[en] The adsorption mechanism of pertechnetate on activated carbon (AC) has been studied. For this work, the surface of commercial AC was modified using various oxidizing and reducing agents. The changes of surface functional groups were monitored by FT-IR spectroscopy and Boehm titration. The distribution coefficient (K_d) of TcO₄^- on the modified AC has been determined. In acidic media, the value of K_d slightly increased owing to the reductive treatment of ACs, whereas a large decrease in K_d was observed in case of oxidative treatment of ACs. Based on this work, the previous adsorption mechanisms for TcO₄^- on AC were examined. As an alternative adsorption mechanism, the adsorption by electrostatic attraction between TcO₄^- and protonated basic sites on AC surface was proposed. (author)