Electrochemical Studies on Uranium in the Presence of Organic Acids

Abstract

We examined electrochemical redox reactions of UO2 2+ in perchlorate and organic acid (oxalic, malonic, succinic, adipic, L-malic, and L-tartaric acids) solutions using cyclic voltammetry to reveal the effects of complex formation with organic acids on the redox behavior. In the perchlorate and organic acid solutions, a redox reaction of UO2 2+/UO2 + and an oxidation reaction of U(IV) produced by a disproportionation of UO2 + were observed. The peak potentials of the UO2 2+ reduction showed a good linear relationship with the stability constants of 1:1 UO2 2+-organic complexes. In the presence of malonic acid, the redox potential for UO2 2+/UO2 + was constant at pH 1-2 and 5-6 while it decreased with an increase in pH from 2 to 5. Additionally, it was independent of malonate concentration at 0.1–0.5 M while it decreased with an increase in the concentration from 0.005 to 0.1 M. Based on the experimental and the speciation calculation results, we determined the redox reactions of UO2 2+-malonate complexes as a function of pH and malonate concentration. We also determined the redox reactions of UO2 2+-oxalate complexes in the same way.