Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with
the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring
ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (
–polyacrylate. By using the stability data obtained for all the complex species formed, the uranium(VI) sequestration by PAA
and FA was expressed by the pL50 parameter [i.e. the −log(total ligand concentration) necessary to bind 50% of uranyl ion] at different pH values. A comparison
between pL50 values of FA and PAA and some low molecular weight carboxylic ligands toward uranyl ion is also given.