Browsing by Author "Bruziquesi, Carlos Giovani Oliveira"

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    Capture of CO2 by vermiculite impregnated with CaO.
    (2022) Pereira, Matheus Henrique Simplício; Santos, Cláudio Gouvêa dos; Lima, Geraldo Magela de; Bruziquesi, Carlos Giovani Oliveira; Oliveira, Victor de Alvarenga
    Vermiculite samples were impregnated with different amounts of calcium oxide by the con- ventional thermal heating technique and subject to CO2 capture experiments in thermal analysis equipment. The amount of CO2 captured by calcium oxide increased from 13 g of CO2 per mol of CaO to 16.8 g of CO2 per mol of CaO when the experiments were carried out with pure calcium oxide and vermiculite impregnated with CaO (1:1), respectively. Integral isoconversional methods of Kissinger-Akahira-Sunose (KAS) and Osawa-Flynn-Wall (OFW) were used for the kinetic study of the process and good correlation coefficients were achieved. The apparent activation energy values showed that for low conversions (a < 0.3) the controlling step of the process is a mixed step where the chemical reaction and the dif- fusion of the reagents into the vermiculite have rates of the same order of magnitude (20 kJ < Ea < 40 kJ). For higher conversions values (a > 0.3) the apparent activation energy values suggest that the slow step is a chemical step (Ea> 40 kJ).
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    Electrocatalytic performance of different cobalt molybdate structures for water oxidation in alkaline media.
    (2018) Rodriguez, Mariandry del Valle Rodriguez; Stolzemburg, Matheus Cata Preta; Bruziquesi, Carlos Giovani Oliveira; Silva, Adilson Cândido da; Abreu, Cíntia Grossi de; Siqueira, Kisla Prislen Félix; Oliveira, Luiz Carlos Alves de; Pires, Maíra dos Santos; Lacerda, Lívia Clara Tavares; Ramalho, Teodorico de Castro; Dias, Anderson; Pereira, Márcio César
    Cobalt molybdates with different crystalline structures, i.e., α, β, and hydrated (H)-CoMoO4, were synthesized, and their electrocatalytic activities were thoroughly examined for catalyzing the oxygen evolution reaction (OER) in alkaline media. The material characteristics were associated with the electrocatalytic properties by evaluating the CoMoO4 crystal structures (XRD and Raman), morphologies (TEM), and electrochemical features (electrochemically active surface area, roughness factor, electrochemical impedance, Tafel analysis, and controlled-current electrolysis). These combined findings revealed that the electrocatalytic performance is greatly influenced by the crystalline structures of CoMoO4, following the order α-CoMoO4 > H-CoMoO4 > β-CoMoO4. The H-CoMoO4 catalysts crystallized in the triclinic space group, P[1 with combining macron] (#2), with Z = 4. On the other hand, the α- and β-CoMoO4 catalysts exhibited a monoclinic structure, C2/m (#12), with Z = 8. In the OER experiments, α-CoMoO4 showed an overpotential of 0.43 ± 0.05 V compared to the 0.51 ± 0.05 V and 0.56 ± 0.04 V exhibited by the H-CoMoO4 and β-CoMoO4 catalysts, respectively, to achieve 10 mA cm−2. All CoMoO4 structures displayed stability for at least 6 h at a controlled current density of 10 mA cm−2. Finally, computational simulations indicate that the coexistence of Co and Mo ions in edge-shared octahedral sites of α-CoMoO4 may favor the interaction between the O atom of the water molecule and the metal adsorption sites due to its surface being electronically less dense than β- and H-CoMoO4 surfaces, thus resulting in its higher performance for OER.
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    Estudo fotoeletroquímico do CuBi2O4 modificado com cobalto para produção de hidrogênio via clivagem da água.
    (2018) Bruziquesi, Carlos Giovani Oliveira; Silva, Adilson Cândido da; Pereira, Márcio César; Silva, Adilson Cândido da; Afonso, André Santiago; Dias, Anderson
    Denominado de kusachiite, o mineral de p-CuBi2O4 (CBO) possui um band-gap óptico entre 1,5-1,8eV e uma densidade de fotocorrente teórica máxima de 19,7- 29,0 mA.cm-2, além das energias das bandas de valência e condução favoráveis à oxidação da água e consequente produção de hidrogênio. Todavia, a sua baixa densidade de fotocorrente e fotocorrosão (típica em óxidos) o impossibilita de ser empregado como fotocatodo para produção de energia. Dentre as técnicas de deposição utilizadas, a de spray pyrolysis mostrou-se a melhor para a obtenção de filmes mecanicamente estáveis e uniformes (qualidades essas imprescindíveis para se alcançar reprodutibilidade). Sintetizado in situ sobre o substrato de vidro FTO utilizando spray pyrolysis, variando condições como: solvente, tempo de calcinação, temperatura e espessura da camada depositada, fora alcançada uma densidade de fotocorrente superior à literatura (−2.5 mA.cm-2 a 0.6 V vs RHE em H2O2) 1. No entanto, a problemática da fotocorrosão persistiu, sendo necessário um estudo mais detalhado a respeito do transporte de cargas minoritárias à interface semicondutor-eletrólito. Este trabalho apresenta uma melhora na eficiência em correntes catódicas e instabilidade fotoquímica quando empregada a dopagem de Co2+. Nesses filmes preparados utilizando 3% de Co, não fora observada a fotorredução do material quando estudados em 0,5 M de Na2SO4 (pH~7), sob fonte de Xe (A.M 1,5G) a um potencial de -0,6V vs. Ag/AgCl, atingindo em média, uma densidade de fotocorrente igual a -2,5 mA.cm-2. Valor esse superior ao encontrado em outros trabalhos. Pode-se inferir que a dopagem do material utilizando Co mostrou-se uma alternativa para evitar a fotorredução. Espera-se que este trabalho contribua para o melhoramento da estabilidade do p-CuBi2O4 para aplicação em células fotoeletroquímicas.
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    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 do
    New 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.
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    Nióbio : um elemento químico estratégico para o Brasil.
    (2020) Bruziquesi, Carlos Giovani Oliveira; Gabriel Filho, José Balena; Pereira, Márcio César; Silva, Adilson Cândido da; Oliveira, Luiz Carlos Alves de
    Niobium, in fact, is an essential element for Brazil. Their applications are so many and so special that they put it as one of the subjects treated by the wikiLeaks site as strategic and that it should be treated in the USA. It is one of the elements most exported by Brazil and is mainly used in the production of special alloys for use in gas pipelines, air turbines, among other applications. It is believed that niobium-based materials can be obtained for applications with higher added value and in equally strategic areas. Research to obtain active and selective drugs, materials to maximize the use of renewable energy, and new nanostructured materials to improve the performance of different components are ongoing and promise a revolution for the next few years.
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    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 da
    In 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.