Solubility and Solubility-Limiting Solid Phase in M(IV)-OH-Dicarboxylate Ternary Aqueous System

Abstract

The solubilities of thorium and zirconium in the presence of several dicarboxylic acids were investigated as functions of the hydrogen ion concentration (pH_c). In the presence of succinic, glutaric, and adipic acids, few Th colloidal species larger than 2 nm were observed, and the apparent solubility appeared to be controlled by thorium-dicarboxylate solid phases. The Th solubility in the presence of fumaric (trans-butenedioic) acid was similar to that in the presence of succinic (butanedioic) acid, whereas no solid phase was observed under pH_c 4 in the presence of maleic (cis-butenedioic) acid. In the presence of succinic and glutaric acids, the contributions of Zr colloidal species to the apparent solubility were observed, possibly due to the stronger hydrolysis reaction than that of Th. The solubility product values of Th and Zr dicarboxylates were determined from the analysis of the solubility data.

KEYWORDS:

• thorium
• zirconium
• solubility
• dicarboxylic acid
• solid phase
• hydrolysis