Browsing by Author "Coelho, Yara Luiza"

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    Aggregation of sodium dodecylbenzene sulfonate : weak molecular interactions modulated by imidazolium cation of short alkyl chain length.
    (2020) Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Coelho, Yara Luiza; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Ionic liquids (ILs) can modify cooperative process in aqueous solutions to a large extent, including anionic surfactant aggregation. Here, the micellization of sodium dodecylbenzene sulfonate (SDBS) was evaluated in low concentrations of 1-alkyl-3-methylimidazolium chloride (CnmimCl, n = 0, 2, and 4) aqueous solutions through fluorescence spectroscopy, isothermal titration calorimetry, dynamic light scattering, and conductometry. The thermodynamic stability of SDBS aggregates strongly depended on the IL structure and concentration, following the order C4mim+ > C0mim+ ≈ C2mim+. At 1.0 mmol L−1 of the ILs, the increase of the hydrophobicity of the imidazolium cation decreased the enthalpic favorableness, changing from −3.75 ± 0.07 kJ mol−1, for C0mim+, to −2.69 ± 0.01 kJ mol−1, for C4mim+. On the other hand, the entropic feasibility showed an opposite trend, i.e., the higher hydrophobicity of C4mim+ overcame the kosmotropic effect of IL cations in the bulks. We suggested that the imidazolium cations interact with the SDBS monomers on the micellar surface, mainly through hydrophobic, π-π, and electrostatic interactions for C4mim+ and C2mim+, and through electrostatic interactions and hydrogen bonds for C0mim+.
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    Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution.
    (2021) Gonçalves, Fernanda Jorge; Gurgel, Leandro Vinícius Alves; Soares, Liliane Catone; Teodoro, Filipe Simões; Ferreira, Guilherme Max Dias; Coelho, Yara Luiza; Silva, Luis Henrique Mendes da; Prim, Damien; Gil, Laurent Frédéric
    The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g− 1 for Cu(II) and 3.86 and 0.98 mmol g− 1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re- adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.
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    New insights into the partitioning of phenothiazine dyes in aqueous two-phase systems.
    (2020) Coelho, Yara Luiza; Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Castro, Alan Stampini Benhame de; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Aqueous two-phase systems (ATPSs) have proven to be efficient and environmentally safe methods for extracting chemical species. However, the driving forces behind the partition of solutes in these systems are still little understood. A complete thermodynamic partitioning of phenothiazine dyes was investigated in poly(ethylene oxide) (PEO) + salt + water ATPSs. Standard transfer parameters (Gibbs free energy change (ΔtrGo ), enthalpy change (ΔtrHo ) and entropy change (TΔtrSo )) were evaluated, and their dependence on the dye structure, electrolyte nature and tie line length (TLL). All phenothiazine dyes are concentrated predominantly in the polymer enriched phase, with ΔtrGo values ranging from −4.1 up to −13.4 kJ mol−1. Due to the dye-PEO attractive interactions that occur mainly via benzene condensed ring present in the structures of phenothiazine dyes, the partitioning of these dyes was enthalpically driven, with −11.4 ≥ ΔtrHo ≥ −52 kJ mol−1 and −4.93 ≥ TΔtrSo ≥ −38 kJ mol−1.
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    Solvophobic effect of 1-alkyl-3-methylimidazolium chloride on the thermodynamic of complexation between β-cyclodextrin and dodecylpyridinium cation.
    (2019) Patino Agudelo, Alvaro Javier; Coelho, Yara Luiza; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes da
    Preferential solvation participate in various supramolecular self-assembly processes, whose thermodynamic properties can be modulated by the addition of ionic liquids (ILs). However, the effects of these liquids on the thermodynamics of the host-guest complexation process remain unexplored. In this study, the thermodynamic properties of the complexation between 1-dodecylpyridinium cations (C12Py+) and β-cyclodextrin (βCD) species in aqueous solutions with different concentrations of 1-alkyl-3-methylimidazolium halides (CnmimX) were investigated by isothermal titration calorimetry. In water, C12Py+ and βCD form a 1:1 inclusion complex, which is enthalpically ( −9.2 ± 0.1 kJ mol−1) and entropically ( 16.1 ± 0.2 kJ mol−1) favorable. However, in IL aqueous solutions, all the βCD―C12Py+ thermodynamic parameters of the complexation change and this IL effect is dependent on the carbon chain length of Cnmim+ cations. ILs with shorter alkyl chains (Cnmim+, n ≤ 4) decreases the system entropy, while ILs with longer alkyl chains (Cnmim+, n ≥ 6) reduce the enthalpy values. These effects are attributed to i) preferential solvation of surfactant tails by ILs; ii) ability of the ILs to modify the 3D water structure and iii) inclusion of IL molecules into the inner cavities of βCD.