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Abstract: We have investigated the extraction behavior of the metallic ions Co(II), Fe(III) and Ni(II) as a function of the amount of potassium thiocyanate used as an extracting agent, using the following aqueous two-phase systems (ATPS): PEO+(NH4)2SO4 +H2O, PEO+Li2SO4 +H2O, L35+(NH4)2SO4 +H2O and L35+(Li)2SO4 +H2O. Metal extraction from the salt-rich phase to the polymer-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and polymer that forms the ATPS. Maximal extraction percentages were obtained for Co(II) (99.8%), Fe(III) (12.7%) and Ni(II) (3.17%) when the ATPS was composed of PEO1500+(NH4)2SO4 +H2O containing 1.4mmol of KSCN at pH 4.0, providing separation factors as high as S Co,Fe =3440 and S Co,Ni =15,300. However, when the same ATPS was used at pH 2.0, the maximal extraction percentages for iron and nickel were 99.5% and 4.34%, respectively, with S Fe,Ni equal to 4380. The proposed technique was shown to be efficient in the extraction of Co(II) and Fe(III), with large viability for the selective separation of Co(II) and Fe(III) ions in the presence of Ni(II). [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine the thermodynamic parameters (Δ tr G, Δ tr H and Δ tr S) associated with lysozyme and conalbumin partitioning in aqueous two-phases systems (ATPS). Influence of salt type and polyethylene glycol (PEG) concentrations on the partition coefficient of lysozyme and conalbumin from egg white was studied. The evaluated ATPS were composed of PEG 1500 and inorganic salts (sodium citrate and sodium sulfate) at a temperature of 25°C and pH 7.0, with PEG 1500gmol−1 concentrations of 14%, 16% and 18% (mass basis). Partitioning of lysozyme in PEG–citrate ATPS was enthalpically driven, however the PEG–sulfate ATPS was entropically driven. The tested systems can be employed for the separation of these two proteins in egg white, due to the fact that lysozyme migrates toward the polymeric phase and conalbumin to the saline phase in both ATPS. A high recovery of conalbumin in the saline phase of the PEG–sulfate ATPS was determined to be enthalpically driven. [Copyright &y& Elsevier]

Abstract: Partitioning of the natural dye norbixin has been studied in aqueous two-phase system (ATPS) that are formed by mixing aqueous solutions of a polymer (or copolymer) and an organic salt (sodium tartrate or succinate). In this work, the norbixin partition coefficient (K N) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that K N is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced K N values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (Δtr G, Δtr H, Δtr S) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions. [Copyright &y& Elsevier]

Abstract: The phase diagrams of PEO1500+sodium tartrate+water, PPO400+sodium tartrate+water, PEO1500+sodium succinate+water, PPO400+sodium succinate+water, PEO1500+sodium citrate+water, PPO400+sodium citrate+water and PPO400+sodium acetate+water aqueous two-phase systems were determined at (283.15, 298.15, and 313.15)K. Both equilibrium phases composition were analyzed by conductimetry and refractive index. In this paper, the influences of polymer hydrophobicity, salt nature and temperature on the phase diagram were analyzed. The phase separation processes was endothermic and the hydrophobic increase make easier the phase splitting, while the electrolyte capacity to induce phase separation follow the order: citrate>tartrate>succinate. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation. The experimental data were correlated with the NRTL model for the activity coefficient, with estimation of new interaction energy parameters. The results, analyzed in terms of root mean square deviations between experimental and calculated compositions, were considered satisfactory. [Copyright &y& Elsevier]

Abstract: Partition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na2SO4 and Li2SO4). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li2SO4 ≫Na2SO4. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li2SO4 and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li2SO4 and low pH values within the ranges studied. [Copyright &y& Elsevier]

Abstract: This work aimed to study the partition of cheese whey proteins α-lactoalbumin and β-lactoglobulin using aqueous two-phase system by applying the cloud point extraction technique. The cloud point temperatures were determined under different concentrations of copolymer and salt. The system providing the best protein separation conditions was 20mass% of copolymer PE61 and potassium phosphate salt solution of 100mM, at pH 7. The protein α-lactoalbumin remained preferentially in the aqueous phase and the β-lactoglobulin was transferred to the copolymer phase. [Copyright &y& Elsevier]

Abstract: This study evaluates the influence of type of salt and temperature on the partition coefficient of caseinomacropetide (CMP) to determine the best conditions for the recovery of CMP in aqueous two-phase systems (ATPS) composed by poly(ethylene glycol) (PEG) 1500 and an inorganic salt (potassium phosphate, sodium citrate, lithium sulfate or sodium sulfate). In all systems, CMP presented affinity for the PEG-rich phase. The PEG1500+lithium sulfate showed the highest values of partitioning coefficient. In addition, thermodynamic parameters (ΔH°, ΔS°, ΔG°) as a function of temperature, were calculated for the system PEG1500-sodium citrate at different PEG concentrations and the results imply thermodynamic differences between partitioning of CMP in this system. [Copyright &y& Elsevier]