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Modeling tetracycline antibiotic sorption to clays
Raquel A Figueroa1, Allison Leonard, Allison A MacKay
1Environmental Engineering Program, University of Connecticut, 261 Glenbrook Road, U-2037, Storrs, Connecticut 06269-2037, USA.
Environmental Science & Technology
|January 31, 2004
Summary
Tetracycline antibiotics sorbed to clays via cation exchange and surface complexation. Sorption depended on pH and clay type, suggesting models must consider speciation and competing ions in soil.
Area of Science:
- Environmental Chemistry
- Soil Science
- Clay Mineralogy
Background:
- Tetracycline antibiotics are widely used and frequently detected in the environment.
- Understanding their sorption behavior in soils and sediments is crucial for environmental risk assessment.
Purpose of the Study:
- To investigate the sorption interactions of three major tetracycline antibiotics with montmorillonite and kaolinite clays.
- To evaluate the influence of pH and ionic strength on these sorption processes.
Main Methods:
- Sorption experiments were conducted under varied pH and ionic strength conditions.
- Sorption data were analyzed using models incorporating cation exchange and surface complexation.
- The role of zwitterion forms and calcium bridging was examined.
Main Results:
- Sorption was best described by a model including cation exchange and surface complexation of zwitterion forms.
- Zwitterion sorption involved proton uptake, favored acidic clays, and was insensitive to ionic strength.
- Calcium salts enhanced sorption at alkaline pH via surface bridging.
- Montmorillonite showed greater sorption than kaolinite, even after normalizing for cation exchange capacity.
Conclusions:
- Sorption mechanisms involve cation exchange and surface complexation of zwitterions.
- Environmental models for tetracyclines must account for solution speciation and competing ions.
- Clay type significantly influences tetracycline sorption behavior.