Nickel solubility and precipitation in soils: a thermodynamic study
Issue Date
2006Author
Peltier, Edward
Publisher
Clay Minerals Society
Type
Article
Article Version
Scholarly/refereed, publisher version
Metadata
Show full item recordAbstract
The formation of mixed-metal-Al layered double hydroxide (LDH) phases similar to hydrotalcite has been identified as a significant mechanism for immobilization of trace metals in some environmental systems. These precipitate phases become increasingly stable as they age, and their formation may therefore be an important pathway for sequestration of toxic metals in contaminated soils. However, the lack of thermodynamic data for LDH phases makes it difficult to model their behavior in natural systems. In this work, enthalpies of formation for Ni LDH phases with nitrate and sulfate interlayers were determined and compared to recently published data on carbonate interlayer LDHs. Differences in the identity of the anion interlayer resulted in substantial changes in the enthalpies of formation of the LDH phases, in the order of increasing enthalpy carbonate<sulfate<nitrate. Substitution of silica for carbonate resulted in an even more exothermic enthalpy of formation, confirming that silica substitution increases the stability of LDH precipitates. Both mechanical mixture and solid-solution models could be used to predict the thermodynamic properties of the LDH phases. Modeling results based on these thermodynamic data indicated that the formation of LDH phases on soil mineral substrates decreased Ni solubility compared to Ni(OH)2 over pH 5–9 when soluble Al is present in the soil substrate. Over time, both of these precipitate phases will transform to more stable Ni phyllosilicates.
Description
This is the published version. Copyright 2006 Clay Minerals Society
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Citation
Peltier, Edward, Ramakumar Allada, Alexandra Navrotsky, and Donald L. Sparks. "Nickel Solubility and Precipitation in Soils: A Thermodynamic Study." Clays Clay Miner. Clays and Clay Minerals 54.2 (2006): 153-64. http://dx.doi.org/10.1346/CCMN.2006.0540202
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