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  • 1 Institute for Physics and Nuclear Engineering P.O. Box MG-6 R-76900 Bucharest-Magurele (Romania)
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The intermolecular ligand exchange in uranyl nitrate complexes with TBP and TOPO is studied by31P-NMR. The constant rates at 25°C in CCl4 are: (8.47±1.86)·103 s–1 for U-TBP and (1.3±0.04)·104M–1·s–1 for U-TOPO system. The very similar activation parameters values of the ligand exchange suggest the same mechanism for both systems, namely an one-step interchange mechanism. The differences between the systems regarding the rate equations and the extraction properties are discussed.