Complex formation between protactinium(V) and sulfate ions at 10 and 60 °C

Protactinium complexation with sulfate ions was studied with the element at tracer scale (C-Pa similar to 10 (12) M) by solvent extraction method. The involved aqueous system was Pa(V)/H2O/HClO4/Na2SO4/NaClO4 at 10 and 60 degrees C. The extraction experiments were conducted using the chelating agent thenoyltrifluoroacetone (TTA) in toluene. For both values of temperature, a systematic study was performed in order to determine the formation constants (beta(1), beta(2) and beta(3)) of sulfate complexes of Pa(V) at different ionic strength. For each temperature, the extrapolation of these constants to zero ionic strength was performed using the Specific Interaction Theory, leading to values log beta(0)(1); log beta(0)(2); log beta(0)(3) of 2.8 +/- 0.5, 6.5 +/- 0.5, 7.8 +/- 0.5 at 10 degrees C and 4.3 +/- 0.3, 8.4 +/- 1.3, 9.6 +/- 0.4 at 60 degrees C. Interaction coefficients involving the sulfate complexes of protactinium(V) were also derived. (C) 2009 Elsevier B. V. All rights reserved.