Browsing by Author "Silva, Keycianne da Cruz"

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    Aqueous two-phase systems formed by different phase-forming components : equilibrium diagrams and dye partitioning study.
    (2020) Silva, Keycianne da Cruz; Abreu, Christian Silva; Vieira, Alício Wagner; Mageste, Aparecida Barbosa; Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de
    The present work aimed to characterize new aqueous two-phase system (ATPS) formed by Triton X-100 þ Li2SO4 þ H2O, polyvinylpyrrolidone Mw ¼ 10,000 g mol -1 (PVP10k) þ Li2SO4 þ H2O, and Triton X-100 þ PVP10k þ H2O, evaluating the effect of temperature and the nature of ATPS-forming components on the biphasic region. ATPSs formed by Li2SO4 showed greater efficiency in phase segregation compared to ATPSs formed by polymer/surfactant, with the biphasic area of ATPSs formed by Triton X-100 greater than that formed by PVP10k. For all ATPSs studied, temperature had a small effect on the biphasic region. The data were fitted with good correlation using the Merchuk equation for the binodal curves and OthmereTobias and Bancroft equations for the tie-lines. The partitioning studies show that there is an uneven distribution of Reactive Yellow HE-4R dye between the phases for all ATPSs and, with a tie-line length increase, there is an increase in the tendency of the dye to partition to the phase in which it interacts most strongly. For ATPSs formed by Li2SO4, the dye is preferentially transferred to the macromolecule-rich phase (top phase), whereas for the system formed by polymer/surfactant, the dye is partitioned to the PVP10k enriched phase (bottom phase). The present work aimed to characterize new aqueous two-phase system (ATPS) formed by Triton X -100 þ Li2SO4 þ H2O, polyvinylpyrrolidone Mw ¼ 10,000 g mol 1 (PVP10k) þ Li2SO4 þ H2O, and Triton X 100 þ PVP10k þ H2O, evaluating the effect of temperature and the nature of ATPS-forming components on the biphasic region. ATPSs formed by Li2SO4 showed greater efficiency in phase segregation compared to ATPSs formed by polymer/surfactant, with the biphasic area of ATPSs formed by Triton X-100 greater than that formed by PVP10k. For all ATPSs studied, temperature had a small effect on the biphasic region. The data were fitted with good correlation using the Merchuk equation for the binodal curves and OthmereTobias and Bancroft equations for the tie-lines. The partitioning studies show that there is an uneven distribution of Reactive Yellow HE-4R dye between the phases for all ATPSs and, with a tie-line length increase, there is an increase in the tendency of the dye to partition to the phase in which it interacts most strongly. For ATPSs formed by Li2SO4, the dye is preferentially transferred to the macromolecule-rich phase (top phase), whereas for the system formed by polymer/surfactant, the dye is partitioned to the PVP10k enriched phase (bottom phase).
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    Equilibrium phase behavior of aqueous two-phase system formed by triblock copolymer þ sulfate salt þ water at different temperatures.
    (2018) Gonçalves, Laryssa Fernanda da Silva; Felisberto, Nehander Carlos Mendes; Silva, Keycianne da Cruz; Mageste, Aparecida Barbosa; Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de
    Equilibrium data for the ternary liquid-liquid system formed of a triblock copolymer (L64 or F68), sulfate salts (Cu(II) or Fe(III)) and water were investigated in this work. The effects of temperature (278.15, 288.15 and 298.15 K), the nature of the cation and the copolymer molar mass on the phase diagram of the aqueous two-phase system were investigated. An increase in temperature decreased the biphasic region for the entire system. Cu(II) and F68 were better able to induce phase separation compared to Fe(III) and L64. The nature of the cation and the copolymer molar mass effect are discussed as a function of the formation of aqua acids through the reaction between the cation and water (Brønsted acids) and in relation to Flory-Huggins theory for macromolecule solutions, respectively. The consistencies of the tie line and binodal curve experimental compositions were evaluated by applying the Othmer-Tobias and Merchuk correlations, respectively.
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    Thermodynamics investigation of partition behavior of uric acid in aqueous two-phase systems.
    (2020) Gonçalves, Laryssa Fernanda da Silva; Abreu, Christian Silva; Silva, Keycianne da Cruz; Mageste, Aparecida Barbosa; Rodrigues, Guilherme Dias; Santos, Wallans Torres Pio dos; Lemos, Leandro Rodrigues de
    Uric acid (UA) is an important component in biological matrices, and the development of new methods for extracting/separating UA from several complex matrices is necessary. A viable alternative is the use of an aqueous two phase system (ATPS), which is an environmentally safe and efficient technique. In this work, an extensive study of the thermodynamic approach of UA partitioning was carried out in an ATPS formed with a polymer, sulfate salts, and water. Initially, the new ATPS formed with polyethylene glycol (400 g mol−1 ), lithium sulfate, and water was characterized by obtaining the position of the binodal curves and the phase compositions. The components’ segregation increases with the increase in the concentration of the polymer and salt where the top phase (TP) becomes richer in polymer and poorer in electrolyte, and the bottom phase has the inverse behavior. In the range of the pH studied, pH 2.40, 5.40, and 6.60 showed no effect on the binodal curve position and phase compositions, while the temperature (288.15, 298.15, and 308.15 K) evaluation indicated that the phase separation process was entropically driven. Afterward, a study of UA partitioning was carried out in several ATPSs, evaluating the effect of system composition, pH, temperature, and ATPS-forming components on the partition coefficient (K) of the UA. The K values ranged from 1.03 ± 0.04 to 6.05 ± 0.25, indicating a partition preference for the TP for all tie-line length (TLL) values. Furthermore, it is noted that the increase in TLL caused an increase in K, which decreases with increasing the temperature; that is, the partition of uric acid is temperature-dependent, and the phase transfer process of the UA is exothermic. The pH effect study showed that the ionized form of UA has a greater interaction with the components of the TP than that of the molecular form because the K value at pH 6.60 (K = 7.59 ± 0.23) is higher than at pH 2.40 (K = 1.98 ± 0.21), while at pH 5.40 (K = 3.84 ± 0.13), the value is intermediate. This behavior is due to the strong electrostatic interaction between the pseudopolycation, formed by Li+ ions plus polyethylene glycol in TP and the ionized form of UA. Finally, higher K values were obtained for the system formed with polyethylene glycol (400 g mol−1 ), lithium sulfate, and water. Thus, the balance of interactions between the system components and UA is the driving force that will drive the partition in the ATPS.