Electrochemical Behavior Of Uranium In Ionic Liquids

Nuclear energy is the only reasonable alternative to theenvironent-unfriendly energy production based on fossil fuels. Because ofincreasing burn up of power reactor and shortening the cooling time moreadvanced technologies should be applied in the reprocessing of spentnuclear fuel, as well as coming of the spent fast reactor fuels and ADStransmutation fuels. The dry reprocessing was widely considered as themost promising menthod for deal with the spent nuclear fuels. Due totheir unique physical and chemical properties, room temperature ionicliquids have recently received an ever-increasing amount of interest innuclear fuel reprocessing, especially as possible substitutes for hightemperature molten salts. In this thesis, uranyl was dissloved in differentionic liquid. The electrochemical behavior and dissolution behavior ofuranyl were discussed, then we use the potentio-static method forelectrodeposition in order to recycle the uranium. The resultsdemonstrate that the ionic liquid is feasible and applicable to be used inthe reprocessing spent nuclear fuels.In the first chapter, the main signification of the thesis, as well as thedefinition, classification, properties and applications of ILs wereintroduced. The recent researches on the topic of applying ILs in manyfields, including utility of ILs in metal electrodeposition, the solution behavior and elctrochemical behavior of lanthnide and actinide in ionicliquid were summarized. At last, the research contents, aim and afeasible technology roadmap of the thesis were presented.The electrochemical behaviors of the U (VI) in C4MimCl mixture withwater were investigated in the second chapter. The electrochemicalreduction of U(VI) was proved to involve a process ofU(VI)→U(V)→UO2. The potentiostatic electrolysis at-0.85V wascarried out and XRD results confirm the formation of the UO2. As thecontent of water in ionic liquid increased, the reversibility between U(VI)to U(V) would been disturbed and the reduction potent of U(V) graduallyremoved positively. It is also found that the diffusion coefficients of U(VI)in the C4MimCl will be improved from4.74×10-8cm2/s to2.12×10-7cm2/s with the increasing of the water content from0.1wt%to4wt.%.This work clearly suggests that the electrochemical properties of U(VI) inC4MimCl would be obviously effected by the little amount of water, andthe addition of appropriate amount of water greatly improve theelectrodeposition of uranium oxide from C4MimCl solvent.The third chapter investigated electrochemical behaviors of U(VI) inbutyltrimethylammonium bis(trifluoromethane sulfonimide)(N1113NTf2)hydrophobic ionic liquid and different concentrations of uranyl nitratewere studied by chronopotentiometry (CP) and cyclic voltammetry (CV)and square wave voltammetry(SWV). The electrochemical reduction of U(VI) was identified to been reduced to U(III) at the electrochemicalwindown of ionic liquid N1113NTf2, and the detailed process can beproved as follow:. The product ofpotentiostatic electrolysis deposition on the surface of stainless steelelectrode was confirmed with the formation of the UO2. Also therelationship between the electrodeposition potention and the surfacemicrotopography was discussed.Finally, the main conclusions and innovations of the thesis weresummarized, and further researches were prospected.