Hydration structure and water exchange kinetics at xenotime-water interfaces: Implications for rare earth minerals separation

Santanu Roy, Lili Wu, Sriram Goverapet Srinivasan, Andrew G. Stack, Alexandra Navrotsky, Vyacheslav S. Bryantsev

Research output: Contribution to journalArticlepeer-review

Abstract

Hydration of surface ions gives rise to structural heterogeneity and variable exchange kinetics of water at complex mineral-water interfaces. Here, we employ ab initio molecular dynamics (AIMD) simulations and water adsorption calorimetry to examine the aqueous interfaces of xenotime, a phosphate mineral that contains predominantly Y3+ and heavy rare earth elements. Consistent with natural crystal morphology, xenotime is predicted to have a tetragonal prismatic shape, dominated by the {100} surface. Hydration of this surface induces multilayer interfacial water structures with distinct OH orientations, which agrees with recent crystal truncation rod measurements. The exchange kinetics between two adjacent water layers exhibits a wide range of underlying timescales (5-180 picoseconds), dictated by ion-water electrostatics. Adsorption of a bidentate hydroxamate ligand reveals that {100} xenotime surface can only accommodate monodentate coordination with water exchange kinetics strongly depending on specific ligand orientation, prompting us to reconsider traditional strategies for selective separation of rare-earth minerals.

Original languageEnglish (US)
Pages (from-to)7719-7727
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume22
Issue number15
DOIs
StatePublished - Apr 21 2020

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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