Influence of the structure of 2,2’-bipyridyldicarboxamides on stability constants of their complexes with europium and thorium

Abstract

The modern electronic industry requires more and more sources of rare metals, which make attractable newel mineral sources of them. Now the relatively poor ores (as monazite or eudialite) and man-made wastes (as phosphogypsum) are proposed to involve into the rare earth industry. The ores of rare earth elements are often contaminated by natural thorium and/or uranium isotopes. Separation of actinide and lanthanide ions is complicated by their similar ionic radii and chemical properties. To model the separation systems for purification of lanthanides it is important to accurately determine the stability constants of complexes. Also this knowledge gives us the opportunity to understand the nature of metal-ligand interactions. Here we study the reaction of complex formation between metal nitrate hexahydrates M(NO3)n∙6H2O (M: Eu3+ and Th4+, n=3-4) and 2,2’-bipyridine-6,6’-dicarboxamides (R: 2-Me, 2-F, 2-OMe 2,4-diMe) in acetonitrile. Absorption spectra were measured on a Hitachi U-1900 spectrophotometer (at 25°C). Using the spectrophotometric titration method, it was established that in the solution for all metal-ligand pairs, one complex particle with a metal-ligand composition of 1:1 is formed. The stability constants of complexes with f-elements were determined by spectrophotometric titration. The results were processed using the HypSpec2014 program.
This work was supported by RSF, grant No. 21-73-20138.

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Tsagana Sumyanova
Lomonosov Moscow State University
Russia

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