Mestrado em Química
URI Permanente para esta coleção
Nível: Mestrado Acadêmico
Ano de início: 2006
Conceito atual na CAPES: 5
Ato normativo: Homologação da 85ª Reunião do CTC-ES, Parecer CNE/CES nº 163/2005.
Processo nº 23001.000081/2005-56 do Ministério da Educação.
Publicado no DOU 28/07/2005, seção 1, página 11)
Periodicidade de seleção: Anual
Área(s) de concentração: Química
Url do curso: https://quimica.vitoria.ufes.br/pt-br/pos-graduacao/PPGQ/detalhes-do-curso?id=954
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- ItemDesenvolvimento de eletrocatalisadores metálicos de baixo custo (Ni, Cu e Zn) para redução de CO2(Universidade Federal do Espírito Santo, 2025-01-30) Barcelos, Marcela Miranda; Ribeiro, Josimar; https://orcid.org/0000-0002-9544-1647; http://lattes.cnpq.br/1265145498501171; https://orcid.org/0009-0000-4612-0524; Rosa, Thalles Ramon; https://orcid.org/0000-0001-9913-5885; http://lattes.cnpq.br/2629035369494897; Luz, Priscilla Paiva; https://orcid.org/0000-0002-9460-546X; http://lattes.cnpq.br/3663470249824660Due to a series of environmental problems resulting from the burning of fossil fuels, it has led to an increase in CO2 emissions into the atmosphere, and it is clear that alternatives need to be considered. For example, electrochemical reduction of CO2 (RECO2) appears as a promising alternative to mitigate the impacts of high CO₂ emissions into the atmosphere. Therefore, the objective of this work is to investigate the metallic electrocatalysts of Cu, Ni and Zn for electrochemical reduction of CO2. In order to characterize morphological modifications of the metallic electrodes, X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) techniques were used. The results of the XRD analyses revealed that the surface treatments did not alter the structure of the materials. The electrochemical polishing process of copper led to a mostly homogeneous morphology. On the other hand, the ultrasonic process in organic solvent allowed the increase of the roughness of the nickel and zinc electrodes, obtaining a heterogeneous morphology due to the surface reorganization of the materials. The electrochemical studies were performed using Linear Scanning Voltammetry (LSV), the potentiodynamic polarization technique and Electrochemical Impedance Spectroscopy (EIS). The EIS was performed at two different potentials: −0.4 V and −0.6 V vs. Ag/AgCl. The EIS results allowed the identification of substantial changes that occurred before and after the treatment of the electrodes. For the Cu and Ni electrodes, the EIS data indicate greater kinetics, i.e., lower charge transfer resistance. For the Zn electrode, the results indicate that there was competition in the hydrogen evolution reaction (HER). The LVS showed that the Cu and Ni electrodes showed a high current density for the electrochemical reduction reaction of CO2. It was observed that the uniform metallic copper surface acts as an inhibitor of the HER, resulting in a decrease in the overpotential and an increase in the current density for the CO2 reduction reactions. The nuclear magnetic resonance results obtained after the chronoamperometry experiments (constant potential of −2.0 V vs. Ag/AgCl in K2CO3 0.5 mol L–1 for 2 h) indicated the formation of some products from RECO2 such as: ethane, acetone and acetate. These results demonstrate the great potential of these electrocatalysts for the electrochemical reduction of CO2.
- ItemDesenvolvimento de biocompósito à base de amido de mandioca e fibras de eucalipto modificadas com nanopartículas de prata(Universidade Federal do Espírito Santo, 2025-03-19) Santos, Luisa Borges dos; Machado, Marta Albuquerque; https://orcid.org/0000-0001-8335-3351; http://lattes.cnpq.br/5991893415892784; https://orcid.org/0009-0001-9653-5186; http://lattes.cnpq.br/3784351753717889; Silva, Marcelo Henrique Prado da; Silva Filho, Elói Alves daThis study describes the production of a thermoplastic starch-based (ATP) biocomposite reinforced with eucalyptus fibers (FE) chemically treated and modified with silver nanoparticles by thermocompression technique. The fibers were subjected to an alkaline process, followed by bleaching by hydrogen peroxide. To investigate the particle size effect of the reinforcing fibers, biocomposites containing 20 %(w/w) fibers in the particle size ranges of 75–250 𝜇m (ATP/FE75), 250–600 𝜇m (ATP/FE250) e 600–1800 𝜇m (ATP/FE600) were prepared. Then, the effect of the reinforcement load content (5, 10, 20 and 30 %w/w) was evaluated, maintaining the fixed particle size (600–1800 μm). Finally, silver nanoparticles were incorporated into the bleached fibers and the biocomposite (ATP/Ag@FE) containing the modified fibers was prepared in order to evaluate the influence of the modification. The treated fibers were analyzed by Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) to evaluate changes in the composition of the fibers and their crystal structure. All biocomposite samples formulated in this study were characterized by scanning light and electron microscopy, tensile tests, moisture absorption, and swelling. The sorption capacity of the biocomposites in petroleum/water emulsion was also evaluated. Micrographs revealed a higher matrix-fiber adhesion for the ATP/FE600 sample, which resulted in a 30% increase in maximum tensile strength, 63 % in tensile modulus and a 27 % reduction in elongation compared to the unreinforced sample. In contrast, tensile tests identified that a higher fraction of reinforcement fibers per volume of the biocomposite can impair adhesion, generating points of failure in the material. Regarding fiber content, the sample containing 10 %(w/w) showed an increase of 226 % in the maximum tensile strength and reduction of 63.9 % in elongation in relation to the sample without reinforcement. Meanwhile, samples containing 20 and 30 %(w/w) of fibers showed lower adhesion between the fiber and matrix, as evidenced by tensile tests and optical and scanning electron micrographs. In addition, surface modification with nanoparticles can improve the storage capacity of the material and can be applied to the treatment of oily emulsions, with a sorption capacity of the material of 53.8 %, and preserving the integrity of the material, slowing down the growth of microorganisms. The control of size and fraction, as well as the possibility of modifying the surface of the reinforcement material emerge as strategies to improve mechanical attributes and mitigate moisture/water absorption tendencies in starch-based biocomposites, contributing to sustainable and high-performance materials.
