Chemistry of the CARBEX process. Identification of the absorption bands of the ligands in the electronic spectra of U(VI) extracts with methyltrioctylammonium carbonate

The electronic absorption bands of extracts of the Na 4 [UO 2 (O 2 )(CO 3 ) 2 ] complex with methyltrioctylammonium (MTOA) carbonate were assigned taking into account hydration, hydrolysis, dissociation, polymerization, and ligand exchange, which occur in aqueous and organic solutions. It was shown that the extractable compound, (R 4 N) 4 [UO 2 (O 2 )(CO 3 ) 2 ], present in low concentrations in the organic phase partly dissociates by one step to give the (R 4 N) 3 [UO 2 (O 2 )(CO 3 ) 2 ] – anions, while at high concentrations, it is converted to polynuclear complex.