Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO

摘要

DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660 (+-) 0.092 at 25 C, and extraction enthalpy is -5. 46 (+-) 0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1,213,000 (+-) 35,600 at 25 C; reaction enthalpy was -9.610 (+-) 0.594 kcal/mol. Nitration complexation constant is 8.412 (+-) 0.579, with an enthalpy of -10.72 (+-) 1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of perhaps 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.