New uranium(VI) complexes with macrocyclic schiff bases and their derivatives

Abstract

An important environmental problem faced by modern radiochemistry is processing of radioactive waste (RW) accumulated both in the manufacture of nuclear weapons and during operation of nuclear power plants. The experience in practical RW processing shows that liquid extraction is the most effective technique for preconcentration, separation, and isolation of radioactive elements. Considerable progress has been achieved in this field in recent years both in Russia and abroad: effective extraction processes for treatment of liquid nitric acid RW with the use of effective chelating agents based on carbamoylmethyl phosphonates (Truex process), malonamides (Diamex process), and other compounds have been developed [1‐3]. However, many countries still store substantial amounts of alkaline RW, which is most difficult to process by extraction. Despite the available data on the extraction of uranium, actinides, lanthanides, and other elements from alkaline solutions [4, 5], the search for effective extractants stable to alkalis is of considerable interest. Several types of polydentate ligands stable in alkaline solutions that selectively bind actinides to form stable complexes are known, in particular, “extended porphyrins” (containing several pyrrole nuclei) [6], macrocyclic Schiff bases (based on pyrrole and polypyrrole derivatives) [7], and salicylidenealdimine derivatives (salens) [8‐11]. However, macrocyclic azomethine I and its reduced analogue II , which we synthesized [12, 13], may prove to be the most promising ligands for actinide preconcentration.