Separation and Remediation of 99TcO4– from Aqueous Solutions

Technetium-99 (99Tc) is one of the most-problematic radioisotopes in used nuclear fuel owing to its intrinsic features of a high fission yield, long half-life, high environmental mobility, volatile nature during waste vitrification, and its redox interface capability with actinides during used fuel repossessing. The selective separation of pertechnetate (TcO4–) from legacy nuclear waste and contaminated natural water is therefore highly desirable but still a significant challenge, because the conditions of a strong radiation field, high ionic strength, high acidity/alkalinity, and large amounts of competing anions are often involved in these systems. Until now, there are a handful of functional materials that can efficiently remove TcO4– from nuclear waste solutions with high uptake capacities, fast kinetics, and good selectivity, but room still remains to further improve our capabilities for controlling the contamination/separation of TcO4–. In this Perspective, we discuss the current state of the art TcO4– separation materials including precipitation agents, reducing materials, ion-exchange resins, inorganic cationic frameworks, cationic metal–organic frameworks (MOFs), and cationic polymeric networks (CPNs) materials. The intriguing separation mechanisms of these materials for TcO4– are also disclosed, which may hopefully shed light on further development in this field.