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Title: Structure and reactivity of the calcite–water interface

Abstract

The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO 2 partial pressure. Changes in pH have only a weak effect in non–equilibrium solutions. The surface structure of (104) faces of single crystal calcite in contact to solutions corresponding to those of the zetapotential investigations is determined from surface diffraction measurements. The results reveal no direct indication of calcium or carbonate inner-sphere surface species. The surface ions are found to relax only slightly from their bulk positions; the most significant relaxation is a ~4° tilt of the surface carbonate ions towards the surface. Two ordered layers of water molecules are identified, the first at 2.35 ± 0.05 Å above surface calcium ions and the second layer at 3.24 ± 0.06 Å above the surface associated with surface carbonate ions. A Basic Stern surface complexation model is developed to model observed zetapotentials, while only considering outer–sphere complexes of ions other than protons and hydroxide. The Basicmore » Stern SCM successfully reproduces the zetapotential data and gives reasonable values for the inner Helmholtz capacitance, which are in line with the Stern layer thickness estimated from surface diffraction results.« less

Authors:
 [1];  [2];  [1];  [3];  [1];  [4]
  1. Karlsruher Inst. für Technologie, Karlsruhe (Germany)
  2. Univ. of Alaskan, Fairbanks, AK (United States)
  3. Univ. of Chicago, IL (United States). GeoSoilEnviroCars
  4. Forschungszentrum Julich (Germany). Inst. für Energieforschung
Publication Date:
Research Org.:
Univ. of Chicago, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; National Science Foundation (NSF)
OSTI Identifier:
1509824
Grant/Contract Number:  
FG02-94ER14466; AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Colloid and Interface Science
Additional Journal Information:
Journal Volume: 354; Journal Issue: 2; Journal ID: ISSN 0021-9797
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Synchrotron radiation; Calcite; Zetapotential; Surface diffraction; Crystal truncation rod; Surface complexation model

Citation Formats

Heberling, Frank, Trainor, Thomas P., Lützenkirchen, Johannes, Eng, Peter, Denecke, Melissa A., and Bosbach, Dirk. Structure and reactivity of the calcite–water interface. United States: N. p., 2010. Web. doi:10.1016/j.jcis.2010.10.047.
Heberling, Frank, Trainor, Thomas P., Lützenkirchen, Johannes, Eng, Peter, Denecke, Melissa A., & Bosbach, Dirk. Structure and reactivity of the calcite–water interface. United States. doi:10.1016/j.jcis.2010.10.047.
Heberling, Frank, Trainor, Thomas P., Lützenkirchen, Johannes, Eng, Peter, Denecke, Melissa A., and Bosbach, Dirk. Tue . "Structure and reactivity of the calcite–water interface". United States. doi:10.1016/j.jcis.2010.10.047. https://www.osti.gov/servlets/purl/1509824.
@article{osti_1509824,
title = {Structure and reactivity of the calcite–water interface},
author = {Heberling, Frank and Trainor, Thomas P. and Lützenkirchen, Johannes and Eng, Peter and Denecke, Melissa A. and Bosbach, Dirk},
abstractNote = {The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO2 partial pressure. Changes in pH have only a weak effect in non–equilibrium solutions. The surface structure of (104) faces of single crystal calcite in contact to solutions corresponding to those of the zetapotential investigations is determined from surface diffraction measurements. The results reveal no direct indication of calcium or carbonate inner-sphere surface species. The surface ions are found to relax only slightly from their bulk positions; the most significant relaxation is a ~4° tilt of the surface carbonate ions towards the surface. Two ordered layers of water molecules are identified, the first at 2.35 ± 0.05 Å above surface calcium ions and the second layer at 3.24 ± 0.06 Å above the surface associated with surface carbonate ions. A Basic Stern surface complexation model is developed to model observed zetapotentials, while only considering outer–sphere complexes of ions other than protons and hydroxide. The Basic Stern SCM successfully reproduces the zetapotential data and gives reasonable values for the inner Helmholtz capacitance, which are in line with the Stern layer thickness estimated from surface diffraction results.},
doi = {10.1016/j.jcis.2010.10.047},
journal = {Journal of Colloid and Interface Science},
number = 2,
volume = 354,
place = {United States},
year = {2010},
month = {10}
}

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