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Spectroscopic study on variations in illite surface properties after acid-base titration.
Wen-xin Liu1, R M Coveney, Hong-xiao Tang
1SKLEAC, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. wxliu@urban.pku.edu.cn
Journal of Environmental Sciences (China)
|September 17, 2003
Summary
Acid-base titration alters illite surface properties, forming Al-Si complexes and affecting Si-O and Al-O bonds. These changes indicate structural component dissolution, crucial for understanding aqueous illite surface chemistry.
Area of Science:
- Geochemistry
- Surface Science
- Materials Science
Background:
- Illite, a clay mineral, exhibits complex surface chemistry influenced by acid-base interactions.
- Understanding these interactions is vital for predicting illite behavior in various aqueous environments.
Purpose of the Study:
- To investigate the surface property changes of natural illite following acid-base potentiometric titration.
- To elucidate the mechanisms of structural component dissolution and complex formation on illite surfaces.
Main Methods:
- Fourier-transform infrared (FT-IR) spectroscopy
- Raman microscopy
- X-ray diffraction (XRD)
- 29Si and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy
- Brunauer-Emmett-Teller (BET) surface area analysis
Main Results:
- XRD confirmed surface Al-Si complexes over Al(OH)3 precipitates.
- Raman spectra showed diminished Si-O and Al-O bond vibrations after acid treatment, recovering upon hydroxide titration.
- 27Al MAS NMR revealed changes in (IV)Al and (VI)Al species, indicating participation of edge and basal planes in dissolution.
Conclusions:
- Acid-base titration induces significant changes in illite surface speciation and structure.
- Surface reactions involving silicic acid and aluminum ions are critical for modeling aqueous illite surface properties.