Successful Decontamination of 99TcO4‐ in Groundwater at Legacy Nuclear Sites by a Cationic Metal‐Organic Framework with Hydrophobic Pockets

99Tc contamination at legacy nuclear sites is one of the most serious and yet unsolved environmental issues associated with nuclear power development. Selective remediation of 99TcO4‐ in the presence of large excess of NO3‐ and SO42‐ from natural waste systems represents a significant scientific and technical challenge given anions with higher charge density are often preferentially sorbed by traditional anion‐exchange materials, which is known as the Hofmeister Bias selectivity. We report here a solution to this challenge based on a stable three‐dimensional cationic metal‐organic framework material, SCU‐102 (Ni2(tipm)3(NO3)4), formed by hydrophobic tetradentate neutral ligands and Ni2+ ions. SCU‐102 exhibits fast sorption kinetics, large capacity (291 mg/g), high distribution coefficient and, most importantly, the record high TcO4‐ uptake selectivity among all anion‐exchange materials reported to date. This material can almost quantitatively remove TcO4‐ in the presence of large access of NO3‐ and SO42‐. The decontamination experiments based on both a simulated low activity waste stream, and contaminated groundwater at the Hanford site confirm that SCU‐102 represents the optimal Tc scavenger with the highest clean up efficiency. First principle simulation reveals that the origin of the exceptional selectivity is the recognition of TcO4‐ by the abundant hydrophobic pockets in the structure.

from A via a.sfakia on Inoreader http://bit.ly/2GqOKu5