this selectivity. The hydroxamic acid moiety introduces strong interactions at metal-atom surface sites and hinders subsurface-cation stabilization at vacancy-defect sites, in calcite especially. Resulting from hydrogen-bond-induced interactions, SHA lies flat on the bastn{\"a}site surface and shows a tendency for multilayer formation at high coverages. In this conformation, SHA complexation with bastn{\"a}site metal ions is stabilized, leading to advanced flotation performance. In contrast, SHA lies perpendicular to the calcite surface due to a difference in cationic spacing. We anticipate that these insights will motivate rational design and selection of future collector molecules for enhanced ore beneficiation.",

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AU - Bocharova, Vera

AU - Roy, Santanu

AU - Keller, Philip C.

AU - Everly, Dylan

AU - Jansone-Popova, Santa

AU - Kisliuk, Alexander

AU - Sacci, Robert L.

AU - Stack, Andrew G.

AU - Anderson, Corby G.

AU - Doughty, Benjamin

AU - Bryantsev, Vyacheslav S.

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N2 - Separating rare-earth-element-rich minerals from unwanted gangue in mined ores relies on selective binding of collector molecules at the interface to facilitate froth flotation. Salicylhydroxamic acid (SHA) exhibits enhanced selectivity for bastnäsite over calcite in microflotation experiments. Through a multifaceted approach, leveraging density functional theory calculations, and advanced spectroscopic methods, we provide molecular-level mechanistic insight to this selectivity. The hydroxamic acid moiety introduces strong interactions at metal-atom surface sites and hinders subsurface-cation stabilization at vacancy-defect sites, in calcite especially. Resulting from hydrogen-bond-induced interactions, SHA lies flat on the bastnäsite surface and shows a tendency for multilayer formation at high coverages. In this conformation, SHA complexation with bastnäsite metal ions is stabilized, leading to advanced flotation performance. In contrast, SHA lies perpendicular to the calcite surface due to a difference in cationic spacing. We anticipate that these insights will motivate rational design and selection of future collector molecules for enhanced ore beneficiation.

AB - Separating rare-earth-element-rich minerals from unwanted gangue in mined ores relies on selective binding of collector molecules at the interface to facilitate froth flotation. Salicylhydroxamic acid (SHA) exhibits enhanced selectivity for bastnäsite over calcite in microflotation experiments. Through a multifaceted approach, leveraging density functional theory calculations, and advanced spectroscopic methods, we provide molecular-level mechanistic insight to this selectivity. The hydroxamic acid moiety introduces strong interactions at metal-atom surface sites and hinders subsurface-cation stabilization at vacancy-defect sites, in calcite especially. Resulting from hydrogen-bond-induced interactions, SHA lies flat on the bastnäsite surface and shows a tendency for multilayer formation at high coverages. In this conformation, SHA complexation with bastnäsite metal ions is stabilized, leading to advanced flotation performance. In contrast, SHA lies perpendicular to the calcite surface due to a difference in cationic spacing. We anticipate that these insights will motivate rational design and selection of future collector molecules for enhanced ore beneficiation.

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A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses

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