Solvent extraction of americium by imidodiphosphates and diimidotriphosphates

Solvent extraction was described for determining of the americium content in the liquid samples. Arylesters of imidodiphosphoric, imidothiodiphosphoric, imidodithiodiphosphoric acids and tetraphenylimidodithiodiphosphine are used as representatives of bidentate organophosphoric extractants. From the group of tridentate agents, pentaphenyldiimidotriphosphate, was used. The extraction properties of tetraphenyl imidodiphosphates and their sulphur analogues for trivalent americium in 0.1 mol L⁻¹ HNO₃ into toluene also in the presence of tri-n-octylphosphine oxide (TOPO) were investigated. The dependences of equilibrium ratios of the americium on analytical or equilibrium concentration of chelating agents, pH, initial concentration of nitric acid and initial concentration of TOPO were studied. The structures of the complexes in the organic phase were determined and the values of extraction constants were calculated. The extracted species were AmA₃, AmA₃ (HA), the addition of TOPO induced synergistic extraction of AmA₃ TOPO. The utilization of sulphur analogues was marginal.