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SUMMARYThe main objective of the work in the present thesis is to study the extraction of cerium (IV) from nitric acid medium by TBP in kerosene under Purex process conditions. Investigation on the redox / stripping of Ce(IV) from TBP / kerosene solution using dThe thesis is classified into three chapters, namely, introduction, experimental, and results and discussion.The first chapter is the introduction which includes some aspects on the chemistry of uranium and cerium, solvent extraction, and Purex process and reprocessing. It also contains a literature survey which is related to the present work.The second chapter, “experimental,” contains detailed information concerning the chemicals and reagents. Instrumentation as well as different experimental techniques and procedures used are also included.The third chapter, “results and discussion,” is classified into three parts, namely, stabilization of cerium (IV), extraction of Ce(IV), and reductive stripping of Ce(IV).The first part is concerned with the stabilizing investigation of cerium (IV) in nitric acid medium prior to the extraction investigations. In this respect, different stabilizing agents such as sulphamic acid and sodium bromate were used. In case of usingIn the case of stabilizing cerium (IV) by sodium bromate, the stability was found to increase with the increase in nitric acid concentration. Generally, from these results it was found that Ce(IV) is more stable in case of using sulphamic acid than in casThe second part of this chapter is concerned with the batch extraction investigations of Ce(IV) using TBP in kerosene. In this part, based on the first part of this chapter, the extraction of cerium (IV) from 3 M nitric acid containing 0.2 M sulphamic aciFurthermore, the obtained results show that a part of Ce(IV) is reduced to Ce(III) during the extraction process. When the reduced part of Ce(IV) was measured as Ce(III) during the investigated parameters of the extraction process it was found that, Ce(IIFrom the extraction investigations it was found that the best extraction conditions for Ce(IV) are when using 10 % TBP in kerosene, 5 M HNO3, and 0.2 M sulphamic acid (under pre – equilibration conditions).When the extraction process was performed but with using 0.2 M sodium bromate instead of sulphamic acid it was found that a part of Ce(IV) was not reduced to Ce(III), compared with the case of using sulphamic acid. The extraction increased with the increaFor cerium – uranium separation, the extraction investigation of U(VI) under these optimum extraction conditions of Ce(IV) were studied. The obtained results show that fast extraction reaction of U(VI) was observed where two minutes are sufficient for reaIn the reductive stripping investigations of cerium (IV) from the organic to aqueous phase, three stripping agents in nitric acid medium were used, namely, U(IV), EDTA, and 30 % (1.1M) H2O2. These investigation for cerium – uranium separation by reductionIn case of using U(IV) in nitric acid medium as a reductive stripping agent, the results obtained indicate that the stripping of Ce(IV) increases with the increase in U(IV) concentration till 8.4 x 10-3 M then remains constant with further increase in [U(When EDTA was used as a reductive strippant, the stripping of Ce(IV) decreased with the increase in EDTA and nitric acid concentrations. The preferred nitric acid concentration used is 3M with shaking time of 10 minutes. The stripping of Ce(IV) from the lIn case of using hydrogen peroxide (30% H2O2) as a reductive strippant, the results show that the stripping of Ce(IV) decreases with the increase in hydrogen peroxide concentration and with the increase in nitric acid concentration. The nitric acid concen• General ConclusionThe use of EDTA or H2O2 is better than the use of U(IV) in the reductive stripping process of Ce(IV) this is due to the following:? Lower [EDTA] and [H2O2] are used rather than [U(IV)];where 0.001M of EDTA and 2 X 10-3 M of H2O2 are enough to givevery efficient stripping of Ce(IV) (about 50 % and 60 % for H2O2 andEDTA respectively), while higher value of 0.0126 M U(IV) is usedfor effective stripping (about 30 %).? The shaking time required for maximum reductive stripping in case of EDTA and H2O2 is shorter than in case of using U(IV);where efficient stripping of Ce(IV) is reached after 10 minutes in caseof using EDTA and H2O2 while in case using U(IV) the required timeis 90 minutes.? Higher stripping percent is obtained in case of using EDTA and H2O2 than in case of using U(IV);where the higher stripping percent approaches about 50 % and 60 %in case of using H2O2 and EDTA repectively, while it reaches amaximum of 30 % in case of using U(IV).? EDTA or H2O2 are economic reagents compared with the use of U(IV).* However, the use of U(IV) could be preferred only because it is oxidized to U(VI) and so does not add to the aqueous waste volumes.till reach its maximum at organic : aqueous phase ratio 1 : 3 after that remain constant
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