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MODELING THE ADSORPTION OF ORGANIC DYE MOLECULES TO KAOLINITE

Rodney G. Harris, John D. Wells^*, Michael J. Angove and Bruce B. Johnson

Colloid and Environmental Chemistry Laboratory, La Trobe University, PO Box 199, Bendigo, Victoria 3552, Australia

^* E-mail address of corresponding author: j.wells{at}latrobe.edu.au

Simple extended constant capacitance surface complexation models have been developed to represent the adsorption of polyaromatic dyes (9-aminoacridine, 3,6-diaminoacridine, azure A and safranin O) to kaolinite, and the competitive adsorption of the dyes with Cd. The formulation of the models was based on data from recent publications, including quantitative adsorption measurements over a range of conditions (varying pH and concentration), acid-base titrations and attenuated total reflectance-Fourier transform infrared spectroscopic data. In the models the dye molecules adsorb as aggregates of three or four, forming outer-sphere complexes with sites on the silica face of kaolinite. Both electrostatic and hydrophobic interactions are implicated in the adsorption processes. Despite their simplicity, the models fit a wide range of experimental data, thereby supporting the underlying hypothesis that the flat, hydrophobic, but slightly charged silica faces of kaolinite facilitate the aggregation and adsorption of the flat, aromatic, cationic dye molecules.

Key Words: 9-aminoacridine • 3,6-diaminoacridine • Azure A • Dye • Hydrophobic Interactions • Kaolin • Safranin O • Surface Complexation Models

This article has been cited by other articles:

				R. G. Harris, B. B. Johnson, and J. D. Wells STUDIES ON THE ADSORPTION OF DYES TO KAOLINITE Clays and Clay Minerals, August 1, 2006; 54(4): 435 - 448. [Abstract] [Full Text] [PDF]

				R. G. Harris, B. B. Johnson, and J. D. Wells COMPETITIVE ADSORPTION OF Cd AND DYES TO KAOLINITE Clays and Clay Minerals, August 1, 2006; 54(4): 449 - 455. [Abstract] [Full Text] [PDF]