Document Type : Research Paper
Authors
1 Nuclear Science and Technology Research Institute, Nuclear Fuel Cycle Research School, Chemical conversion and fuel manufacturing group
2 Nuclear Science and Technology Research Institute Nuclear Fuel Cycle Research School
3 NSTRI
Abstract
Liquid-liquid extraction is one of the most common methods for purifying thorium from multicomponent aqueous solutions. In this study, the ability of different organic solvents, including tributyl phosphate (TBP), di-2-ethylhexyl phosphoric acid (DEHPA), and di(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), to separate thorium from a multicomponent aqueous nitrate solution containing uranium, vanadium, and iron elements was investigated. The experimental results showed that the extraction efficiency of elements for tributyl phosphate and di-2-ethylhexyl phosphoric acid is uranium > thorium > iron > vanadium and for Cyanex 272 is thorium > uranium > vanadium > iron, respectively. Also, the separation factor of thorium compared to uranium, vanadium, and iron by Cyanex 272 was obtained as 63.4, 384.4 and 615.6, respectively. The investigation of various process parameters on the solvent extraction process showed that in the contact time of 15 minutes, the pH of the aqueous phase equal to 0.5, the ratio of aqueous to organic phase equal to 1 and the concentration of Cyanex 272 equal to 0.1 M, the highest percentage of thorium extraction is obtained and the extraction efficiency of thorium, uranium, vanadium and iron is equal to 98.6, 37.8, 10.6 and 11.1 percent, respectively. Also, different mineral acids including nitric acid, sulfuric acid and hydrochloric acid solutions were studied for the stripping process from the loaded organic phase. The results of the stripping process showed that by using 4 M sulfuric acid solution, the thorium stripping efficiency above 91% from the loaded organic phase can be reached.
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