Reaction of Nitrate Ion With Formic Acid in the Presence of Uranium

The reaction of nitric acid with formic acid, including uranium-containing solutions, was studied. Empirical equations for the dependence of the induction period duration (τ) on the concentrations of reagents and temperature were determined. The dependence of τ on the concentration of formic acid is exponential. The effect of uranium concentration on τ in denitrated solutions becomes noticeable only at temperatures lower than 60°C. The main factor affecting the completeness of denitration is the molar ratio [formic acid] : [NO]. Starting with the molar ratio of >3, uranium-containing solutions are denitrated at 90°C in an hour almost quantitatively. The resulting uranyl formate is partially precipitated. The initial stage of the reaction is accompanied by violent gas evolution. At 90°C, ~80% of the gas volume is released at this stage (about 10 s), whereas at 40°C, only ~10%.