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Phosphate effects on rare earth element sorption onto kaolinite: molecular-scale insights at circumneutral pH.

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Title: Phosphate effects on rare earth element sorption onto kaolinite: molecular-scale insights at circumneutral pH.
Authors: Xu, Hang1 (AUTHOR), Leisen, Johannes2 (AUTHOR), Robang, Alicia S.3 (AUTHOR), Wen, Yinghao1 (AUTHOR), Wan, Biao4 (AUTHOR), Zhao, Simin1 (AUTHOR), Paravastu, Anant3 (AUTHOR), Phillips, Brian L.5 (AUTHOR), Tang, Yuanzhi1 (AUTHOR) yuanzhi.tang@eas.gatech.edu
Source: Geochimica et Cosmochimica Acta. Nov2025, Vol. 408, p132-143. 12p.
Subjects: Phosphates, Rare earth metals, Molecular dynamics, Sorption, Yttrium, Surface interactions, Kaolinite
Abstract: Rare earth elements (REEs) are critical minerals that are indispensable for the clean energy transition. Understanding their occurrence and behavior in highly weathered environments provides valuable insights into the identification and prediction of potential REE resources. Phosphate (P) plays an important role in controlling the geochemical behaviors of REE during weathering and secondary deposition. REE-phosphate minerals, such as monazite and xenotime, are among the important natural sources of REE. However, the molecular-scale reaction mechanisms underlying phosphate-REE interactions in weathering environments remain unclear. This study investigates the interaction between phosphate and yttrium on the surface of kaolinite, a representative and abundant clay mineral in highly weathered environments. At circumneutral pH 6, phosphate inhibits yttrium mobilization by forming ternary kaolinite-yttrium-phosphate complexes and surface precipitation. The reaction mechanisms identified in this study are distinct from previously reported adsorption-dominated processes on clay minerals that govern REE immobilization during chemical weathering. Solid-state nuclear magnetic resonance (NMR) spectroscopy, including 31P direct polarization magic angle spinning (DP/MAS) and 1H – 31P cross polarization (CP) rotational echo adiabatic passage double resonance (REAPDOR) analyses, provides direct molecular-scale evidence for the yttrium-phosphate surface complexation on kaolinite. Quantification of atomic distances by numerical simulations further substantiates the formation of ternary surface complexes. These mechanistic findings enhance our understanding of phosphate-mediated REE mobilization, transport, and redeposition in natural environments. [ABSTRACT FROM AUTHOR]
Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 188829787
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PubType: Academic Journal
PubTypeId: academicJournal
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Items – Name: Title
  Label: Title
  Group: Ti
  Data: Phosphate effects on rare earth element sorption onto kaolinite: molecular-scale insights at circumneutral pH.
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  Data: <searchLink fieldCode="AR" term="%22Xu%2C+Hang%22">Xu, Hang</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Leisen%2C+Johannes%22">Leisen, Johannes</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Robang%2C+Alicia+S%2E%22">Robang, Alicia S.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Wen%2C+Yinghao%22">Wen, Yinghao</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Wan%2C+Biao%22">Wan, Biao</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Zhao%2C+Simin%22">Zhao, Simin</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Paravastu%2C+Anant%22">Paravastu, Anant</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Phillips%2C+Brian+L%2E%22">Phillips, Brian L.</searchLink><relatesTo>5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Tang%2C+Yuanzhi%22">Tang, Yuanzhi</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> yuanzhi.tang@eas.gatech.edu</i>
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  Data: <searchLink fieldCode="JN" term="%22Geochimica+et+Cosmochimica+Acta%22">Geochimica et Cosmochimica Acta</searchLink>. Nov2025, Vol. 408, p132-143. 12p.
– Name: Subject
  Label: Subjects
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  Data: <searchLink fieldCode="DE" term="%22Phosphates%22">Phosphates</searchLink><br /><searchLink fieldCode="DE" term="%22Rare+earth+metals%22">Rare earth metals</searchLink><br /><searchLink fieldCode="DE" term="%22Molecular+dynamics%22">Molecular dynamics</searchLink><br /><searchLink fieldCode="DE" term="%22Sorption%22">Sorption</searchLink><br /><searchLink fieldCode="DE" term="%22Yttrium%22">Yttrium</searchLink><br /><searchLink fieldCode="DE" term="%22Surface+interactions%22">Surface interactions</searchLink><br /><searchLink fieldCode="DE" term="%22Kaolinite%22">Kaolinite</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Rare earth elements (REEs) are critical minerals that are indispensable for the clean energy transition. Understanding their occurrence and behavior in highly weathered environments provides valuable insights into the identification and prediction of potential REE resources. Phosphate (P) plays an important role in controlling the geochemical behaviors of REE during weathering and secondary deposition. REE-phosphate minerals, such as monazite and xenotime, are among the important natural sources of REE. However, the molecular-scale reaction mechanisms underlying phosphate-REE interactions in weathering environments remain unclear. This study investigates the interaction between phosphate and yttrium on the surface of kaolinite, a representative and abundant clay mineral in highly weathered environments. At circumneutral pH 6, phosphate inhibits yttrium mobilization by forming ternary kaolinite-yttrium-phosphate complexes and surface precipitation. The reaction mechanisms identified in this study are distinct from previously reported adsorption-dominated processes on clay minerals that govern REE immobilization during chemical weathering. Solid-state nuclear magnetic resonance (NMR) spectroscopy, including 31P direct polarization magic angle spinning (DP/MAS) and 1H – 31P cross polarization (CP) rotational echo adiabatic passage double resonance (REAPDOR) analyses, provides direct molecular-scale evidence for the yttrium-phosphate surface complexation on kaolinite. Quantification of atomic distances by numerical simulations further substantiates the formation of ternary surface complexes. These mechanistic findings enhance our understanding of phosphate-mediated REE mobilization, transport, and redeposition in natural environments. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Geochimica et Cosmochimica Acta is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1016/j.gca.2025.09.040
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 12
        StartPage: 132
    Subjects:
      – SubjectFull: Phosphates
        Type: general
      – SubjectFull: Rare earth metals
        Type: general
      – SubjectFull: Molecular dynamics
        Type: general
      – SubjectFull: Sorption
        Type: general
      – SubjectFull: Yttrium
        Type: general
      – SubjectFull: Surface interactions
        Type: general
      – SubjectFull: Kaolinite
        Type: general
    Titles:
      – TitleFull: Phosphate effects on rare earth element sorption onto kaolinite: molecular-scale insights at circumneutral pH.
        Type: main
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            NameFull: Xu, Hang
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            NameFull: Leisen, Johannes
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            NameFull: Robang, Alicia S.
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            NameFull: Wen, Yinghao
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            NameFull: Wan, Biao
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            – D: 01
              M: 11
              Text: Nov2025
              Type: published
              Y: 2025
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              Value: 408
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