It is demonstrated that the radiotracer technique offers a unique tool to distinguish easily specific and electrostatic adsorption of some anions at the gamma- Al2O3 surface in acid media. The specific adsorption of sulfate and the electrostatic adsorption of pertechnetate ions were compared. It is shown that the study of the adsorption of TcO4- ions may serve as a tool for the investigation of the behavior of the double layer formed at Al2O3 in acidic media.