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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item Aqueous two-phase systems of copolymer L64 + organic salt + water: Enthalpic L64–salt interaction and Othmer–Tobias, NRTL and UNIFAC thermodynamic modeling(Chemical Engineering Journal, 2011-06-15) Andrade, Vivianne Molica de; Rodrigues, Guilherme Dias; Carvalho, Raquel Moreira Maduro de; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daPhase 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 298 K) 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 −0.2 kJ mol−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: C6H5O73− > C4H4O62− > C4H4O42−. 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.Item Phase diagrams, densities and refractive indexes of poly(ethylene oxide) + organic salts + water aqueous two-phase systems: effect of temperature, anion and molar mass(Fluid Phase Equilibria, 2015-11-25) Rengifo, Andrés Felipe Chamorro; Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Silva, Maria C. Hespanhol da; Silva, Luis Henrique Mendes daThe application of aqueous two-phase systems (ATPSs) at the industrial level requires systems formed by non-toxic substances to decrease the negative impact on the environment. Organic salts such as sodium citrate, sodium tartrate and sodium succinate have been utilized in order to fulfill this objective. In this work, ATPSs formed by poly(ethylene oxide), PEO, with molar mass 10,000 or 35,000 g mol^−1, organic salts and water, namely PEO10000 + sodium citrate + water, PEO10000 + sodium tartrate + water, PEO10000 + sodium succinate + water and PEO35000 + sodium citrate + water ATPSs at (283.15, 298.15 and 313.15) K have been studied. Effects of temperature, anion and polymer molar mass on the phase diagrams, as well as, the densities and refractive indexes of both phases of the ATPSs were evaluated. The segregation process was endothermic and entropically driven for all ATPSs. The biphasic region on the phase diagrams increased as the molar mass of PEO increased. In addition, the biphasic region also increased in relation to the anions studied: citrate > tartrate > succinate. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation.Item Aqueous two-phase systems: a new approach for the determination of p-aminophenol(Journal of Hazardous Materials, 2011-08-15) Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de; Patrício, Pamela da Rocha; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol daA new method has been developed for the spectrophotometric determination of p-aminophenol (PAP) in water, paracetamol formulations and human urine samples with a recovery rate between 94.9 and 101%. This method exploits an aqueous two-phase system (ATPS) liquid–liquid extraction technique with the reaction of PAP, sodium nitroprusside and hydroxylamine hydrochloride in pH 12.0, which produces the [Fe2(CN)10]^10− anion complex that spontaneously concentrates in the top phase of the ATPS (). The ATPS does not require an organic solvent, which is a safer and cleaner liquid–liquid extraction technique for the determination of PAP. The linear range of detection was from 5.00 to 500 μg kg^−1 (R ≥ 0.9990; n = 8) with a coefficient of variation of 2.11% (n = 5). The method exhibited a detection limit of 2.40 μg kg^−1 and a quantification limit of 8.00 μg kg^−1. The ATPS method showed a recovery that ranged between 96.4 and 103% for the determination of PAP in natural water and wastewater samples, which was in excellent agreement with the results of the standard 4-aminoantipyrine method that was performed on the same samples.Item Application of hydrophobic extractant in aqueous two-phase systems for selective extraction of cobalt, nickel and cadmium(Journal of Chromatography A, 2013-03-01) Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daThis 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 (Si,j) between the metals were obtained at pH = 3.00 (SCo,Cd = 1550 and SNi,Cd = 16,700) and pH = 1.00 (SCo,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.Item Green recovery of mercury from domestic and industrial waste(Journal of Hazardous Materials, 2015-11-10) Cunha, Roselaine C. da; Patrício, Pamela R.; Vargas, Silvia J. Rodriguez; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daRecovery 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 + H2O (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 × 102 − 3.21 × 1010) 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.Item Copper recovery from ore by liquid–liquid extraction using aqueous two-phase system(Journal of Hazardous Materials, 2012-08-14) Lemos, Leandro Rodrigues de; Santos, Igor José Boggione; Rodrigues, Guilherme Dias; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol daWe 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 0.285 mmol kg−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.