Chemistry of actinide elements: some aspects of the solvent extraction of uranium(IV) and uranium(VI)
Thesis. Studies on some aspects of solvent extraction of uranium(IV) and uranium(VI) are reported. The investigation is described in two parts. The first part deals with the determination of stability constants of nitrate and sulfate complexes of uranium(IV) by solvent extraction. Uranium(IV) was extracted from nitric and sulfuric acid solutions by 20% benzene solution of tributyl phosphate (TBP) and 0.1M thenoyltrifluoracetone (HTTA) in benzene at an ionic strength of 3.8 and an acidity of 1M. Uranium(IV) concentration in both the phases was estimated by a colorimetric method. Stability constants of both nitrate and sulfate complexes were calculated by various methods. For nitrate complexes, values of BETA obtained by TBP extraction were found to be very high compared to the values obtained by HTTA extraction data. For sulfate complexes, the values of BETA obtained by TBP extraction were in good agreement with reported values and values obtained by HTTA extraction were comparatively lower. The computed value of BETA = 1.2 for nitrate complex and BETA /sub 1/ = 188 and BETA /sub 2/ = 7358 for sulfate complexes by HTTA extraction seem to be more reliable than by TBP extraction because of the simplicity of the underlying assumption in the HTTA system. The second part of the study deals with the study of the effect of temperature and salt concentration on the synergetic extraction of uranyl ion with HTTA and neutral donors. Distribution ratios for the synergetic species UO/sub 2/(TTA)/sub 2/S where S = TOPO, TBP, DBSO, and DPSO were determined at various temperatures from 30 deg to 70 deg at a pH = 1.6 in HCl medium. The equilibrium constant (K) for the formation of the species was evaluated from the distribution data at various temperatures. From a plot of log K vs. 1/T, DELTA H values were calculated for all the systems. The results indicated that whereas TBP and sulfoxide complexes are enthalpy stabilized, both enthalpy and entropy contribute to the stability of UO/sub 2/(TTA)/sub 2/ TOPO. The effect of salt concentration in the aqueous phase on the extraction of the species UO/sub 2/(TTA)/sub 2/S was studied by distribution measurement in the above system, in the presence of varying concentrations of the perchlorates of lithium, sodium, and ammonium. The distribution ratio was found to increase with salt concentration in the aqueous phase. The enhanced extraction in the presence of lithium perchlorate was correlated with its larger hydrated ionic radius. (INIS)
- Research Organization:
- Bombay Univ. (India)
- NSA Number:
- NSA-29-002466
- OSTI ID:
- 4425321
- Report Number(s):
- INIS-mf-360
- Resource Relation:
- Other Information: Thesis. Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- India
- Language:
- English
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