Experimental results have shown that a mica surface, with aluminum ions adsorbed on it, will remove sulfate ions from very dilute solutions and form stable surface complexes. When the cation sites on the mica were occupied by hydrogen, sodium, or ammonium ions, no adsorption was observed. Hence it was concluded that adsorption in the case of aluminum ions was due to the cation and not to the mica surface itself. An investigation was made into the kinetics of the desorption of S 35-sulfate from an aluminum mica surface. The desorption curves of the S 35-sulfate were obtained and it was found, in all cases, that they could be described as five first-order processes of half-lives 0.02 hour, 0.5 hour, 3.5 hours, 230 hours, and >6 months. These first-order processes had the same half-lives at pH's 1, 3, and 5.