Browsing by Author "Virtuoso, Luciano Sindra"

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    Comportamento de fase e aspectos interacionais de sistemas aquosos bifásicos formados por sais de tiocianato e surfactante não iônico triton X.
    (2022) Gonçalves, Gessyca Rosa Silva; Ferreira, Gabriel Max Dias; Cardoso, Marcus Vinícius Cangussu; Ferreira, Gabriel Max Dias; Cardoso, Marcus Vinícius Cangussu; Patino Agudelo, Alvaro Javier; Virtuoso, Luciano Sindra
    Neste trabalho foram obtidos dados de equilíbrio líquido-líquido para sistemas aquosos bifásicos (SABs) formados por surfactante não iônico triton X (triton X-165 ou triton X- 305) + sal (tiocianato de sódio (NaSCN), tiocianato de amônio (NH4SCN) ou tiocianato de potássio (KSCN) + água, em diferentes temperaturas (298,2, 313,2 e 328,2 K). Os diagramas de fase dos SABs investigados foram obtidos pelo método de quantificação das fases, sendo discutidos os efeitos da mudança de temperatura, do aumento da cadeia hidrofílica do surfactante e da mudança do cátion formador do sal sobre os dados de equilíbrio. Além disso, aspectos interacionais associados com as propriedades dos SABs foram discutidos a partir dos dados de equilíbrio e de análises de RMN. Para os SABs formados com NaSCN ou KSCN, constatou-se que a fase superior foi rica em surfactante (wTX ≥ 25,43% m/m), ao mesmo tempo em que apresentou elevada concentração de sal (wsal ≥ 26,50% m/m), enquanto a fase inferior foi rica em sal (wsal ≥ 35,45% m/m) e com concentrações de surfactante próximas de 0% m/m. Por outro lado, nos SABs formados com NH4SCN foi verificado uma inversão de fase, em que a fase superior passou a ser a fase rica em sal (wsal ≥ 47,59% m/m) e a fase inferior passou a ser a fase rica em surfactante (wTX ≥ 28,63% m/m), com esta última também contendo elevadas concentrações de sal. Foi observado que o tamanho da região bifásica dependeu do cátion formador do sal e aumentou na ordem: K+ > Na+ > NH4 + . Além disso, o aumento da temperatura promoveu um leve aumento da região bifásica dos SABs, sendo a magnitude desse efeito maior no sistema formado por NaSCN. Foi verificado que o surfactante TX– 305 foi mais eficiente para induzir a separação de fases que o surfactante TX–165, sendo este efeito atribuído à maior massa molar do TX–305. Além disso, verificou-se que para determinadas condições termodinâmicas, os SABs formados com NaSCN apresentaram a capacidade de formar sistemas com uma fase líquida em equilíbrio com uma fase de aspecto de gel. A partir dos resultados de RMN, pode-se inferir que a capacidade relativa de indução de fase foi associada ao efeito combinado do cátion com o ânion SCNsobre a estrutura da água, em que a combinação do cátion NH4 + com aqueles ânions é mais eficiente para diminuir a contribuição entrópica que induz o sistema a se separar em duas fases. Os resultados obtidos trazem avanços e perspectivas relevantes para estudos que visem à compreensão dos processos que regem a formação de SABs baseados em surfactantes não iônicos.
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    How does the use of surfactants in polymer-salt based aqueous twophase systems affect the annatto dye (Bixa orellana L.) partitioning?
    (2018) Junqueira, Cristina Mazzeu; Cabral, Deliane da Silva; Penido, Jussara Alves; Mageste, Aparecida Barbosa; Virtuoso, Luciano Sindra
    In this work, the partitioning of natural annatto pigments in aqueous two-phase systems formed by poly(ethylene) glycol polymers (1500 or 4000 or 6000 g mol−1) or triblock copolymer L35 (2000 g mol−1) + sodium citrate + water was studied in the presence of cetyltrimethylammonium bromide. The hypothesis investigated was that the use of surfactants as additives in traditional two-phase aqueous systems could improve the solubility of the annatto extract in the phases of these systems through a mechanism of mixed micelle formation. This would make it possible to implement the use of these systems in the annatto dye extraction process. For this, several experiments were conducted. The annatto extract partition coefficient was determined as a function of pH, surfactant concentration, molar mass and hydrophobicity of the polymer, tie-line length, and the nature of the electrolyte. These results showed the potential of surfactant as a modulation agent for dyes transfer between the aqueous two-phase systems phases. The effect of surfactant was attributed to its interaction with norbixin from annatto, which was studied by means of surface tension and spectrophotometric measurements. The driving force governing annatto extract partitioning was dependent on the system composition and the temperature. Lower partition constants values for annatto extract obtained in the presence of surfactant demonstrated the potential of the aqueous two-phase systems for the extraction or purification of annatto.
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    Layered double hydroxides for remediation of industrial wastewater containing manganese and fluoride.
    (2018) Teixeira, Mariana Araujo; Mageste, Aparecida Barbosa; Dias, Anderson; Virtuoso, Luciano Sindra; Siqueira, Kisla Prislen Félix
    This work describes an environmentally-friendly procedure for the removal of manganese and fluoride from industrial wastewaters (IW) using layered double hydroxides (LDHs) and calcined layered double oxides (LDOs). Ternary Mg-Mn-Al LDHs (LDH-IW) were produced from IW containing a high concentration of manganese, which decreased from (99.420 ± 3.110) mg L 1 to (0.003 ± 0.001) mg L 1 after the synthesis procedure. Synthetic Mg-Al LDH was also produced for comparison purposes. Both materials were calcined and the resulting oxides (LDO and LDO-IW) were used for the removal of fluoride present in the same IW. The materials were characterized by X-ray diffraction, electron energy-loss spectroscopy, thermal analysis, Raman spectroscopy, and electron microscopy. The kinetics and adsorption isotherms for fluoride removal from aqueous solutions were studied in batch mode. For both LDO and LDO-IW, the adsorption of fluoride followed pseudo-second order reaction kinetics. Langmuir-type adsorption was observed for LDO, while adsorption by LDO-IW was according to the Freundlich model. The results showed that the oxides were able to remove 94% of the fluoride present in the IW at an initial concentration of 162 mg L 1. The procedure reduced the concentrations of the pollutants (manganese and fluoride) to levels that complied with Brazilian effluent standards.
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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.