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

Abstract

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 highlighted 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−.