Browsing by Author "Rezende, Jaqueline de Paula"

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    Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon : a thermodynamic study.
    (2017) Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hespanhol, Maria C.; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Gurgel, Leandro Vinícius Alves; Silva, Luis Henrique Mendes da
    Carbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye (ΓD) increased in the order ΓD (PR) < ΓD (AR) < ΓD (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed (ΓD,max) reached values of up to 2.00 μmol m−2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (ΔadsH) and entropy change (TΔadsSref) values were higher than −137.0 kJ mol−1 and −114.2 kJ mol−1, respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces.
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    A simple and inexpensive thermal optic nanosensor formed by triblock copolymer and polydiacetylene mixture.
    (2018) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Ortega, Paulo Fernando Ribeiro; Silva, Luis Henrique Mendes da
    Polydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (Ttr) to as low as 24 °C. When using different TCs, the Ttr values can be ordered as L35 < F68< L64 < F127