Redoxable Deep Eutectic Solvent Boosts Recovery Efficiency of Neptunium

Efficient decontamination and recovery of neptunium (Np) are some of the most challenging tasks in nuclear waste management due to the unique redox nature of Np. A feasible path to fulfill this task is converting inextractable Np-(V) to extractable Np-(IV) or Np-(VI), yet it has not been satisfactorily solved, owing to the inefficient valence conversion. Herein, we report the design and synthesis of a novel redoxable deep eutectic solvent (DES) to realize the in situ reduction of Np-(V) in a biphasic extraction system. With the synergistic effects of complexation by a diglycolamide ligand (hydrogen-bonding acceptor) and reduction by phenol (hydrogen-bonding donor), Np-(V) in the aqueous phase can be effectively reduced to Np-(IV) and extracted into the organic phase, affording a 1000-fold increase in distribution ratios. Meanwhile, the DES is well reusable in a wide range of acidic environments, showing potential in real applications.