Electrochemical Behavior Of Fission Product Palladium In Acid And Ionic Liquid Solutions

Spent nuclear fuel is composed of artificial noble metals such as Palladium(Pd), Ruthenium(Ru) and Rhodium(Rh) and so on. As a result, for the separation of Uranium(U) and Plutonium(Pu) from the spent nuclear fuel dissolver solution PUREX process was introduced to solve the problem. The nitric acid raffinate obtained after extraction is called ―High-Level Liquid Waste‖ also known as HLLW. There are large quantities of valuable noble metals in HLLW. Further more, most of the isotopes of PMGs(short for platinum group metals) formed from fission reaction are weakly radioactive or not radioactive, so many industrial applications can tolerate this kind of radioactive materials. Pd metal is a well-known noble metal, which has important position in many industrial applications. Palladium nanoparticles have received increasing attention in recent years, mainly because of their unique properties such as high catalytic activity toward electrooxidation of ethanol, methanol, formic acid, formaldehyde and polycyclic aromatic hydrocarbons. The nature abundance of PGMs is quite low and the PGMs in the mineral would be consumed up in decades. On the other hand, PGMs in spent nuclear fuel increases the melting point of waste glass formed and tends to separate as distinct phase during vitrification leading to a non-homogeneous glass matrix. As a result, there is an increasing interest to recover PGMs from spent fuel.In this work, the electrochemical behaviors of palladium in hydrochloric acid solution and ionic liquid solution were studied utilising different kinds of electrochemical methods and UV-vis. Palladium electrodeposition behavior was studied utilizing potentiostatic current–time transients, cyclic voltammetryand Tafel curve methods. By means of CCTs, the regions corresponding to the mixed control, charge transfer control and diffusion control were recognised. Palladium electrodeposition mechanism was described as 3D progressive nucleation growth under diffusion control. It is easier for palladium to electrodeposite in ionic liquid solution than that in hydrochloric acid solution and the distribution of palladium nanoparticle is more homogenous. At the same time, the electrochemical behavior of Rh in [EMIm]NTf2 ionic liquid solution was also researched. It turns out that it is possible to electrodeposite Pd and Rh separately in [EMIm]NTf2 ionic liquid solution.