The effects of halide anions on the partitioning behavior of pertechnetate in polyethylene glycol-based aqueous biphasic systems

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Separation Science and Technology

DOI:https://doi.org/10.1080/01496399708003224· OSTI ID:471770

Rogers, R D; Zhang, Jianhua; Griffin, S T ^[1]

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1. Northern Illinois Univ., DeKalb, IL (United States)

The pertechnetate anion quantitatively partitions to the upper polyethylene glycol (PEG)-rich phase in aqueous biphasic systems (ABS) formed by the addition of aqueous high-molecular-weight PEG solutions to aqueous water-structuring salt solutions. Most metal cations partition to the salt-rich phase in these systems. Other matrix ions, such as those that might be present in real-world waste streams, affect the distribution ratios observed for TcO{sub 4}{sup -}, however, the effects are not well understood. The halide ions F{sup -}, Cl{sup -}, Br{sup -}, I{sup -} represent a wide range of water-structuring to chaotropic ions. The heavier halide ions have distribution ratios above one and are observed to follow the order D{sub I} > D{sub Br} > D{sub Cl}. These ions depress D{sub Tc}. Fluoride salts-out PEG and thus partitions primarily to the salt-rich phase and fluoride increases D{sub Tc}. These trends can be correlated with the ions{close_quote} Gibbs free energies of hydration ({Delta} G{sub hyd}), a measure of their interactions with water. Based upon these results, it is possible to predict which ions will depress, elevate, or not affect D{sub Tc} for a given PEG-ABS based upon the matrix ion`s {Delta} G{sub hyd}.

• Sponsoring Organization: USDOE
• OSTI ID: 471770
• Report Number(s): CONF-951057--
• Journal Information: Separation Science and Technology, Journal Name: Separation Science and Technology Journal Issue: 1-4 Vol. 32; ISSN 0149-6395; ISSN SSTEDS
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
AQUEOUS SOLUTIONS
HALIDES
PERTECHNETATES
POLYETHYLENE GLYCOLS
SOLVENT EXTRACTION