- ItemEstudo da alteração dos parâmetros químicos do solo pela aplicação de biocarvão de palha de café (Coffea canephora) : uma Atividade Experimental Problematizada (AEP)(Universidade Federal do Espírito Santo, 2025-03-06) Feu, Amanda Marsoli Azevedo; Luz, Priscilla Paiva ; https://orcid.org/0000-0002-9460-546X; http://lattes.cnpq.br/3663470249824660; Moura, Paulo Rogerio Garcez de; https://orcid.org/0000-0002-6893-3873; http://lattes.cnpq.br/9815585530252572; https://orcid.org/0009-0002-1051-928X; http://lattes.cnpq.br/7004723737422222; Silva, André Luís Silva da ; https://orcid.org/0000-0002-8245-9389; http://lattes.cnpq.br/0808253492421363; Athayde, Geisamanda Pedrini Brandão ; https://orcid.org/0000-0002-4315-0653; http://lattes.cnpq.br/8037324704189596This study evaluated the application of the Problematized Experimental Activity (PEA) as a didactic strategy in chemistry teaching, within an Experimental Inorganic Chemistry course for undergraduate chemistry students at the Federal University of Espírito Santo (Ufes), Brazil. The objective was to investigate how the PEA contributes to meaningful learning by integrating laboratory practices with theoretical foundations, using soil chemistry and biochar as the experimental and contextual axis. The research adopted a mixed-methods approach, combining qualitative and quantitative methods, with an experimental design for the analysis of biochars and a didactic intervention to assess student learning. Biochars produced at different pyrolysis temperatures were characterized by analyzing their elemental composition, thermal stability, and effects on soil properties. The results showed that the pyrolysis temperature directly influences the chemical and structural properties of the biochars, affecting their ability to improve soil fertility. The biochar produced at 600 °C (BC600) exhibited higher chemical stability and alkalinity, while the one produced at 350 °C (BC350) retained a greater quantity of polar functional groups. Soils treated with biochar showed an increase in pH in water from 4.58 to 5.20 and in CaCl₂ from 3.84 to 4.43; available phosphorus rose from 0.4 to 1.8 mg/dm³; calcium increased from 0.48 to 1.35 cmolc/dm³; and the sum of bases rose from 1.14 to 2.15 cmolc/dm³. Improvements in cation exchange capacity and a reduction in aluminum saturation were also observed. In the educational context, the PEA favored the mobilization of students’ prior knowledge and the construction of meanings, while also encouraging autonomy, critical thinking, and the development of metacognitive skills, although further studies are needed to confirm this effect conclusively. Participant feedback indicated that the experimental approach enhanced the understanding of chemical phenomena and reinforced the scientific contextualization of the contents. It is concluded that the integration of biochar as a soil conditioner and the PEA constitutes a promising alternative both for improving soil fertility and for chemistry teaching, by meaningfully connecting science, education, and sustainability in the training of future chemistry professionals
- ItemEstudo da otimização do método de centrifugação para análise da eficiência na extração de material interfacial em óleo emulsionado caracterizado por FT-ICR MS(Universidade Federal do Espírito Santo, 2025-03-06) Souza, Luciara Costa de; Souza, Lindamara Maria de ; https://orcid.org/0000-0002-0514-9133; http://lattes.cnpq.br/6194660060650807; Romão, Wanderson; https://orcid.org/0000-0002-2254-6683; http://lattes.cnpq.br/9121022613112821; https://orcid.org/0000-0002-8575-8982; http://lattes.cnpq.br/1475251734131608; Cunha Neto, Álvaro; https://orcid.org/0000-0002-1814-6214; http://lattes.cnpq.br/7448379486432052; Carvalho, Rogério Mesquita de; https://orcid.org/0000-0002-5908-2122; http://lattes.cnpq.br/4237474598406733Emulsions are common in the oil industry, present in various processes such as extraction, transportation and refining. However, emulsions can present a significant problem in this sector. Understanding the compounds that play a significant role in stabilizing water/oil (W/O) emulsions is crucial to developing effective treatment