Browsing by Author "Machado, Poliana Aparecida Lopes"

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    Liquid–liquid phase equilibrium and Ion‐exchange exploration for aqueous two‐phase systems of ([C4mim] Cl+ K2CO3 or K3C6H5O7+water) at diferent temperatures.
    (2022) Machado, Poliana Aparecida Lopes; Cavalcanti, Marcello Henrique da Silva; Silva, Fábio Antônio Belinelli; Almeida, Eduardo Tonon de; Cardoso, Marcus Vinícius Cangussu; Mesquita, Anderson Fuzer; Lemes, Nelson Henrique Teixeira; Virtuoso, Luciano Sindra
    exchange were evaluated in the formation of these ATPSs. It was observed that decreasing the temperature promoted the phase separation in both ATPSs indicating the exothermic character of the process. The ability of diferent ani- ons to induce phase separation was compared and the order for the strength of the salting out efect observed was PO3− 4 > HPO2− 4 > CO2− 3 > C6H5O3− 7 ≫ HO−. The extent of ion exchange between the equilibrium phases in the two diferent ATPSs was experimentally evaluated and found to be negligible. The binodal curves were ftted to an empirical non- linear expression and the salting out efect was explored using the type-Setschenow equa- tion and the consistence of equilibrium data was evaluated theoretically using the Othmer– Tobias, Hand and Bancroft equations. Finally, the liquid–liquid equilibrium in the ATPSs evaluated in the present work were modelled by NRTL model.
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    Phase diagrams of aqueous biphasic micellar systems formed by polyethylene glycol (10,000 or 35,000 g mol -1 ) + triton x-100 + water at different temperatures : experimental and correlation.
    (2020) Machado, Poliana Aparecida Lopes; Alves, Ana Paula Pereira; Costa, Éderson D’Martin; Mageste, Aparecida Barbosa; Silva, Jose Mauricio Schneedorf Ferreira da; Virtuoso, Luciano Sindra
    A wide characterization of the phase equilibrium involved in aqueous biphasic micellar systems (ABMSs) formed by 10,000 or 35,000 g mol−1 polyethylene glycol (PEG) + t octylphenoxypolyethoxyethanol (Triton X-100) + water was evaluated at 283.15, 298.15, and 313.15 K, respectively. The influences of temperature, polymer molar mass, and mixture compositions on the phase diagrams obtained were evaluated. The analysis of the phase diagrams obtained experimentally showed that the increase of temperature favors, significantly, the phase separation process. The increase in the polymer molecular weight from 10,000 to 35,000 g mol−1 has an even more pronounced effect than that of temperature in inducing phase separation. The experimental liquid−liquid equilibrium (LLE) data were then theoretically correlated using the extended Flory−Huggins lattice model for ternary mixtures. The interaction parameters of the component’s pairs PEG−Triton X-100 (λ12), PEG−water (λ13), and Triton X-100−water (λ23) in the ABMSs were estimated at different temperatures and in two different surfactant configurations (single molecule and micellar aggregates). Although it was not possible to correlate the parameters of interaction with the physical reality of ABMSs, the Flory−Huggins model allowed to recover the LLE data within the experimental error range. The experimental data of the binodal curves for the different ABMSs were also adjusted through the Othmer−Tobias, Bancroft, and Setschenow empirical equations.
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    Thermodynamic investigation of the aqueous two-phase systems formed by PEG 400 + water + either sodium carbonate or potassium carbonate at different temperatures : experimental and correlational approaches.
    (2019) Carvalho, Roberta de Almeida; Penido, Jussara Alves; Lobo, Fabiana Aparecida; Machado, Poliana Aparecida Lopes; Lemes, Nelson Henrique Teixeira; Virtuoso, Luciano Sindra; Lemos, Leandro Rodrigues de; Rodrigues, Guilherme Dias; Mageste, Aparecida Barbosa
    Systems composed of poly(ethylene)glycol (PEG 400) + water + either potassium carbonate or sodium carbonate were studied at 283.15, 298.15, and 313.15 K. The effects of temperature and the electrolyte on phase segregation were evaluated. The phase segregation process was endothermic and entropically driven. The efficacy of the cations in inducing phase formation with PEG 400 followed the order K2CO3 < Na2CO3. The binodal curves were successfully described using the empirical equation suggested by Merchuk and modified to include the effect of temperature. Tie-line compositions were correlated using the Othmer–Tobias, Bancroft, and Hand equations. The experimental tie-line data for PEG 400 + K2CO3 + water and PEG 400 + Na2CO3 + water were also correlated using the nonrandom two liquid model. The use of this thermodynamic model resulted in reliable data for the system while reducing the number of experiments needed. All of the correlations indicated satisfactory fits between the calculated and experimental data.