The link between clay mineral weathering and the stabilization of Ni surface precipitates
Journal Article
·
· Environmental Science and Technology
- Univ. of Delaware, Newark, DE (United States). Dept. of Plant and Soil Sciences
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.
- OSTI ID:
- 687353
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 18 Vol. 33; ISSN 0013-936X; ISSN ESTHAG
- Country of Publication:
- United States
- Language:
- English
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