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

10 Scopus citations

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

Funding

† This manuscript has been authored in part 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). ‡ Electronic supplementary information (ESI) available: The details of the DFT-based electronic structure calculations, AIMD, and surface calorimetry measurements are given here. See DOI: 10.1039/d0cp00087f § Present address: TCS Research, Tata Research Development and Design Centre, 54-B Hadapsar Industrial Estate, Hadapsar, Pune-411013, Maharashtra, India. ¶ Present address: School of Molecular Sciences, The College of Liberal Arts and Sciences, and the School for Engineering of Matter, Transport and Energy, Arizona State University, Arizona, USA. E-mail: [email protected] This work was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office and used resources of the Oak Ridge Leadership Computing Facility and National Energy Research Scientific Computing Center (NERSC, U.S. Department of Energy Office of Science User Facility), which are respectively operated under Contract No. DE-AC05-00OR22725 and DE-AC02-05CH11231.

Fingerprint

Dive into the research topics of 'Hydration structure and water exchange kinetics at xenotime-water interfaces: Implications for rare earth minerals separation'. Together they form a unique fingerprint.

Cite this