skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers

Abstract

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.

Authors:
; ; ;  [1]
+ Show Author Affiliations
  1. Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.
Publication Date:
Research Org.:
Oak Ridge National Lab., TN (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
86950
Report Number(s):
CONF-9505101-6
ON: DE95014200; TRN: 95:017291
DOE Contract Number:
AC05-84OR21400
Resource Type:
Technical Report
Resource Relation:
Conference: Conference on challenges and innovations in the management of hazardous waste, Washington, DC (United States), 10-12 May 1995; Other Information: PBD: [1995]
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; TECHNETIUM; SOLVENT EXTRACTION; CROWN ETHERS; SOLVENT PROPERTIES; RADIOACTIVE WASTE PROCESSING; NITRATES; TECHNETIUM OXIDES; VOLATILITY; VITRIFICATION; EXPERIMENTAL DATA; SODIUM COMPOUNDS; POTASSIUM COMPOUNDS; WASTE RETRIEVAL; TANKS

Citation Formats

Bonnesen, P.V., Presley, D.J., Haverlock, T.J., and Moyer, B.A.. Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers. United States: N. p., 1995. Web. doi:10.2172/86950.
Copy to clipboard
Bonnesen, P.V., Presley, D.J., Haverlock, T.J., & Moyer, B.A.. Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers. United States. doi:10.2172/86950.
Copy to clipboard
Bonnesen, P.V., Presley, D.J., Haverlock, T.J., and Moyer, B.A.. Sat . "Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers". United States. doi:10.2172/86950. https://www.osti.gov/servlets/purl/86950.
Copy to clipboard
@article{osti_86950,
title = {Removal of technetium from alkaline nuclear-waste media by a solvent-extraction process using crown ethers},
author = {Bonnesen, P.V. and Presley, D.J. and Haverlock, T.J. and Moyer, B.A.},
abstractNote = {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.},
doi = {10.2172/86950},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 1995},
month = {Sat Jul 01 00:00:00 EDT 1995}
}
Copy to clipboard
Technical Report:
View Technical Report (0.98 MB)
DOI:  10.2172/86950
Save / Share:
Export Metadata
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.

  • ; ; ; ...
    The chemical development of a new crown-ether-based solvent-extraction process for the separation of (Tc) from alkaline tank-waste supernate is ready for counter-current testing. The process addresses a priority need in the proposed cleanup of Hanford and other tank wastes. This need has arisen from concerns due to the volatility of Tc during vitrification, as well as {sup 99}Tc`s long half-life and environmental mobility. The new process offers several key advantages that direct treatability--no adjustment of the waste composition is needed; economical stripping with water; high efficiency--few stages needed; non-RCRA chemicals--no generation of hazardous or mixed wastes; co-extraction of {sup 90}Sr;more » and optional concentration on a resin. A key concept advanced in this work entails the use of tandem techniques: solvent extraction offers high selectivity, while a subsequent column sorption process on the aqueous stripping solution serves to greatly concentrate the Tc. Optionally, the stripping solution can be evaporated to a small volume. Batch tests of the solvent-extraction and stripping components of the process have been conducted on actual melton Valley Storage Tank (MVST) waste as well as simulants of MVST and Hanford waste. The tandem process was demonstrated on MVST waste simulants using the three solvents that were selected the final candidates for the process. The solvents are 0.04 M bis-4,4{prime}(5{prime})[(tert-butyl)cyclohexano]-18-crown-6 (abbreviated di-t-BuCH18C6) in a 1:1 vol/vol blend of tributyl phosphate and Isopar{reg_sign} M (an isoparaffinic kerosene); 0.02 M di-t-BuCH18C6 in 2:1 vol/vol TBP/Isopar M and pure TBP. The process is now ready for counter-current testing on actual Hanford tank supernates.« less

  • ; ;
    The crown ether bis-4,4`(5`)[(tert-butyl)cyclohexano]-18-crown-6 can be utilized in a solvent-extraction process for the removal of technetium as pertechnetate ion, TcO{sub 4}{sup {minus}} from solutions simulating highly radioactive alkaline defense wastes (``tank wastes``) stored at several sites in the United States. The process employs non-halogenated and non-volatile diluents and modifiers and includes an efficient stripping procedure using only water. More than 95% of the pertechnetate present at 6 {times} 10{sup {minus}5} M in Melton Valley (Oak Ridge, TN) and Hanford (Washington) tank-waste simulants was removed following two cross-current extraction contacts using 0.02 M bis-4,4`(5`)[(tertbutyl)cyclohexano]- 18-crown-6 in 2:1 vol/vol TBP/Isopar{reg_sign} M diluentmore » at 25 C. Similarly, for both simulants, more than 98% of the pertechnetate contained in the solvent was back-extracted following two cross-current stripping contacts using deionized water.« less

  • ; ; ; ...
    An alkaline-side solvent extraction process for cesium removal from Savannah River Site (SRS) tank waste was evaluated experimentally using a laboratory-scale centrifugal contactor. Single-stage and multistage tests were conducted with this contactor to determine hydraulic performance, stage efficiency, and general operability of the process flowsheet. The results and conclusions of these tests are reported along with those from various supporting tests. Also discussed is the ability to scale-up from laboratory- to plant-scale operation when centrifugal contractors are used to carry out the solvent extraction process. While some problems were encountered, a promising solution for each problem has been identified. Overall,more » this alkaline-side cesium extraction process appears to be an excellent candidate for removing cesium from SRS tank waste.« less

  • ; ;
    This fundamental research on combined cesium, strontium, and actinide separation from alkaline media by solvent extraction addresses the EM need for more efficient processes for the combined separation of these elements.

  • ; ;
    This fundamental research on combined cesium, strontium, and actinide separation from alkaline media by solvent extraction addresses the EM need for more efficient processes for the combined separation of these elements.