Theoretical Insights into the Separation of Am(III)/Eu(III) by Hydrophilic Sulfonated Ligands

Carbon NMR Titration Could Be More Informative for In-Situ Lanthanide Coordination Chemistry Investigation

In situ characterization of coordination species and their evolution are crucial for effective lanthanide separation and recycling. Current technical approaches often operate under constrained conditions, requiring complex equipment, experimental setups, and sometimes intricate data interpretation. Herein, we demonstrate that carbon NMR titrations offer a valuable approach for in situ coordination analysis of lanthanides, particularly for highly fused preorganized ligands that offer more NMR-active carbons than traditional proton NMR. Two representative ligands of both lipophilic and hydrophilic in nature were investigated, and the resulting carbon NMR titration data were analyzed. Comparisons with IR and single-crystal data showed that NMR provided insights not only into the evolution of coordination species but also into changes in the electron distribution during complex formation. Additionally, we discussed inconsistencies between atomic charge populations obtained from carbon NMR and those from Mulliken and Hirshfeld calculations. With advancements in NMR technology and the availability of higher-field NMR instruments, we believe NMR titrations will play an increasingly significant role in unravelling the complex solution coordination chemistry of f-block elements.

Accessing renewable magnetic cellulose nanofiber adsorbent to enhance separation efficiency for adsorption and recovery of Cd2

To address the issue of toxic cadmium pollution and meet the need for rapid separation from water body, a magnetic bio-composite material, marked as CFeMg, was prepared via a facile method. It explicitly includes components of cellulose nanofiber (CNF), Fe3O4 and Mg (OH)2. The microstructures and morphology were characterized and analyzed using XRD, FT-IR, SEM, and TEM. CNF was chemically coupled by Fe3O4, which together constructed the overall layered structure. Between layers were Mg(OH)2 flakes attached. While dealing with Cd2+, qmax of the best sample reached 361.5 mg g-1 with high adsorption efficiency. The roles of three components were explored and the adsorption mechanism was proposed. Assisted by magnetic CNF, it only took 3 min to efficiently and completely salvage the spent CFeMg sample from water after adsorption. Due to its high adsorption capacity and facile recovery performance, the prepared composite has promising application as water treatment.

Theoretical Insights into the Selectivity of Hydrophilic Sulfonated and Phosphorylated Ligands to Am(III) and Eu(III) Ions

The separation of lanthanides and actinides has attracted great attention in spent nuclear fuel reprocessing up to date. In addition, liquid-liquid extraction is a feasible and useful way to separate An(III) from Ln(III) based on their relative solubilities in two different immiscible liquids. The hydrophilic bipyridine- and phenanthroline-based nitrogen-chelating ligands show excellent performance in separation of Am(III) and Eu(III) as reported previously. To profoundly explore the separation mechanism, herein, we first of all designed four hydrophilic sulfonated and phosphorylated ligands L¹, L², L³, and L⁴ based on the bipyridine and phenanthroline backbones. In addition, we studied the structures of these ligands and their neutral complexes [ML(NO₃)₃] (M = Am, Eu) as well as the thermodynamic properties of complexing reactions through the scalar relativistic density functional theory. According to the changes of the Gibbs free energy for the back-extraction reactions, the phenanthroline-based ligands L² and L⁴ have stronger complexing capacity for both Am(III) and Eu(III) ions while the phosphorylated ligand L³ with the bipyridine framework has the highest Am(III)/Eu(III) selectivity. In addition, the charge decomposition analysis revealed a higher degree of charge transfer from the ligand to Am(III), suggesting stronger donor-acceptor interactions in the Am(III) complexes. This study can provide theoretical insights into the separation of actinide(III)/lanthanide(III) using hydrophilic sulfonated and phosphorylated N-donor ligands.

Theoretical Insights into the Selective Separation of Am(III)/Eu(III) Using Hydrophilic Triazolyl-Based Ligands

Designing ligands with efficient actinide (An(III))/lanthanide (Ln(III)) separation performance is still one of the key issues for the disposal of accumulated radioactive waste and the recovery of minor actinides. Recently, the hydrophilic ligands as promising extractants in the innovative Selective ActiNide Extraction (i-SANEX) process show excellent selectivity for Am(III) over Eu(III), such as hydroxylated-based ligands. In this work, we investigated the selective back-extraction toward Am(III) over Eu(III) with three hydrophilic hydroxylated triazolyl-based ligands (the skeleton of pyridine L^a, bipyridine L^b, and phenanthroline L^c) using scalar-relativistic density functional theory. The properties of three hydrophilic hydroxylated ligands and the coordination structures, bonding nature, and thermodynamic properties of the Am(III) and Eu(III) complexes with three ligands have been evaluated using multiple theoretical methods. The results of molecular orbitals (MOs), quantum theory of atoms in molecules (QTAIMs), and natural bond orbital (NBO) reveal that Am-N bonds possess more covalent character compared to Eu-N bonds. The thermodynamic results indicate that the complexing ability of L^b and L^c with metal ions is almost the same, which is stronger than that of L^a. However, L^a has the best Am(III)/Eu(III) selectivity among three ligands, which is attributed to the largest difference in covalency between Am-N_trzl and Eu-N_trzl bonds in ML^a(NO₃)₃. This work provides an in-depth understanding of the preferential selectivity of the hydrophilic hydroxylated ligands with An(III) over Ln(III) and also provides theoretical support for designing potential hydrophilic ligands with excellent separation performance of Am(III)/Eu(III).

Theoretical insights into the separation of Am(iii)/Eu(iii): designing ligands based on a preorganization strategy

The extraction behaviors of Am(iii) and Eu(iii) were investigated using phenanthroline and bipyridine ligands based on a preorganization strategy.