Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers
- Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.
Crown ethers dissolved in suitably modified aliphatic kerosene diluents can be employed to extract technetium as pertechnetate anion (TcO{sub 4}{sup {minus}}) with good extraction ratios from realistic simulants of radioactive alkaline nitrate waste. The modifiers utilized are non-halogenated and non-volatile, and the technetium can be removed from the solvent by stripping using water. The crown ethers bis-4,4{prime}(5{prime})[(tert-butyl)cyclohexano]-18-crown-6 (di-t-BuCH18C6) and dicyclohexano-18-crown-6 (DCH18C6) provide stronger TcO{sub 4}{sup {minus}} extraction than dicyclohexano-21-crown-7 and 4-tert-butylcyclohexano 15-crown-5. Whereas DCH18C6 provides somewhat higher TcO{sub 4}{sup {minus}} extraction ratios than the more lipophilic di-t-BuCH18C6 derivative, the latter was selected for further study owing to its lower distribution to the aqueous phase. Particularly good extraction and stripping results were obtained with di-t-BuCH 18C6 at 0.02 M in a 2:1 vol/vol blend of tributyl phosphate and Isopar{reg_sign} M. Using this solvent, 98.9% of the technetium contained (at 6 {times} 10{sup {minus}5} M) in a Double-Shell Slurry Feed (DSSF) Hanford tank waste simulant was removed following two cross-current extraction contacts. Two cross-current stripping contacts with deionized water afforded removal of 99.1% of the technetium from the organic solvent.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 86950
- Report Number(s):
- CONF-9505101--6; ON: DE95014200
- Country of Publication:
- United States
- Language:
- English
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