A Continuous Denitration Process Combining Chemical and Electrolytic Systems for the Destruction of High Concentration of Nitric Acid (I)

摘要

This work has imporved the conventional batch denitration by formic acid which has been used for controlling the acidity of solution for the solvent extractions to partition the long lived-radionuclides from the high level radioactive liquid waste.The characteristics of destructions of nitric acid and formic acid and their destructive products in a continuous denitration process combining a continuous denitration system by formic acid and an electrolytic residual acid-trimming system suggest in this work was evaluated.The continuous denitration by formic acid reached a steady state in 30 minutes and showed the dependence of the final acidity on the residence time of feeding solution into the reactor.Alao the system had the lowest final acidity at a mole ratio of formic acid to nitric acid of 1.5 like the batch denitration.In a Ti-IrO_2 electrolytic cell,the destructive rates of formic acid and nitric acid were 9.33X10~(-3) and 10~(-2) M/(hr·mA/cm~2),respectively.The nitric acid and the fromic acid were destructed through the reduction at the Ti cathode and the oxidation at the IrO_2 anode,respectively.The newly suggested continuous denitration process combining the denitration by formic acid and residual acid-electrolytic treatment could control continuously a feeding nitric acid of 2.0 M to below about 0.1 M.