Electrostatic Potential of Specific Mineral Faces

Reaction rates of environmental processes occurring at hydrated mineral surfaces are in part controlled by the electrostatic potential that develops at the interface. This potential depends on the structure of exposed crystal faces as well as the pH and the type of ions and their interactions with t...

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Bibliographic Details
Published in:Langmuir 2011-07, Vol.27 (13), p.7986-7990
Main Authors: Zarzycki, P, Chatman, S, Preočanin, T, Rosso, K. M
Format: Article
Language:English
Subjects:
Chemistry
computer simulations
CONSTRUCTION
ELECTRODES
electron transfer
ELECTROSTATICS
Environmental Molecular Sciences Laboratory
Exact sciences and technology
General and physical chemistry
GEOSCIENCES
HEMATITE
HYSTERESIS
metal oxide
Nernst potential
REACTION KINETICS
single-crystal electrode
Surface physical chemistry
surface potential
TESTING
THERMODYNAMICS
TITRATION
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Summary:Reaction rates of environmental processes occurring at hydrated mineral surfaces are in part controlled by the electrostatic potential that develops at the interface. This potential depends on the structure of exposed crystal faces as well as the pH and the type of ions and their interactions with these faces. Despite its importance, experimental methods for determining fundamental electrostatic properties of specific crystal faces such as the point of zero charge are few. Here we show that this information may be obtained from simple, cyclic potentiometric titration using a well-characterized single-crystal electrode exposing the face of interest. The method exploits the presence of a hysteresis loop in the titration measurements that allows the extraction of key electrostatic descriptors using the Maxwell construction. The approach is demonstrated for hematite (α-Fe2O3) (001), and thermodynamic proof is provided for the resulting estimate of its point of zero charge. Insight gained from this method will aid in predicting the fate of migrating contaminants, mineral growth/dissolution processes, and mineral–microbiological interactions and in testing surface complexation theories.
ISSN:0743-7463
1520-5827
DOI:10.1021/la201369g