Nitric acid effect on oxalate destruction with and without catalyst

The oxalate supernatant generated in CORAL contains 40-60 mg/L of Pu, 3-5 g/L of U, 0.1– 0.15 M oxalate ion in 2.5-3.5 M nitric acid. The presence of oxalate ion in the supernatant can hinder the recovery of plutonium in the subsequent processing step. Therefore this is a need to remove or destroy the oxalate ion present in the supernatant before processing. The destruction of oxalate ion using Mn²⁺ catalyzed nitric acid process at higher temperature was studied in our laboratory. For understanding the process the effect of nitric acid on oxalate destruction was studied in the presence and absence of Mn²⁺ catalyst. The mechanism involves the oxidation of oxalate ion to CO₂ by nitric acid. Therefore, the rate of destruction of oxalate ion increases with increase in the case of nitric acid. Combined effect of catalyst and nitric acid on the rate of destruction of oxalate ion. This trend indicates some kind of catalytic retardation at higher acidity. The catalytic retardation probably could be attributed to the formation of low spin stable Mn(II)- NO complex at higher HNO₃ concentration, which decrease the availability of Mn²⁺ ion for the reaction with the oxalate ion, inhibiting the destruction