Mechanisms of Aluminum Adsorption on Clay Minerals and Peat
1985
Jardine, P. M. | Zelazny, L. W. | Parker, J. C.
Mechanisms of Al adsorption on Ca-saturated kaolinite, montmorillonite, and peat were studied by miscible displacement methods. Partially neutralized 1.0 × 10⁻⁴ M AlCl₃ solutions with basicities of 1.0 were leached through monomineralic columns and effluent analyzed for monomeric and polymeric Al, titratable acidity, and desorbed Ca as functions of time. Polymeric Al was preferentially adsorbed by kaolinite throughout the displacement experiment whereas montmorillonite preferentially adsorbed monomers at short times and polymers at longer times. Selective adsorption of monomeric or polymeric Al on peat was not evident. Aluminum adsorption kinetics on kaolinite, montmorillonite, and peat was described by two simultaneous reactions—a relatively rapid reaction involving Al-Ca exchange and a slower reaction involving Al polymerization on the adsorbents. This scenario is supported by potentiometric titrations of effluent Al and by analyses of effluent Ca, and adsorbed, exchangeable and nonexchangeable Al basicities. Negligible adsorption of Al on gibbsite and quartz indicated that surface bound Al on kaolinite and montmorillonite may serve as a template for adsorption of more Al.
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