Hyun-Soo Park

Electrolysis of Nitric Acid by Using a Glassy Carbon Fiber Column Electrode System

The electrochemical redox behavior of nitric acid was studied using a glassy carbon fiber column electrode system, and its reaction mechanism was suggested and confirmed in several ways. Electrochemical reactions in less than 2.0M nitric acid was not observed. However, in more than 2.0M nitric acid, the reduction of nitric acid to nitrous acid occurred and the reduction rate was slow so that the nitric acid solution had to be in contact with an electrode for a period of time long enough for an apparent reduction current of nitric acid to nitrous acid to be observed. The nitrous acid generated in more than 2.0M nitric acid was rapidly and easily reduced to nitric oxide by an autocatalytic reaction. Sulfamic acid was confirmed to be effective to destroy the nitrous acid. At least 0.05M sulfamic acid was necessary to scavenge the nitrous acid generated in 3.5M nitric acid.

Removal of Residual Uranium in Simulated Radwaste Solution by TBP Extraction

The extraction behavior of uranium in a multicomponent system simulated on the basis of high-level liquid waste was examined in order to find effective conditions for the removal of residual uranium in a simulated radwaste solution by the TBP solvent extraction method. While the conventional semiempirical equation for the distribution coefficient of uranium could be used in a system composed of only uranium and nitric acid, it was found to be unsuitable for a multicomponent system where the concentration of uranium is not dominant. Uranium extractability by TBP was found to be limited in multicomponents systems regardless of high TBP concentration, phase ratio, and extraction times because of the presence of neodymium and iron together with uranium in the systems.

A Study on Development of an Electrolysis System with Vertically Circulating Mercury Capillary Bundle Electrode and Its Characteristics

An electrolysis system with a vertically circulating mercury capillary bundle electrode was developed with a very large electrode area in a minimum space by force feeding mercury and an aqueous solution containing metal ion into a fiber bundle packed densely within a small porous glass tube. In order to test the characteristics and stability of the electrolysis system, the reduction voltammograms of uranyl and ferric ions were measured with changes in the mercury and aqueous flow rates. The aqueous flow rate had a large effect on the electroreaction of the metal ion occurring on the interface between the mercury and the aqueous solution and had to be regulated at an appropriate value for the good development of limiting current shape. The limiting current is linearly proportional to the aqueous flow rate. With a mercury flow rate high enough to keep a capillary continuum of mercury in the fiber bundle, the mercury flow rate had almost no effect on the electroreaction. This developed system was confirmed to be effective and stable enough to control rapidly and continuously the oxidation state of metal ions fed into the system under an appropriate aqueous flow rate, having the property of a high overpotential against the hydrogen evolution reaction.