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Title: Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate

Abstract

Iron oxides are ubiquitous in soils and sediments and play a critical role in the geochemical distribution of trace elements and heavy metals via adsorption and coprecipitation. The presence of organic acids may potentially alter how metals associate with iron oxide minerals through a series of cooperative or competitive processes: solution complexation, ternary surface complexation, and surface site competition. The macroscopic and molecular-scale effects of these processes were investigated for Ni adsorption to hematite and goethite at pH 7 in the presence of oxalate. The addition of this organic acid suppresses Ni uptake on both minerals. Aqueous speciation suggests that this is dominantly the result of oxalate complexing and solubilizing Ni. Comparison of the Ni surface coverage to the concentration of free (uncomplexed) Ni 2+ in solution suggests that the oxalate also alters Ni adsorption affinity. EXAFS and ATR-FTIR spectroscopies indicate that these changes in binding affinity are due to the formation of Ni–oxalate ternary surface complexes. These observations demonstrate that competition between dissolved oxalate and the mineral surface for Ni overwhelms the enhancement in adsorption associated with ternary complexation. Oxalate thus largely enhances Ni mobility, thereby increasing micronutrient bioavailability and inhibiting contaminant sequestration.

Authors:
 [1]; ORCiD logo [1]
  1. Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Science Foundation (NSF)
OSTI Identifier:
1379430
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 51; Journal Issue: 17
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Flynn, Elaine D., and Catalano, Jeffrey G. Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate. United States: N. p., 2017. Web. doi:10.1021/acs.est.7b02657.
Flynn, Elaine D., & Catalano, Jeffrey G. Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate. United States. doi:10.1021/acs.est.7b02657.
Flynn, Elaine D., and Catalano, Jeffrey G. Wed . "Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate". United States. doi:10.1021/acs.est.7b02657.
@article{osti_1379430,
title = {Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate},
author = {Flynn, Elaine D. and Catalano, Jeffrey G.},
abstractNote = {Iron oxides are ubiquitous in soils and sediments and play a critical role in the geochemical distribution of trace elements and heavy metals via adsorption and coprecipitation. The presence of organic acids may potentially alter how metals associate with iron oxide minerals through a series of cooperative or competitive processes: solution complexation, ternary surface complexation, and surface site competition. The macroscopic and molecular-scale effects of these processes were investigated for Ni adsorption to hematite and goethite at pH 7 in the presence of oxalate. The addition of this organic acid suppresses Ni uptake on both minerals. Aqueous speciation suggests that this is dominantly the result of oxalate complexing and solubilizing Ni. Comparison of the Ni surface coverage to the concentration of free (uncomplexed) Ni2+ in solution suggests that the oxalate also alters Ni adsorption affinity. EXAFS and ATR-FTIR spectroscopies indicate that these changes in binding affinity are due to the formation of Ni–oxalate ternary surface complexes. These observations demonstrate that competition between dissolved oxalate and the mineral surface for Ni overwhelms the enhancement in adsorption associated with ternary complexation. Oxalate thus largely enhances Ni mobility, thereby increasing micronutrient bioavailability and inhibiting contaminant sequestration.},
doi = {10.1021/acs.est.7b02657},
journal = {Environmental Science and Technology},
number = 17,
volume = 51,
place = {United States},
year = {Wed Aug 09 00:00:00 EDT 2017},
month = {Wed Aug 09 00:00:00 EDT 2017}
}