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Title: Probing size-dependent electrokinetics of hematite aggregates

Abstract

Aqueous particle suspensions of many kinds are stabilized by the electrostatic potential developed at their surfaces from reaction with water and ions. An important and less well understood aspect of this stabilization is the dependence of the electrostatic surface potential on particle size. Surface electrostatics are typically probed by measuring particle electrophoretic mobilities and quantified in the electrokinetic potential (f), using commercially available Zeta Potential Analyzers (ZPA). Even though ZPAs provide frequency-spectra (histograms) of electrophoretic mobility and hydrodynamic diameter, typically only the maximal-intensity values are reported, despite the information in the remainder of the spectra. Here we propose a mapping procedure that inter-correlates these histograms to extract additional insight, in this case to probe particle size-dependent electrokinetics. Our method is illustrated for a suspension of prototypical iron (III) oxide (hematite, a-Fe2O3). We found that the electrophoretic mobility and f-potential are a linear function of the aggregate size. By analyzing the distribution of surface site types as a function of aggregate size we show that site coordination increases with increasing aggregate diameter. This observation explains why the acidity of the iron oxide particles decreases with increasing particle size.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1372971
Report Number(s):
PNNL-SA-125768
Journal ID: ISSN 0021-9797; 47824; KC0302060
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Colloid and Interface Science
Additional Journal Information:
Journal Volume: 488; Journal Issue: C; Journal ID: ISSN 0021-9797
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory

Citation Formats

Kedra-Królik, Karolina, Rosso, Kevin M., and Zarzycki, Piotr. Probing size-dependent electrokinetics of hematite aggregates. United States: N. p., 2017. Web. doi:10.1016/j.jcis.2016.11.004.
Kedra-Królik, Karolina, Rosso, Kevin M., & Zarzycki, Piotr. Probing size-dependent electrokinetics of hematite aggregates. United States. https://doi.org/10.1016/j.jcis.2016.11.004
Kedra-Królik, Karolina, Rosso, Kevin M., and Zarzycki, Piotr. 2017. "Probing size-dependent electrokinetics of hematite aggregates". United States. https://doi.org/10.1016/j.jcis.2016.11.004.
@article{osti_1372971,
title = {Probing size-dependent electrokinetics of hematite aggregates},
author = {Kedra-Królik, Karolina and Rosso, Kevin M. and Zarzycki, Piotr},
abstractNote = {Aqueous particle suspensions of many kinds are stabilized by the electrostatic potential developed at their surfaces from reaction with water and ions. An important and less well understood aspect of this stabilization is the dependence of the electrostatic surface potential on particle size. Surface electrostatics are typically probed by measuring particle electrophoretic mobilities and quantified in the electrokinetic potential (f), using commercially available Zeta Potential Analyzers (ZPA). Even though ZPAs provide frequency-spectra (histograms) of electrophoretic mobility and hydrodynamic diameter, typically only the maximal-intensity values are reported, despite the information in the remainder of the spectra. Here we propose a mapping procedure that inter-correlates these histograms to extract additional insight, in this case to probe particle size-dependent electrokinetics. Our method is illustrated for a suspension of prototypical iron (III) oxide (hematite, a-Fe2O3). We found that the electrophoretic mobility and f-potential are a linear function of the aggregate size. By analyzing the distribution of surface site types as a function of aggregate size we show that site coordination increases with increasing aggregate diameter. This observation explains why the acidity of the iron oxide particles decreases with increasing particle size.},
doi = {10.1016/j.jcis.2016.11.004},
url = {https://www.osti.gov/biblio/1372971}, journal = {Journal of Colloid and Interface Science},
issn = {0021-9797},
number = C,
volume = 488,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}