Complexation of N‐Heterocyclic Substituted 1,10‐Phenanthroline‐2,9‐diamide with Am3+/Eu3+ Ions for Nuclear Waste Water Treatment

Abstract

AbstractDesigning organic ligands is a popular strategy in removing hazardous radioactive substances from nuclear wastewater which has been a major environmental concern. In this regard, a new family of alicyclic substituted 1, 10‐ phenanthroline‐2, 9‐diamide ligands has been reported recently for efficient extraction of Am3+ over Eu3+ ions. Thus, a series of 1, 10‐ phenanthroline‐2, 9‐diamide ligands with heterocyclic substituents (Pyrrolidine, Piperidine, Pyrrole and Dihydropyridine) and their 1 : 1 complexes (ML(NO3)3) have been considered for this investigation to understand the role of substitution of heterocycles in selective extraction process in nuclear waste management. An attempt has been made to unveil the complexation behaviour of these ligands with Am3+ and Eu3+ ions from DFT calculations. Electronic structure, Mulliken Population Analysis, Bond Order Analysis, QTAIM (Quantum Theory of Atoms in Molecules) Analysis, and EDA (Energy Decomposition Analysis) were all performed. We addressed the feasibility of ML(NO3)3 complex formation from thermodynamics perspective where Pyrrolidine moiety has been found to show highest selectivity for Am3+ ion. M−O bonds contribute more to the coordinating ability of the ligands than M−N bonds in each complex, according to the findings. Orbital interactions hold the key between M(NO3)3 and the ligand in stabilizing the complexes. The weak covalent character of Metal‐Ligand bonds is addressed from QTAIM analysis. In short, this study offers guidelines to use heterocycles efficiently to design better ligands for selective partitioning of trivalent Am over Eu ions in the spent nuclear fuel processing.