期刊
JOURNAL OF COLLOID AND INTERFACE SCIENCE
卷 391, 期 -, 页码 125-134出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2012.09.081
关键词
Hematite; Single crystal; Titration; Protonation; Hysteresis; Site complexation
资金
- US Department of Energy (DOE), Office of Basic Energy Sciences, Geosciences Program
- DOE Office of Biological and Environmental Research at Pacific Northwest National Laboratory
- Ministry of Science, Education and Sports of the Republic of Croatia [119-1191342-2961]
Time dependent potentiometric pH titrations were used to study the effect of atomic scale surface structure on the protonation behavior of the structurally well-defined hematite/electrolyte interfaces. Our recently proposed thermodynamic model [1,25] was applied to measured acidimetric and alkalimetric titration hysteresis loops, collected from highly organized (001), (012), and (113) crystal face terminations using pH equilibration times ranging from 15 to 30 min. Hysteresis loop areas indicate that (001) faces equilibrate faster than the (012) and (113) faces, consistent with the different expected ensembles of singly-, doubly-, and triply-coordinated surface sites on each face. Strongly non-linear hysteretic pH-potential relationships were found, with slopes exceeding Nernstian, collectively indicating that protonation and deprotonation is much more complex than embodied in present day surface complexation models. The asymmetrical shape of the acidimetric and alkalimetric titration branches were used to illustrate a proposed steric leaky screen repulsion/trapping interaction mechanism that stems from high affinity singly-coordinated sites electrostatically and sterically screening lower affinity doubly- and triply-coordinated sites. Our data indicate that site interaction is the dominant phenomenon defining surface potential accumulation behavior on single crystal faces of metal oxide minerals. (C) 2012 Elsevier Inc. All rights reserved.
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