Kinetics of the complexation of UO2(NO3)(2) with tributyl phosphate (TBP) in xylene

Citation
Ak. Mohammed et al., Kinetics of the complexation of UO2(NO3)(2) with tributyl phosphate (TBP) in xylene, SOLVENT EXT, 18(5), 2000, pp. 809-820
Citations number
24
Categorie Soggetti
Chemistry
Journal title
SOLVENT EXTRACTION AND ION EXCHANGE
ISSN journal
07366299 → ACNP
Volume
18
Issue
5
Year of publication
2000
Pages
809 - 820
Database
ISI
SICI code
0736-6299(2000)18:5<809:KOTCOU>2.0.ZU;2-V
Abstract
The kinetics of ligand exchange between bulk solution TBP and uranyl nitrat e bound TBP in o-xylene has been investigated by P-31 dynamic NMR spectrosc opy. First order ligand exchange rate constant, k, and the activation energ y for the uranyl nitrate-TBP system were determined from plots of transvers e relaxation rates (In (1/tau)) versus reciprocal temperature (1/T). Using the Eyring equation, the average values of activation enthalpy, Delta H* (3 0.8+/-5.1 kJ.mole(-1)), and activation entropy, Delta S* (-109+/-19 J/mol.K ) have been calculated. The negative entropy of activation value indicates an increase in order on proceeding from the reactants to the activated comp lex. Therefore, an associative mechanism may be proposed for the ligand exc hange reaction between UO2(NO3)(2) TBP2 and TBP. Equilibration of the extra ctant phase with 1.0 M HCl did not change the ligand exchange rate constant s or the activation parameters appreciably. These results are discussed in comparison with previous reports on TBP exchange rates for this system.