Radiolytic and Chemical Degradation of Strong Acidic Ion-Exchange Resins: Study of the Ligands Formed

Abstract

The formation of water-soluble organic ligands by radiolytic and chemical degradation of several strong acidic ion-exchange resins was investigated under conditions close to those of the near field of a cementitious repository. The most important degradation products were studied and their complexing properties evaluated.

Irradiation of strong acidic cation exchange resins (Powdex PCH and Lewatite S-100) resulted in the formation of mainly sulfate and dissolved organic carbon. High-performance liquid chromatography analysis indicated the presence of oxalate, contributing to 10 to 20% of the organic carbon. The identity of the remainder is unknown. The presence of oxalate as a complexant is consistent with results from earlier work. Complexation studies with Cu²⁺ and Ni²⁺ showed the presence of two ligands: oxalate and ligand X. Although ligand X could not be identified, it could be characterized by its concentration ([X]_T ~ 10^-5 to 10^-6 M), a deprotonation constant (pK_H ~ 7.4 at I = 0.1 M), and a complexation constant for the NiX complex (log K_NiX ~ 7.0 at I = 0.1 M).

In the absence of irradiation, no evidence for the formation of ligands was found.