Estudo das forças motrizes que regem a partição dos complexos [Fe(CN)5NO]2- e [Cr(CN)5NO]3- em SABs formados por poli(óxido de etileno) e sulfatos / Study of drivig forces partitioning behavior [Fe(CN)5NO]2- and [Cr(CN)5NO]3- complexes in Poli(ethylene oxide) and sulphates ATPS

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

In this dissertation a critical analysis in the area of partitioning ions in aqueous two phase systems (ATPS) was done, exposing some models that explain the distribution of those molecules in the phases. In a second study, data of phase diagram formed by poly (ethylene oxide) of molar mass 4000 g mol-1 (PEO 4000) and sulphate zinc at 298 K was obtained. It was also determined the partitioning coefficient K, that is defined as being the ratio of concentration of the complex in the top and bottom phases, and the thermodynamic parameters of transfer (ΔtrG, ΔtrH and ΔtrS) of the complex anions [Fe(CN)5NO]2-,[Cr(CN)5NO]3- in PEO 4000 and sulphate salts (Na2SO4, Li2SO4, ZnSO4) ATPS, in four temperatures (278, 298, 308 and 318)K. Partitioning coefficients for both complexes are strongly dependent of ATPS electrolyte nature. Iron complex transfer from bottom to top phase follows the order Li2SO4 >>Na2SO4>ZnSO4, while the chromium complex follows the order ZnSO4 >>Li2SO4>Na2SO4. In lithium and sodium sulphates ATPS, KFe/KCr >>1, while in zinc sulphate ATPS, two complexes have obtained similar values of K. Values of thermodynamic parameters were also determined for the complex [Fe(CN)6]3- in ATPS composed by sodium and lithium sulphates. The transfer of complexes [Fe(CN)5NO]2- and [Fe(CN)6]3 - is spontaneous and driven by enthalpic forces, and for [Fe(CN)5NO]2- high value of partitioning coefficient was attributed to the specific interactions that happen between the anion and polymer, suggested by the variation of stretching frequency of bond Fe-NO in polymeric solutions. However, no variation in stretching frequency of bond Cr-NO was verified, suggesting a weak interaction between the polymer and the complex anion [Cr(CN)5NO]3-, indicating that the distribution of this anion in ATPS is governed by forces of entropic nature.

ASSUNTO(S)

efeito da temperatura macromolecules aqueous two phase systems temperature effects compostos complexos complex compounds macromoléculas força motriz fisico-quimica sistemas aquosos bifásicos driving forces

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