Navegando por Autor "Xavier, Farlon Felipe Silva"
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Item New synthesis method for a core-shell composite based on α-Bi2O3@PPy and its electrochemical behavior as supercapacitor electrode.(2019) Xavier, Farlon Felipe Silva; Bruziquesi, Carlos Giovani Oliveira; Fagundes, Wélique Silva; Matsubara, Elaine Yoshiko; Rosolen, Jose Mauricio; Silva, Adilson Cândido da; Canobre, Sheila Cristina; Amaral, Fábio Augusto doNew composite based on polypyrrole (PPy) and bismuth oxide (α-Bi2O3) was investigated as supercapacitor electrode. The α-Bi2O3 was obtained by hydrothermal route at 500 °C for 2 h. Cyclic voltammetry was used to electropolymerize PPy on graphite electrode (GE) or on GE/α-Bi2O3. The X-ray diffraction profile of Bi2O3 revealed the α-Bi2O3 monoclinic structure with space group P21/c. The scanning and transmission electron microscopy images showed that PPy coated α-Bi2O3. Raman spectra showed that PPy inhomogeneously coated α-Bi2O3, but it was still possible to obtain a α-Bi2O3@PPy core-shell hybrid composite with highly ordered α-Bi2O3 with electronic interaction between the oxide and the polymer chain of the polymer. The GE/α-Bi2O3@PPy composite electrode (type I supercapacitor) displayed a predominantly capacitive profile with low impedance values and good electrochemical stability after 50 charge and discharge cycles. The specific capacitance of α-Bi2O3@PPy composite was found in the range of 634 to 301 F g-1 to gravimetric current of 3 and 10 A g-1, respectively.Item Removal of sodium diclofenac from aqueous medium using layered double hydroxide : a thermodynamic and theoretical approach.(2022) Bruziquesi, Carlos Giovani Oliveira; Xavier, Farlon Felipe Silva; Pacheco, Ingrid da Silva; Amaral, Fábio Augusto do; Canobre, Sheila Cristina; Gonçalves, Mateus A.; Ramalho, Teodorico de Castro; Martínez Saavedra, Liz Nayibe; Gurgel, Leandro Vinícius Alves; Silva, Adilson Cândido daIn this study, an adsorbent based on layered double hydroxide (Co–Al–NO3]-LDH) was synthesized by the co-precipitation method at constant pH 8.0±0.5. This new material was used for the removal of diclofenac from water. The X-ray difraction pattern of [Co–Al–NO3]-LDH revealed a basal spacing of 0.859 nm. Equilibrium time was reached after 120 min for an initial concentration (C0) of diclofenac of 500 mg L−1, and the pseudo-second order model best ftted the kinetic data obtained at C0 values of 100, 250, and 500 mg L−1. The isotherms performed at 15, 25, 35, and 45 °C showed an increase in the maximum adsorption capacity (Qmax=494.9 mg g−1) up to 25 °C, but at temperatures above 25 ºC, the Qmax value was not increased. Equilibrium data were ftted using the Langmuir, Freundlich, and Sips models, and the change in standard free energy of adsorption was estimated from the Langmuir constant, corrected for the equilibrium activity coefcient, while the changes in standard enthalpy and entropy of adsorption were calculated from the van’t Hof equation. Adsorption studies as a function of nitrate concentration at two C0 values (50 and 500 mg L−1) showed that the increase in nitrate concentration led to a decrease in the Qmax of diclofenac, showing that nitrate competes with diclofenac for the adsorption sites. Theoretical studies were carried out using four diferent confgurations of the diclofenac molecule approaching the surface of [Co–Al–NO3]-LDH. The interaction distance between diclofenac and [Co–Al–NO3]-LDH of 2.0 Å presented the lowest energy.