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Kinetics and mechanisms of Al adsorption on Ca-saturated kaolinite, montmorillonite, and peat were studied using miscible displacement methods. Unneutralized and partially neutralized Al solutions (OH/Al=1.0) were leached through monomineralic columns and effluent analyzed for monomeric and polymeric Al, titratable acidity, and desorbed Ca as a function of time. Observed breakthrough curves (BTC) for continuous injection of the various Al solutions through kaolinite suggested the existence of at least two mechanisms for Al adsorption. It was shown that a relatively rapid reaction, where solution Al was in equilibrium with the solid phase, involved Ca-Al exchange and a slower reaction involved Al polymerization on the adsorbent. This scenario was supported by rigorous modeling of observed BTC with nonequilibrium transport theory, analysis of desorbed Ca effluent, and potentiometric titrations of effluent solutions. The occurrence of two mechanisms for Al adsorption on montmorillonite and peat was also evident. 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 either form of Al on peat was not evident. In order to accurately distinguish between monomeric and polymeric Al in solution and on solids, a method was developed which evaluates the interaction of ferron with Al. The colorimetric complexation of aqueous Al with ferron was largely described by a binary species first-order rate function. Based on the differential kinetic reactions of ferron with monomeric and polymeric Al, the fraction of the former species was well predicted using the binary species model. The method avoids arbitrary separation times for the distinction of monomeric and polymeric Al since the duration of monomer interactions with ferron depend on the initial basicity of the Al solution. / Ph. D.