Stability Constants of Np(V) Complexes with Phosphate at Variable Temperatures

May 4, 2006

Conference Paper

Stability Constants of Np(V) Complexes with Phosphate at Variable Temperatures

Abstract

A solvent extraction method was used to determine the stability constants of Np(V) complexes with phosphate in 1.0 M NaClO4 from 25o C to 55o C. A morpholine-4-ethanesulfonic acid buffer was used to maintain pH at about 5 in the Np(V)-H2PO4- system. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of phosphate were increased. Stability constants of the 1:1 Np(V)-H2PO4- complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [H2PO4-] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures by using the Van’t Hoff equation.

Revised: February 17, 2009 | Published: May 4, 2006

Citation

Xia Y., J.I. Friese, D.A. Moore, and L. Rao. 2006. Stability Constants of Np(V) Complexes with Phosphate at Variable Temperatures. In 2006 International High Level Radioactive Waste Management Conference, 716-721. La Grange Park, Illinois:American Nuclear Society. PNNL-SA-48528.