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Title: Redox and complexation interactions of neptunium(V) with quinonoid-enriched humic derivatives

Abstract

Actinides in their higher valence states (e.g., MO{sub 2}{sup +} and MO{sub 2}{sup 2+}, where M can be Np, Pu, etc) possess a higher potential for migration and in turn pose a substantial environmental threat. To minimize this potential for migration, reducing them to lower oxidation states (e.g., their tetravalent state) can be an attractive and efficient remedial process. These lower oxidation states are often much less soluble in natural aqueous media and are, therefore, less mobile in the environment. The research presented here focuses on assessing the performance of quinonoid-enriched humic derivatives with regards to complexing and/or reducing Np(V) present in solution. These 'designer' humics are essentially derived reducing agents that can serve as reactive components of a novel humic-based remediation technology. The derivatives are obtained by incorporating different quinonoid-moieties into leonardite humic acids. Five quinonoid-derivatives are tested in this work and all five prove more effective as reducing agents for selected actinides than the parent leonardite humic acid, and the hydroquinone derivatives are better than the catechol derivatives. The reduction kinetics and the Np(V) species formed with the different derivatives are studied via a batch mode using near-infrared (NIR)-spectroscopy. Np(V) reduction by the humic derivatives under anoxic conditionsmore » at 293 K and at pH 4.7 obeys first-order kinetics. Rate constants range from 1.70 x 10{sup -6} (parent humic acid) to 1.06 x 10{sup -5} sec{sup -1} (derivative with maximum hydroquinone content). Stability constants for Np(V)-humic complexes calculated from spectroscopic data produce corresponding Log{beta} values of 2.3 for parent humic acid and values ranging from 2.5 to 3.2 at pH 4.7 and from 3.3 to 3.7 at pH 7.4 for humic derivatives. Maximum constants are observed for hydroquinone-enriched derivatives. It is concluded that among the humic derivatives tested, the hydroquinone-enriched ones are the most useful for addressing remedial needs of actinide-contaminated aquifers.« less

Authors:
 [1];  [2];  [2];  [2];  [1];  [3]
  1. Vernadsky Inst. of Geochemistry and Analytical Chemistry, Moscow, Russia
  2. Lomonosov Moscow State University, Moscow, Russia
  3. {Dick} G [ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
930924
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science & Technology; Journal Volume: 41; Journal Issue: 20
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ACTINIDES; AQUIFERS; HUMIC ACIDS; KINETICS; PERFORMANCE; REDUCING AGENTS; STABILITY; VALENCE

Citation Formats

Shcherbina, Natalia S., Perminova, Irina V., Kalmykov, Stephan N., Kovalenko, Anton N., Novikov, Alexander P., and Haire, Richard. Redox and complexation interactions of neptunium(V) with quinonoid-enriched humic derivatives. United States: N. p., 2007. Web. doi:10.1021/es070415l.
Shcherbina, Natalia S., Perminova, Irina V., Kalmykov, Stephan N., Kovalenko, Anton N., Novikov, Alexander P., & Haire, Richard. Redox and complexation interactions of neptunium(V) with quinonoid-enriched humic derivatives. United States. doi:10.1021/es070415l.
Shcherbina, Natalia S., Perminova, Irina V., Kalmykov, Stephan N., Kovalenko, Anton N., Novikov, Alexander P., and Haire, Richard. Mon . "Redox and complexation interactions of neptunium(V) with quinonoid-enriched humic derivatives". United States. doi:10.1021/es070415l.
@article{osti_930924,
title = {Redox and complexation interactions of neptunium(V) with quinonoid-enriched humic derivatives},
author = {Shcherbina, Natalia S. and Perminova, Irina V. and Kalmykov, Stephan N. and Kovalenko, Anton N. and Novikov, Alexander P. and Haire, Richard},
abstractNote = {Actinides in their higher valence states (e.g., MO{sub 2}{sup +} and MO{sub 2}{sup 2+}, where M can be Np, Pu, etc) possess a higher potential for migration and in turn pose a substantial environmental threat. To minimize this potential for migration, reducing them to lower oxidation states (e.g., their tetravalent state) can be an attractive and efficient remedial process. These lower oxidation states are often much less soluble in natural aqueous media and are, therefore, less mobile in the environment. The research presented here focuses on assessing the performance of quinonoid-enriched humic derivatives with regards to complexing and/or reducing Np(V) present in solution. These 'designer' humics are essentially derived reducing agents that can serve as reactive components of a novel humic-based remediation technology. The derivatives are obtained by incorporating different quinonoid-moieties into leonardite humic acids. Five quinonoid-derivatives are tested in this work and all five prove more effective as reducing agents for selected actinides than the parent leonardite humic acid, and the hydroquinone derivatives are better than the catechol derivatives. The reduction kinetics and the Np(V) species formed with the different derivatives are studied via a batch mode using near-infrared (NIR)-spectroscopy. Np(V) reduction by the humic derivatives under anoxic conditions at 293 K and at pH 4.7 obeys first-order kinetics. Rate constants range from 1.70 x 10{sup -6} (parent humic acid) to 1.06 x 10{sup -5} sec{sup -1} (derivative with maximum hydroquinone content). Stability constants for Np(V)-humic complexes calculated from spectroscopic data produce corresponding Log{beta} values of 2.3 for parent humic acid and values ranging from 2.5 to 3.2 at pH 4.7 and from 3.3 to 3.7 at pH 7.4 for humic derivatives. Maximum constants are observed for hydroquinone-enriched derivatives. It is concluded that among the humic derivatives tested, the hydroquinone-enriched ones are the most useful for addressing remedial needs of actinide-contaminated aquifers.},
doi = {10.1021/es070415l},
journal = {Environmental Science & Technology},
number = 20,
volume = 41,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}