Guilherme Rodrigues

Phase diagrams of aqueous two-phase systems composed of PEO1500 + salt (di-potassium phosphate + potassium hydroxide or ammonium sulfate or zinc sulfate) + water were determined at (283.15, 298.15, and 313.15) K. All systems produce a large two-phase region; however the influence of temperature on the binodal position seems to be very small. By analyzing the effects of ammonium sulfate or zinc sulfate, it was observed that zinc was more effective in promoting phase separation than ammonium. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation. In this paper, aqueous two-phase systems data for nine ternary systems are correlated by using the NRTL model and UNIFAC for the activity coefficient. The results are very satisfactory, with root mean square deviations between experimental and calculated compositions as low as 0.99 and 1.21%, respectively. However the NRTL model better represents the systems in study, when compared with UNIFAC.► Liquid–liquid equilibrium data of new aqueous two phase systems (ATPS) were obtained. ► The cation and anion effects on thermodynamic properties of biphasic systems were analyzed. ► Intermolecular interactions parameters were obtained by thermodynamic modeling.

The extraction behavior of the ions Ni(II), Fe(III), Cd(II), Co(II), Zn(II) and Cu(II) was studied as a function of the amount of extractant added, in aqueous two-phase systems (ATPS) formed mostly by water and without the use of any organic solvent. The others ATPS components were a triblock copolymer (L35) and Na2SO4. Two types of water-soluble extractants (thiocyanate, iodide) and one slightly water-soluble extractant [1-nitroso-2-naphthol (1N2N)] were studied separately. It must be emphasized that this is the first study using a slightly water-soluble complexant for the metallic partition in ATPS, which was not a restrictive factor to the technique as believed. The extraction to the L35 rich-phase of all suited metal ions was insignificant without extractant addition. However, the effectiveness of SCN− in extracting metal ions in the system could be observed in the following sequence: Zn(II) ≅ Co(II) > Cd(II) > Cu(II) > Fe(III) > Ni(II), with Zn(II), Co(II) and Cd(II) quantitatively extracted and Cu(II) enriched by almost 80%. In the case of the I− extractant, all metal ions, except Cd(II) and Cu(II), remained in the salt-rich phase, providing favorable conditions to the selective separation of Ni(II), Co(II) and Fe(III) ions from Cd(II). The results show that, at pH 7.2, L35/Na2SO4/H2O ATPS can be used with 1N2N as extractant, to separate Co(II) from a complex mixture containing Fe(III), Zn(II) and Cd(II). It was observed, when using 1N2N, that a significant increase in metal extraction takes place as the pH increases, except for Cd(II) and Zn(II).

An environmentally safe procedure has been developed for the extraction, separation and determination of metal ions using a monosegmented flow analysis technique that exploits an aqueous two-phase system (ATPS-MSFA). The ATPS-MSFA method was applied for the determination of cobalt, based on the reaction between Co(II) and KSCN, which produces a metallic complex that spontaneously partitions to the top phase of the ATPS composed of poly(ethylene oxide), ammonium sulfate and water. The linear range was 5.00 to 500 μmol kg(-1) (R = 0.9998; n = 13) with a coefficient of variation equal to 1.14% (n = 7). The method yielded a limit of detection and a limit of quantification of 2.17 and 7.24 μmol kg(-1), respectively. The ATPS-MSFA method was applied to the determination of cobalt in a nickel-cadmium battery sample and the results were validity with flame atomic absorption spectrometry using addition standard.

Phase diagrams of aqueous two-phase systems composed of poly(ethylene) glycol (PEG) 1500, lithium sulfate, or magnesium sulfate were determined at (283.15, 298.15, and 313.15) K and of PEG 1500 + sodium sulfate were obtained at (278.15, 298.15, 305.65, and ...

Phase diagrams of aqueous two-phase systems (ATPS) composed of F68 triblock copolymer + salt + water were constructed at different temperatures. The ATPS composed of F68 + (NH 4 ) 3 C 6 H 5 O 7 + H 2 O was investigated at (278.15, 288.15, and 298.15) K, and the F68 ...