Hydrolysis of Protactinium(V). I. Equilibrium Constants at 25°C: A Solvent Extraction Study with TTA in the Aqueous System Pa(V)/H2O/H+/Na+/ClO4 −

The hydrolysis of protactinium(V) was studied at tracer scale (ca. 10^–12 M) with the solvent extraction method involving the aqueous system: Pa(V)/H₂O/H⁺/Na⁺/ClO₄ ^– at 25.0°C for three values of ionic strength. Extraction experiments were conducted using the chelating agent thenoyltrifluoroacetone (TTA) in toluene. Hydrolysis constants are reported for each ionic strength investigated. An SIT modeling is presented and extrapolated constants to zero ionic strength are derived, as well as interaction coefficients of the two hydrolyzed species involved.