Development of different types of novel ligands for nuclear waste treatment

Partitioning of actinide (An(III)/lanthanide (Ln(III)) cations is an important step in nuclear waste treatment, which utilizes different types of ligands in different processes. Novel ligands, a sort of hybrids, were prepared by combining essential parts of different well-known classes of ligands, viz. malonamides and glycolamides. However, their extraction behavior turned out to be not as good as that of the original parent ligands. N,N,N',N'-Tetraoctyl-3-oxapentanediamide (TODGA) is currently one of the innovative-SANEX reference compounds due to its high distribution ratios for An(III) and Ln(III) from highly acidic media. TODGA was pre-organized on tripodal and Calix(4)arene platforms and the resulting ligands were evaluated for the extraction of various An(III) cations. The extraction results clearly showed the positive effect of bringing together ligating sites on a molecular platform. Water-soluble TODGA derivatives and tripodal ligands showed interesting back extraction properties. Many nitrogen-donor extractants are known to lose their complexation ability due to protonation of nitrogen under the highly acidic nuclear waste conditions. To possibly overcome this drawback a series of novel pyrazinc-based O,N,O-donor ligands was designed and synthesized, employing a newly developed methodology for palladium-catalyzed phosphorus-carbon coupling of chloropyrazines with various phosphorus pronucleophiles. Several appropriately functionalized pyrazines were grouped together on a Calix arene and their extraction behavior compared with that of the individual pyrazines