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Abstract: The partitioning behavior of the [Fe(CN)5(NO)]2− and [Fe(CN)6]3− anions were studied in aqueous two-phase systems (ATPS) formed by potassium phosphate and macromolecules—poly(ethylene oxide) (1500gmol−1) and triblock copolymers, PEO–PPO–PEO, where PEO and PPO are poly(ethylene oxide) and poly(propylene oxide), respectively. Two copolymers with different hydrophobicity were used, L35 (50% EO and 1900gmol−1) and F68 (80% EO and 8400gmol−1). The partition coefficient for the [Fe(CN)5(NO)]2− and [Fe(CN)6]3− anions in each ATPS were investigated as a function of the temperature, tie-line length and phases hydrophobicity. The relative order of the partition coefficient is L35

Abstract: This work developed a new and efficient method of extracting and separating Co(II), Ni(II) and Cd(II) in aqueous two-phase systems (ATPS) composed of triblock copolymer (L64)+Na2C4H4O6 +water and L64+Li2SO4 +water using the hydrophobic extractant 1-nitroso-2-naphtol, which complexes the metal ions and partitions in the triblock copolymer micelles in the ATPS top phase. Metal extraction from the salt-rich phase to the copolymer – rich phase is strongly affected by the fine-tuning of the following parameters: amount of added extractant, type of electrolyte, pH, and tie-line length. Excellent separation factors (S i,j) between the metals were obtained at pH = 3.00 (S Co,Cd = 1550 and S Ni,Cd = 16,700) and pH = 1.00 (S Co,Ni = 826). In the interference study, Co(II) was selectivity extracted in the top phase in the presence of Ni(II) and Cd(II) in a concentration of up to 20 times the cobalt level in the system. [Copyright &y& Elsevier]

Abstract: A greener and more sensitive spectrophotometric procedure has been developed for the determination of phenol and o-cresol that exploits an aqueous two-phase system (ATPS) using a liquid–liquid extraction technique. An ATPS is formed mostly by water and does not require organic solvent. Other ATPS components used in this study were the polymer, polyethylene oxide, and some salts (i.e., Li2SO4, Na2SO4 or K2HPO4 +KOH). The method is based on the reaction between phenol, sodium nitroprusside (NPS) and hydroxylamine hydrochloride (HL) in an alkaline medium (pH 12.0), producing the complex anion [Fe2(CN)10]10− that spontaneously concentrates in the top phase of the system. The linear range was 1.50–500μgkg−1 (R ≥0.9997; n =8) with coefficients of variation equal to 0.38% for phenol and 0.30% for o-cresol (n =5). The method yielded limits of detection (LODs) of 1.27 and 1.88μgkg−1 and limits of quantification (LOQs) of 4.22 and 6.28μgkg−1 for phenol and o-cresol, respectively. Recoveries between 95.7% and 107% were obtained for the determination of phenol in natural water and wastewater samples. In addition, excellent agreement was observed between this new ATPS method and the standard 4-aminoantipyrine (4-AAP) method. [Copyright &y& Elsevier]

Abstract: 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). [Copyright &y& Elsevier]

Recovery of mercury from effluents is fundamental for environmental preservation. A new, green method was developed for separation of mercury from effluent containing different metals. The extraction/separation of Hg(II) was studied using aqueous two-phase system (ATPS) comprising by polyethylene oxide (PEO1500) or triblock copolymers (L64 or L35), electrolyte (sodium citrate or sodium sulfate) and water in the presence or absence of chloride ions. The extraction behavior of the Hg(II) for the macromolecule-rich phase is affected by the following parameters: amount of added extractant, pH, and the nature of the electrolyte and macromolecule of the ATPS. The APTS of PEO1500 + sodium citrate + H 2 O (pH 1.00 and 0.225 mol kg −1 KCl) produced the highest Hg(II) % E = (92.3 ± 5.2)%. Under the same conditions, excellent separation factors (1.54 × 10 2 − 3.21 × 10 10 ) for recovery of mercury in the presence of co-existing metals were obtained. Efficient and selective extraction of Hg(II) from domestic and industrial synthetic effluents was achieved using this ATPS. [ABSTRACT FROM AUTHOR]

