Ultraselective Extraction Reprocessing of ⁹⁹TcO₄^-/ReO₄^- with a Promising Carbamic Acid Extractant System

With the development of nuclear energy, the reprocessing of ⁹⁹TcO₄^-/ReO₄^- has become a very difficult problem due to environmental issues such as high output, long life, and easy leakage. In this study, three extraction systems containing carbamic acid were introduced into the reprocessing of ⁹⁹TcO₄^-/ReO₄^- for the first time. The results involving one of the three results show that N-[N,N-di(2-ethylhexyl) aminocarbonylmethyl] glycine (D2EHAG) has ultrahigh selectivity for removal to ⁹⁹TcO₄^-/ReO₄^-. When the extreme concentration ratio of SO₄^2- and Cl^- to ReO₄^- of D2EHAG is 10,000:1, the distribution coefficient of ReO₄^- still reaches 12.73 and 2.67, respectively. Additionally, the most hydrophilic NO₃^-, when the extreme concentration ratio of NO₃^- and ReO₄^- is 1000:1, still has a distribution coefficient close to 2.33, which is more than the most reported MOF adsorption materials. Moreover, the reaction kinetics, stripping rate, and reuse rate were studied. After five cycles, the removal rate is still 98.12%, with a decrease of less than 0.7%. The system containing carbamic acid is a potential extraction removal system to remove ⁹⁹TcO₄^-/ReO₄^- from nuclear radioactive wastewater.