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Mercury binding sites in thiol-functionalized mesostructured silica.
Simon J L Billinge1, Emily J McKimmy, Mouath Shatnawi
1Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA.
Journal of the American Chemical Society
|June 9, 2005
Summary
Thiol-functionalized silica effectively removes mercury from water. Research reveals mercury binds to sulfur, forming clusters and changing coordination with increasing mercury levels.
Area of Science:
- Materials Science
- Environmental Chemistry
- Nanotechnology
Background:
- Thiol-functionalized mesoporous silica demonstrates potential for heavy metal remediation.
- Understanding the mercury-binding mechanism is crucial for optimizing removal efficiency.
Purpose of the Study:
- To elucidate the mercury-binding mechanism in thiol-functionalized mesostructured silica.
- To investigate the structural and chemical changes upon mercury adsorption.
Main Methods:
- Synchrotron X-ray powder diffraction with atomic pair distribution function (PDF) analysis.
- Raman spectroscopy.
- Synthesis of thiol-functionalized mesoporous silica with varying functionalization levels (x=0.30, 0.50).
Main Results:
- Evidence of bridging thiolate sulfur atoms to mercury ions, forming surface chains.
- No significant Hg-O bonds detected, ruling out oxygen coordination.
- Mercury centers cluster via thiolate bridging, independent of loading.
- Mercury complexation changes from neutral (tetrahedral coordination) at low loading to cationic (linear coordination) at high loading, with nitrate as a counter-anion.
Conclusions:
- Thiol-functionalized silica binds mercury primarily through sulfur coordination.
- The binding mechanism and mercury speciation are dependent on the mercury loading.
- These findings provide insights for designing advanced sorbents for mercury removal.
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