A functionalized ionic compound for the extraction of ReO₄^-/TcO₄^- from highly acidic environment

Selective extraction of TcO4- from high-level liquid waste (HLLW) is essential for spent fuel reprocessing but most of the available extractants can't effectively extract TcO4- from highly acidic environment. In this manuscript, a functionalized ionic compound (I-TPyam) that contains the amide group was synthesized, which can efficiently extract ReO4- from highly acidic environment. 0.3 M I-TPyam solution can extract 97.3 % and 88.0 % of ReO4- from ReO4- solutions that contains 1 M and 3 M nitric acid. Even in more realistic simulated HLLW that contains 22 metal ions and 2.5 M HNO3, it can still extract 87.0 % of the Re. This performance can be further improved by two-stage extraction or denitration treatment, with extraction efficiency increased to 94.9 % and 96.4 %, respectively. Besides, this extractant can also effectively extract Re from neutral ReO4- solution and simulated LAW, with distribution ratio reached 10,468 and 246, respectively. A small portion of Mo will be co-extracted but can be selectively stripped in the stripping process. Our XPS experiments, along with DFT simulations high-lighted the predominate role of pyridinium and amide groups in Re (Tc) extraction, revealed the driving forces and explained why I-TPyam prefer to extract ReO4- instead of NO3-