The coordination mechanism of carboxylic acid ligands with metal ions in nuclear waste solution

Nd is an element in the reprocessing solution of nuclear fuel. Studying the complexation behavior of different ligands coordination with lanthanides not only helpful to understand the basic chemical behavior of lanthanides, but also contribute to the design and application of lanthanide separation ligands. In this paper, the coordination behavior of N,N-dimethyl-6-tert-amine-2-carboxy pyridine (DMPA) and N, N-dialkyl-6-amide-pyridine-2-carboxy-pyridine (DMAPA) with Nd(III) in aqueous solution were studied. Nd(III) and DMPA can form 1:1,1:2,1:3 complex species by spectrometric titration. The stability constants of DMPA and Nd(III) complex were determined. Compared with similar ligand DMAPA, it was found that the complexation ability of amide group with Nd(III) was greater than that of tertiary amine under the same conditions. 1-2/Nd-DMPA crystals were crystallized in aqueous solution. Through crystal structure analysis and bond length and bond Angle comparison, it was found that the bond length between carboxylic acid O atom and Nd(III) was the shortest, while the bond length between trimethylamine N atom and Nd(III) was longest, which indicated that the coordination ability of trimethylamine and Nd(III) was weak.