Plutonium (IV) complexation by nitrate in acid solutions of ionic strengths from 2 to 19 molal

摘要

Titrations of Pu(IV) with HNO(sub 3) in a series of aqueous HClO(sub 4) solutions ranging in ionic strength from 2 to 19 molal were followed using absorption spectrophotometry. The Pu 5f-5f spectra in the visible and near IR range change with complex formation. At each ionic strength, a series of spectra were obtained by varying nitrate concentration. Each series was deconvoluted into spectra f Pu(sup 4+)(aq), Pu(NO(sub 3))(sup 3+) and Pu(NO(sub 3))(sub 2)(sup 2+) complexes, and simultaneously their formation constants were determined. When corrected for the incomplete dissociation of nitric acid, the ionic strength dependence of each formation constant can be described by two parameters, (beta)(sup 0) and (Delta)(var epsilon) using the formulae of specific ion interaction theory. The difficulties with extending this analysis to higher nitrate coordination numbers are discussed.