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Surface complexation model for strontium sorption to amorphous silica and goethite.
Susan A Carroll1, Sarah K Roberts, Louise J Criscenti
1Chemistry, Materials, Earth, and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA. carroll6@llnl.gov
Geochemical Transactions
|January 22, 2008
Summary
Strontium sorption to silica and goethite increases with pH and is influenced by carbonate levels. This study models strontium binding using surface complexation, improving environmental predictions.
Area of Science:
- Environmental Chemistry
- Geochemistry
- Surface Chemistry
Background:
- Understanding strontium sorption is crucial for environmental risk assessment and contaminant transport.
- Amorphous silica and goethite are common soil and mineral phases influencing metal ion behavior.
Purpose of the Study:
- To quantify strontium sorption to amorphous silica and goethite.
- To investigate the influence of pH, strontium, and carbonate concentrations on sorption.
- To develop and refine surface complexation models for strontium.
Main Methods:
- Batch sorption experiments conducted at 25°C.
- Modeling sorption data using the triple layer model and site-occupancy standard state.
- Analysis using extended X-ray absorption fine structure (EXAFS) to determine complexation structure.
Main Results:
- Strontium sorption increased from pH 6 to 10 for both silica and goethite.
- Outer-sphere surface complexes, including mononuclear and binuclear species, were required to model sorption.
- Carbonate presence necessitated additional surface complexation models for goethite.
Conclusions:
- Strontium sorption is pH-dependent and affected by carbonate.
- Outer-sphere complexation accurately describes strontium binding.
- The recalibrated model improves predictions of alkaline earth sorption, but further studies are needed for a comprehensive database.
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