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Title: The link between clay mineral weathering and the stabilization of Ni surface precipitates

Abstract

The formation of transition-metal surface precipitates may occur during sorption to clay minerals under ambient soil conditions. This process may lead to significant long-term stabilization of the metal within the soil profile. However, the rates and mechanisms controlling surface precipitate formation are poorly understood. The authors monitored changes in the reversibility of Ni sorbed to a clay mineral, pyrophyllite, in model batch experiments maintained at pH 7.5 for up to 1 year. The macroscopic sorption and dissolution study was complemented by a time-resolved characterization of the sorbed phase via spectroscopic and thermal methods. They found that nickel became increasingly resistant, over time, to extraction with EDTA. Initially, the sorbed phase consisted of a Ni-Al layered double hydroxide (LDH). With time, the anionic species in the interlayer space of the LDH changed from nitrate to silica polymers transforming the LDH gradually into a precursor Ni-Al phyllosilicate. The authors believe that this phase transformation is responsible for a substantial part of the observed increase in dissolution resistance. Thus, clay mineral weathering and the time-dependent release of Al and Si ions controlled Ni precipitate nucleation and transformation. The results suggest a potential pathway for long-term Ni stabilization in soil.

Authors:
; ; ;  [1]
  1. Univ. of Delaware, Newark, DE (United States). Dept. of Plant and Soil Sciences
Publication Date:
OSTI Identifier:
687353
Resource Type:
Journal Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 33; Journal Issue: 18; Other Information: PBD: 15 Sep 1999
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; NICKEL; LAND POLLUTION; SOIL CHEMISTRY; WEATHERING; CLAYS; ALUMINIUM; SILICON; SORPTION; STABILIZATION

Citation Formats

Ford, R.G., Scheinost, A.C., Scheckel, K.G., and Sparks, D.L. The link between clay mineral weathering and the stabilization of Ni surface precipitates. United States: N. p., 1999. Web. doi:10.1021/es990271d.
Ford, R.G., Scheinost, A.C., Scheckel, K.G., & Sparks, D.L. The link between clay mineral weathering and the stabilization of Ni surface precipitates. United States. doi:10.1021/es990271d.
Ford, R.G., Scheinost, A.C., Scheckel, K.G., and Sparks, D.L. Wed . "The link between clay mineral weathering and the stabilization of Ni surface precipitates". United States. doi:10.1021/es990271d.
@article{osti_687353,
title = {The link between clay mineral weathering and the stabilization of Ni surface precipitates},
author = {Ford, R.G. and Scheinost, A.C. and Scheckel, K.G. and Sparks, D.L.},
abstractNote = {The formation of transition-metal surface precipitates may occur during sorption to clay minerals under ambient soil conditions. This process may lead to significant long-term stabilization of the metal within the soil profile. However, the rates and mechanisms controlling surface precipitate formation are poorly understood. The authors monitored changes in the reversibility of Ni sorbed to a clay mineral, pyrophyllite, in model batch experiments maintained at pH 7.5 for up to 1 year. The macroscopic sorption and dissolution study was complemented by a time-resolved characterization of the sorbed phase via spectroscopic and thermal methods. They found that nickel became increasingly resistant, over time, to extraction with EDTA. Initially, the sorbed phase consisted of a Ni-Al layered double hydroxide (LDH). With time, the anionic species in the interlayer space of the LDH changed from nitrate to silica polymers transforming the LDH gradually into a precursor Ni-Al phyllosilicate. The authors believe that this phase transformation is responsible for a substantial part of the observed increase in dissolution resistance. Thus, clay mineral weathering and the time-dependent release of Al and Si ions controlled Ni precipitate nucleation and transformation. The results suggest a potential pathway for long-term Ni stabilization in soil.},
doi = {10.1021/es990271d},
journal = {Environmental Science and Technology},
number = 18,
volume = 33,
place = {United States},
year = {1999},
month = {9}
}