Study on Adsorption of ~(99)Tc on Fe, Fe_2O_3 and Fe_3O_4

The absorption behavior of ~(99)Tc on Fe, Fe_2O_3 and Fe_3O_4 powders from aqueous ~(99)TcO~-_4 (solutions) is studied by batch method in atmospheric conditions. After the adsorption reaches (equilibrium), the valence state of ~(99)Tc in the aqueous solution is examined by extraction with tetraphenylarsonium chloride. The experimental results show that the adsorption ratio of ~(99)Tc on iron powders decreases with the increase of pH (in the range of 5～8) and of CO~(2-)_3 concentration (in the range of 1×10~(-8)～1×10~(-2) mol/L). In opposite, the two factors have no significant influence on the absorption of ~(99)Tc on both Fe_2O_3 and Fe_3O_4 powders. The adsorption isotherms of ~(99)TcO~-_4 on Fe, Fe_2O_3 and Fe_3O_4 powders can be well described by the Freudlich's equation. The major valence state of ~(99)Tc is deduced to be Tc(Ⅳ) when iron powders is used as the absorbent. In the case of Fe_2O_3 or Fe_3O_4 as an absorbent, the ~(99)Tc remains as the TcO~-_4 form.