Study On The Extraction Properties Of Uranium (Ⅵ ),thorium (Ⅳ ) In Solution Using Db18c6- Ethyl Acetate System

In the first chapter, the coordination characteristics of crown ether was introduced in brief, including good coordination ability, unique coordination selectivity and the factors which may affect the stablity and selectivity of crown ethe(effects of ligands, ions and solvent). The progress about the application of crown ether on separating metal ion was also outlined, the research progress of uranium (Ⅵ) extraction reviewed as well. Furthermore, the significance and contents of this topic were inducted and summarized.In the second chapter , in the condition of DB18C6 as extractant, the impact of a variety of diluents was investigated, such as salting agent and organic medium on the extraction of uranium (Ⅵ). Ethyl acetate as determined agent, 0.1mol /L of KH2PO4 as salting agenthe, salicylic acid medium for solvent extraction system was determined. In the selected conditions of the extraction system, the extraction rate of 1×10-4mol/L of uranium (Ⅵ) was 82.5%, and the apparent extraction equilibrium constant and thermodynamic functions were calculated.In the third chapter, after the extraction of uranium(Ⅵ) in the extraction system of DB18C6 as extractant, acid medium as media , ethyl acetate as diluent, the anti-extraction of the uranium (Ⅵ) from organic phase was investigated. By screening strip feed, the acidity, concentration, temperature, various aspects which affecting strip were discussed, and the optimum strip feed which afforded better stripping rate was obtained.In the forth chapter, th extraction process of using DB18C6-ethyl acetate system for uranium (Ⅵ) in solution was coordination reactionit of DB18C6 and uranium (Ⅵ). After the separation of water phase and oil phase , the oil phase was eluted, dried, recrysted, analyzed by elemental analysis, exosyndromed using infrared spectrum, thermogravimetric Analysis and other methods. Then, the composition of [UO2 (DB18C6)] [NO3] [C7H5O3]｝·2H2O was presumedIn the fifth chapter, there was natural similarity between uranium (Ⅵ) and thorium (Ⅳ) . The extraction system of DB18C6 as extractant, ethyl acetate as diluent, KH2PO4 as salting agent and salicylic acid for the acidic medium was used for extraction of thorium (Ⅳ) in solution. In the selected experimental conditions, the simulation samples was determined with this system, the extraction rate is up to 88.5% in 1×10-4 mol/L thorium (Ⅳ) solution, the apparent equilibrium constant and thermodynamic functionst were also calculated.