^(99)Tc在Fe,Fe_2O_3和Fe_3O_4上的吸附行为研究

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

用批式法研究了大气条件下99Tc在Fe,Fe2O3和Fe3O4上的吸附行为,考察了吸附平衡后溶液中99Tc的存在价态。实验结果表明:随着溶液pH值(5～12)、CO2-3浓度(1×10-8～1×10-2mol/L)的增大,99Tc在Fe上的吸附比减小;溶液pH值、CO2-3浓度的变化基本不影响99Tc在Fe2O3和Fe3O4上的吸附;99Tc在这3种吸附材料上的吸附行为均可用Freundlich吸附等温式表示;当Fe作吸附材料时,吸附平衡后99Tc主要以Tc(Ⅳ)的形式被吸附,当Fe2O3和Fe3O4作为吸附材料时,99Tc主要以Tc(Ⅶ)的形式被吸附。

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.