Partitioning behavior of the whey proteins a-lactalbumin (α-la) and β-lactoglobulin (β-lg) in aqueous two-phase systems prepared with poly ethylene glycol (PEG) and sodium polyacrilate (NaPA) was investigated as a function of pH and polymer concentrations. It was observed that α-la concentrated in the PEG phase while β-lg concentrated in the NaPA phase. Response surface methodology was applied to optimize protein partitioning and to achieve the best conditions for their fractionation. Thermodynamic analysis based on isothermal titration microcalorimetry indicated that the partitioning of α-la was accompanied by endothermic heat and was entropically driven, while β-lg partitioning was accompanied by exothermic heat and was enthalpically driven at low polymer concentrations and entropically driven at high polymer concentrations. Purification and yield parameters were determined using fresh whey and the results allowed for conclusion of the great applicability of this new system for α-la and β-lg fractionation. [ABSTRACT FROM AUTHOR]

Highlights: [•] A green and low cost technique for metal separation was discovered. [•] Aqueous two-phase system (ATPS) is predominantly composed by water. [•] ATPS is an efficient substitute for liquid-liquid extraction using organic solvent. [•] Excellent separation factor for Cu and Zn was obtained. [Copyright &y& Elsevier]

Abstract: We investigated the extraction behavior of Cu(II) in the aqueous two-phase system (ATPS) formed by (L35+MgSO4 +H2O) or (L35+(NH4)2SO4 +H2O) in the presence of the extracting agent 1-(2-pyridylazo)-2-naphthol (PAN). At pH=3 and a PAN concentration of 0.285mmolkg−1, both ATPS lead to the effective separation of Cu(II) from other metallic ions (Zn(II), Co(II), Ni(II) and Fe(III)). High separation factors range between 1000 and 10,000 were obtained for the extraction of Cu(II) and concomitant metallic ions. This ATPS was used for the extraction of Cu(II) from a leached ore concentrate with a extraction percentage of 90.4±1.1%; other metals were mainly located in the bottom phase. [Copyright &y& Elsevier]

Abstract: Phase diagrams of two-phase systems (ATPS) composed by the triblock copolymer L64+organic salt (sodium tartrate, sodium succinate, sodium citrate, or ammonium citrate)+water, at different temperatures (278, 288, and 298K) are presented in this work. Contrary to behavior of ATPS formed by inorganic salts, the study of the temperature influence in the liquid–liquid equilibrium behavior of L64–organic salts ATPS showed an exothermic character for phase separation process. Microcalorimetric measurements showed that this phase separation energy is around −0.2kJmol−1 for all organic salts. The module of slope of tie line (STL) tends to increase with an increase in temperature. The cation nature effect showed that the salt Na3C6H5O7 was more effective in promoting phase separation than (NH4)3C6H5O7. The capacity of the different anions tested for inducing ATPS formation with L64 followed the order: C6H5O7 3− >C4H4O6 2− >C4H4O4 2−. Because the salt–L64 interaction energy to be very similar, the cation and anion effects on the phase separation could be attribute to a process driven by entropy. The interaction parameters of the NRTL and UNIFAC models were estimated through the experimental data of all ternary systems. The results of the NRTL (with 64 tie-lines) and UNIFAC (with 27 tie-lines) were considered excellent with global root mean square deviations, respectively, of the 1.04% and 0.87%. The consistencies of the all tie-line experimental compositions were improved by applying the Othmer–Tobias correlation. [Copyright &y& Elsevier]

Abstract: The separation of Cd and Ni from Ni–Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li2SO4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2±3.1)% and Ni (10.6±0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00mmolkg−1, mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds. [Copyright &y& Elsevier]