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Title: Inorganic ligand effects on Pb(II) sorption to goethite ({alpha}-FeOOH). 1. Carbonate

Abstract

Macroscopic measurements show that Pb(II) uptake on iron(hydr)oxides can be altered significantly by dissolved carbonate (enhanced up to 18% at pH 5 and decreased above pH {approximately}6.5 in analyses at 1 atm CO{sub 2}). This study elucidates the molecular-scale processes giving rise to these macroscopic effects by characterizing the structures of Pb(II) sorption complexes formed on geothite ({alpha}-FeOOH) in the presence of carbonate using in situ Pb L{sub III}-EXAFS and ATR-FTIR spectroscopies. Bond valence and structural constraints are applied to develop mineral surface site-specific models for Pb sorption. Under all conditions studied, Pb(II) forms predominantly inner-sphere edge-sharing (bidentate and/or tridentate) complexes with Fe(O,OH){sub 6} octahedra. Corner-sharing complexes are observed only in low pH (5) samples. Consistent with this pH sensitivity, site-specific analyses suggest that the relative abundance of corner-sharing sites reflects changes in the proton affinity of triply coordinated sites on the goethite (110) surface as suggested previously. FTIR results suggest the existence of ternary surface complexes in which carbonate groups bond to Pb as monodentate ligands. EXAFS data indicate that these ternary complexes are bound to the surface through Pb, forming metal-bridged (Type A) complexes. Findings are summarized as structural models and corresponding mineral surface site-specific chemical reactions.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Stanford Univ., CA (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20080258
DOE Contract Number:  
FG03-93ER14347
Resource Type:
Journal Article
Journal Name:
Journal of Colloid and Interface Science
Additional Journal Information:
Journal Volume: 225; Journal Issue: 2; Other Information: PBD: 15 May 2000; Journal ID: ISSN 0021-9797
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; LIGANDS; LEAD; SORPTION; GOETHITE; CARBONATES; MOLECULAR STRUCTURE; SORPTIVE PROPERTIES; ENVIRONMENTAL TRANSPORT

Citation Formats

Ostergren, J.D., Trainor, T.P., Bargar, J.R., Brown, G.E. Jr., and Parks, G.A. Inorganic ligand effects on Pb(II) sorption to goethite ({alpha}-FeOOH). 1. Carbonate. United States: N. p., 2000. Web. doi:10.1006/jcis.1999.6701.
Ostergren, J.D., Trainor, T.P., Bargar, J.R., Brown, G.E. Jr., & Parks, G.A. Inorganic ligand effects on Pb(II) sorption to goethite ({alpha}-FeOOH). 1. Carbonate. United States. doi:10.1006/jcis.1999.6701.
Ostergren, J.D., Trainor, T.P., Bargar, J.R., Brown, G.E. Jr., and Parks, G.A. Mon . "Inorganic ligand effects on Pb(II) sorption to goethite ({alpha}-FeOOH). 1. Carbonate". United States. doi:10.1006/jcis.1999.6701.
@article{osti_20080258,
title = {Inorganic ligand effects on Pb(II) sorption to goethite ({alpha}-FeOOH). 1. Carbonate},
author = {Ostergren, J.D. and Trainor, T.P. and Bargar, J.R. and Brown, G.E. Jr. and Parks, G.A.},
abstractNote = {Macroscopic measurements show that Pb(II) uptake on iron(hydr)oxides can be altered significantly by dissolved carbonate (enhanced up to 18% at pH 5 and decreased above pH {approximately}6.5 in analyses at 1 atm CO{sub 2}). This study elucidates the molecular-scale processes giving rise to these macroscopic effects by characterizing the structures of Pb(II) sorption complexes formed on geothite ({alpha}-FeOOH) in the presence of carbonate using in situ Pb L{sub III}-EXAFS and ATR-FTIR spectroscopies. Bond valence and structural constraints are applied to develop mineral surface site-specific models for Pb sorption. Under all conditions studied, Pb(II) forms predominantly inner-sphere edge-sharing (bidentate and/or tridentate) complexes with Fe(O,OH){sub 6} octahedra. Corner-sharing complexes are observed only in low pH (5) samples. Consistent with this pH sensitivity, site-specific analyses suggest that the relative abundance of corner-sharing sites reflects changes in the proton affinity of triply coordinated sites on the goethite (110) surface as suggested previously. FTIR results suggest the existence of ternary surface complexes in which carbonate groups bond to Pb as monodentate ligands. EXAFS data indicate that these ternary complexes are bound to the surface through Pb, forming metal-bridged (Type A) complexes. Findings are summarized as structural models and corresponding mineral surface site-specific chemical reactions.},
doi = {10.1006/jcis.1999.6701},
journal = {Journal of Colloid and Interface Science},
issn = {0021-9797},
number = 2,
volume = 225,
place = {United States},
year = {2000},
month = {5}
}