Sorption of selenium species onto phlogopite and calcite surfaces : DFT studies

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http://hdl.handle.net/10138/334264

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Puhakka , E , Li , X , Ikonen , J & Siitari-Kauppi , M 2019 , ' Sorption of selenium species onto phlogopite and calcite surfaces : DFT studies ' , Journal of Contaminant Hydrology , vol. 227 , 103553 , pp. 1-10 . https://doi.org/10.1016/j.jconhyd.2019.103553

Title: Sorption of selenium species onto phlogopite and calcite surfaces : DFT studies
Author: Puhakka, Eini; Li, Xiaodong; Ikonen, Jussi; Siitari-Kauppi, Marja
Contributor: University of Helsinki, Geological disposal of spent nuclear fuel
University of Helsinki, Department of Chemistry
University of Helsinki, Geological disposal of spent nuclear fuel
University of Helsinki, Department of Chemistry
Date: 2019-12
Language: eng
Number of pages: 10
Belongs to series: Journal of Contaminant Hydrology
ISSN: 0169-7722
URI: http://hdl.handle.net/10138/334264
Abstract: Sorption of Se(IV) and Se(VI) species onto Mg-rich biotite (phlogopite) and calcite surfaces was investigated using molecular modelling techniques. A CASTEP code implemented into Materials Studio was used to calculate the periodic systems, site densities and site types on the phlogopite and calcite surfaces. According to the results, the Se oxyanions attach to both edge and basal surfaces of phlogopite via an oxygen atom. However, calculated sorption energies indicate that surface complexation reactions via hydrogen bonding happen on the edge surfaces of phlogopite while cation exchange reactions happen on the basal surfaces of phlogopite. These reactions occur on the so-called weak sites according to the PHREEQC modelling. On the calcite surface, only cation exchange reactions are possible, and only for neutral Se species which do not occur in low saline groundwater conditions with pH 8–10. Biotite which is an abundant mineral in crystalline rock works fairly well as a sorbent but calcite which often exists on fracture surfaces of bedrock does not act as a sorbent for Se species.
Subject: ADSORPTION
Biotite
CESIUM
Calcite
DFT
IN-SITU
IONS
MATRIX DIFFUSION
MIGRATION
MONTMORILLONITE
OXYANIONS
PHOSPHATE
Phlogopite
Selenium
Sorption
WATER
116 Chemical sciences
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