Sorption properties of clinoptilolite tuff modified by Fe-containing solutions were studied. The absence of sorption of monocharged anions at any pH of the solution and a high sorption capacity (up to 2.0 to 2.5 mg-eq g(-1)) for phosphate ions at pH 10 to 11.5 were shown. Desorption of phosphates by solutions of salts and mineral acids was studied.