Solvent Modification in Ion-Pair Extraction: Effect on Sodium Nitrate Transport in Nitrobenzene Using a Crown Ether |
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Authors: | Email author" target="_blank">Tatiana?G?LevitskaiaEmail author Gregg?J?Lumetta |
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Institution: | (1) Pacific Northwest National Laboratory, MSIN P7-22, Richland, Washington, P.O. Box 999, 99352 |
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Abstract: | A comparative quantitative analysis of the effect of solventmodifiers on the ion-pair extraction of an inorganic salt by a
crown ether was conducted with the aim of advancing the understanding of transport of highly hydrophilic metal ions from aqueous
salt solutions. Two classes of solvent modifiers that possess electron-pair donor (EPD) or hydrogen-bond donor (HBD) groups
were investigated. The equilibrium constants corresponding to the extraction of sodium nitrate into nitrobenzene (NB) employing
model neutral host cis-syn-cis-dicyclohexano-18-crown-6 (compound 1) with and without solvent modifier were determined using the SXLSQI computer model. For a series of EPD modifiers—including
tri-n-butyl- and tri-phenylphosphate, tri-n-butyl- and tri-phenylphosphine oxide, N,N-di-n-butyl- and N,N-di-phenylacetamide—the enhancement of the NaNO3 extraction by compound 1 was found to be dependent on the hydrogen-bond acceptance ability of the modifier as quantified by the β solvatochromic parameter.
A HBD modifier 3,5-di-t-butylphenol (compound 8), which forms strong hydrogen bonds with nitrate anion in NB, exhibited even greater enhancement of the NaNO3 extraction by compound 1. The determined extraction constants were correlated with the β- or α-solvatochromic parameters of the solvent modifiers
and linear trends were observed. Hydrogen bond interaction between compound 8 and nitrate anion in the presence of the sodium-loaded crown ether in the extraction phaseswas studied by vibrational spectroscopy. |
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Keywords: | Solvent modifiers solvent extraction ion transport sodium nitrate crown ether |
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