PEO−[M(CN)5NO]x- (M = Fe, Mn, or Cr) Interaction as a Driving Force in the Partitioning of the Pentacyanonitrosylmetallate Anion in ATPS: Strong Effect of the Centra

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• 作者：Luis Henrique M. da Silva ; Maria C. Hespanhol da Silva ; Kelly R. Francisco ; Marcus V. C. Cardoso ; Luis A. Minim ; Jane S. R. Coimbra
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：September 18, 2008
• 年：2008
• 卷：112
• 期：37
• 页码：11669-11678
• 全文大小：238K
• 年卷期：v.112,no.37(September 18, 2008)
• ISSN：1520-5207

文摘

The partitioning behavior of pentacyanonitrosilmetallate complexes[Fe(CN)₅NO]²⁻, [Mn(CN)₅NO]³⁻, and [Cr(CN)₅NO]³⁻has been studied in aqueous two-phase systems (ATPS) formed by adding poly(ethylene oxide) (PEO; 4000 g mol⁻¹) to an aqueous salt solution (Li₂SO₄, Na₂SO₄, CuSO₄, or ZnSO₄). The complexes partition coefficients (K_complex) in each of these ATPS have been determined as a function of increasing tie-line length (TLL) and temperature. Unlike the partition behavior of most ions, [Fe(CN)₅NO]²⁻ and [Mn(CN)₅NO]³⁻ anions are concentrated in the polymer-rich phase with K values depending on the nature of the central atom as follows: ≫ > The effect of ATPS salts in the complex partitioning behavior has also been verified following the order Li₂SO₄ > Na₂SO₄ > ZnSO₄. Thermodynamic analysis revealed that the presence of anions in the polymer-rich phase is caused by an EO−[M(CN)₅NO]^x− (M = Fe, Mn, or Cr) enthalpic interaction. However, when this enthalpic interaction is weak, as in the case of the [Cr(CN)₅NO]³⁻ anion ( < 1), entropic driving forces dominate the transfer process, then causing the anions to concentrate in the salt-rich phase.