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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]

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]

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: 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: 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: 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]