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

Abstract

Protactinium complexation with sulfate ions was studied with the element at tracer scale ( C Pa ∼ 10 −12 M) by solvent extraction method. The involved aqueous system was Pa(V)/H 2O/HClO 4/Na 2SO 4/NaClO 4 at 10 and 60 °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 ( β 1, β 2 and β 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 β 1 0 , log β 2 0 , log β 3 0 of 2.8 ± 0.5, 6.5 ± 0.5, 7.8 ± 0.5 at 10 °C and 4.3 ± 0.3, 8.4 ± 1.3, 9.6 ± 0.4 at 60 °C. Interaction coefficients involving the sulfate complexes of protactinium(V) were also derived.