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Title: Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles

Abstract

As part of a study of the effect of particle size on reactivity of hematite to aqueous metal ions, the sorption of Zn(II) on hematite nanoparticles and microparticles was examined over a wide range of Zn(II) concentrations using Zn K-edge EXAFS. When reacted with nanoparticles at pH 5.5 and low Zn(II) sorption densities (0.04 {le} {Lambda} < 2.76 imol/m{sup 2}), Zn(II) formed five-coordinated or a mixture of four- and six-coordinated surface complexes with an average Zn-O distance of 2.04({+-}0.02){angstrom}. At pH 5.5 and high Zn(II) sorption densities (2.76 {ge} {Lambda} {le} 3.70 mol/m{sup 2}), formation of surface precipitates is suggested based on the presence of second-shell Zn and multiple scattering features in the Fourier transform (FT) of the EXAFS spectra. EXAFS fitting of these high {Lambda} samples yielded an average first-shell Zn-O distance of 2.10({+-}0.02){angstrom}, with second-shell Zn-Fe and Zn-Zn distances of 3.23({+-}0.03){angstrom} and 3.31({+-}0.03){angstrom}, respectively. Qualitative comparison between the EXAFS spectra of these sorption samples and that of amorphous zinc hydroxide and Zn-bearing hydrotalcite indicates the development of surface precipitates with increasing {Lambda}. EXAFS spectra of Zn(II) sorbed on hematite microparticles under similar experimental conditions showed no evidence for surface precipitates even at the highest Zn surface coverage ({Lambda}more » = 4 {micro}mol/m{sup 2}). These results indicate that reactivities of hematite nanoparticles and macroparticles differ with respect to Zn(II)aq, depending on Zn(II) sorption density. We suggest that the degree of hematite crystallinity affects the reactivity of hematite surfaces toward Zn(II)aq and the formation of the Zn(II) surface complexes.« less

Authors:
; ;
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
896408
Report Number(s):
SLAC-PUB-12226
TRN: US200703%%453
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Contributed to 13th International Conference on X-ray Absorption Fine Structure (XAFS13), Stanford, California, 9-14 Jul 2006
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 58 GEOSCIENCES; ADSORPTION; HEMATITE; MULTIPLE SCATTERING; PARTICLE SIZE; PRECIPITATION; SORPTION; SPECTRA; ZINC COMPOUNDS; SORPTIVE PROPERTIES; Other,BIO

Citation Formats

Ha, Juyong, /Stanford U., Geo. Environ. Sci., Farges, Francois, /Stanford U., Geo. Environ. Sci. /Museum Nat. Hist., Paris, Brown, Jr, Gordon E, and /SLAC, SSRL. Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles. United States: N. p., 2006. Web.
Ha, Juyong, /Stanford U., Geo. Environ. Sci., Farges, Francois, /Stanford U., Geo. Environ. Sci. /Museum Nat. Hist., Paris, Brown, Jr, Gordon E, & /SLAC, SSRL. Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles. United States.
Ha, Juyong, /Stanford U., Geo. Environ. Sci., Farges, Francois, /Stanford U., Geo. Environ. Sci. /Museum Nat. Hist., Paris, Brown, Jr, Gordon E, and /SLAC, SSRL. 2006. "Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles". United States. https://www.osti.gov/servlets/purl/896408.
@article{osti_896408,
title = {Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles},
author = {Ha, Juyong and /Stanford U., Geo. Environ. Sci. and Farges, Francois and /Stanford U., Geo. Environ. Sci. /Museum Nat. Hist., Paris and Brown, Jr, Gordon E and /SLAC, SSRL},
abstractNote = {As part of a study of the effect of particle size on reactivity of hematite to aqueous metal ions, the sorption of Zn(II) on hematite nanoparticles and microparticles was examined over a wide range of Zn(II) concentrations using Zn K-edge EXAFS. When reacted with nanoparticles at pH 5.5 and low Zn(II) sorption densities (0.04 {le} {Lambda} < 2.76 imol/m{sup 2}), Zn(II) formed five-coordinated or a mixture of four- and six-coordinated surface complexes with an average Zn-O distance of 2.04({+-}0.02){angstrom}. At pH 5.5 and high Zn(II) sorption densities (2.76 {ge} {Lambda} {le} 3.70 mol/m{sup 2}), formation of surface precipitates is suggested based on the presence of second-shell Zn and multiple scattering features in the Fourier transform (FT) of the EXAFS spectra. EXAFS fitting of these high {Lambda} samples yielded an average first-shell Zn-O distance of 2.10({+-}0.02){angstrom}, with second-shell Zn-Fe and Zn-Zn distances of 3.23({+-}0.03){angstrom} and 3.31({+-}0.03){angstrom}, respectively. Qualitative comparison between the EXAFS spectra of these sorption samples and that of amorphous zinc hydroxide and Zn-bearing hydrotalcite indicates the development of surface precipitates with increasing {Lambda}. EXAFS spectra of Zn(II) sorbed on hematite microparticles under similar experimental conditions showed no evidence for surface precipitates even at the highest Zn surface coverage ({Lambda} = 4 {micro}mol/m{sup 2}). These results indicate that reactivities of hematite nanoparticles and macroparticles differ with respect to Zn(II)aq, depending on Zn(II) sorption density. We suggest that the degree of hematite crystallinity affects the reactivity of hematite surfaces toward Zn(II)aq and the formation of the Zn(II) surface complexes.},
doi = {},
url = {https://www.osti.gov/biblio/896408}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Dec 13 00:00:00 EST 2006},
month = {Wed Dec 13 00:00:00 EST 2006}
}

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