methods. The isolation and characterization of Interfacial Material (IM) is an attempt to better understand the species involved in the formation and stabilization of emulsions. This study aims to optimize the methodology of Pereira et al. (2014), which is based on centrifuging an emulsion and separating the oily phase from the remaining (unresolved) emulsion. The study aims to investigate the influence of time and temperature in the centrifugation step, in order to obtain the interfacial material. A sample of naturally emulsified oil was centrifuged, initially varying the centrifugation time by 15, 30, 60, 90, 120, 180, 240 minutes, keeping the temperature constant at 60 °C and the rotation at 9500 rpm. The temperature was then varied by 20, 30, 40, 50 and 60 °C, keeping the time constant at 120 minutes and the rotation at 9500 rpm. The centrifugation stage resulted in two fractions (EPS and EPR). These fractions were distilled using Dean-Stark (to remove the water), centrifuged (to remove the salt) and evaporated (to remove the solvent) to obtain the interfacial materials (IMS and IMR) respectively. All samples were analyzed using ESI(-)FT-ICR MS. High-resolution mass spectrometry proved crucial for identifying the chemical species of the oil and its fractions, as well as offering precise insights into the molecular composition of the IMS by identifying the species that contribute to the stability of the emulsion. The analysis indicated that adjusting the centrifugation time and temperature in the IMR and IMS samples resulted in a decrease in nitrogen species (N1[H] class) and an increase in naphthenic acids (ANs or O2), N2[H] species and mixed classes (N1O2[H], N1O3[H], O3[H] and O3S[H]). Notably, highly aromatic molecules with double bond equivalents (DBE) of 4 to 20 migrated from the aqueous phases to the N1O2[H] and N1O3[H] classes. For ANs, there was a migration to the interface mainly of linear (DBE 1) and aromatic (DBE > 11) molecules. The increase in aromaticity of the IMR sample compared to the crude oil emulsion was confirmed by means of Van Krevelen diagrams, where the H/C vs. O/C or N/C ratio showed a decrease in H/C values for NxOy[H], Oy[H] and Nx[H] species, with x = 1-2 and y = 1-3. The application of Principal Component Analysis (PCA) to the MS data allowed the classification of emulsions based on the type of fraction produced by centrifugation MI, EPR, EPS, crude oil and dehydrated crude oil. The main classes of compounds driving the PCA variance for the MI class were N1O1[H], N1O2[H], N1O3[H], O2[H] and O3[H].
- ItemPirólise de resíduos da cultura de pimenta-do-reino capixaba: atividade experimental problematizada (AEP)(Universidade Federal do Espírito Santo, 2025-03-10) Welsing, Gyovana Lima; Machado, Marta Albuquerque; https://orcid.org/0000-0001-8335-3351; http://lattes.cnpq.br/5991893415892784; Moura, Paulo Rogério Garcez de; https://orcid.org/0000-0002-6893-3873; http://lattes.cnpq.br/9815585530252572; https://orcid.org/0009-0000-8824-3282; http://lattes.cnpq.br/5822936503097126; Dalmaschio, Cleocir José ; https://orcid.org/0000-0002-3773-5786; http://lattes.cnpq.br/5209978120430790; Silva, André Luis Silva da ; https://orcid.org/0000-0002-8245-9389; http://lattes.cnpq.br/0808253492421363This dissertation investigates the use of black pepper crop residues as promising lignocellulosic biomass, focusing on its physicochemical characteristics, energy potential and didactic application in the teaching of Chemistry. The biomass had a majority composition of carbon and oxygen (above 90%), in addition to 9.38% moisture, 79.43% volatiles, 11.18% ash and 9.39% fixed carbon. Pyrolysis was performed for bio-oil production, and the best yield (51.53%) was obtained at 550 °C, with a heating rate of 20 °C min⁻¹ and an N₂ flow of 100 mL min⁻¹. The bio-oils were chemically characterized, identifying compounds such as carboxylic acids, ketones and hydrocarbons, with potential energy and biotechnological application. The kinetic study, based on the Flynn–Ozawa–Wall, Kissinger–Akahira–Sunose and Friedman isoconversion models, indicated mean activation energies between 161–163 kJ mol⁻¹ and high thermal dependence; The use of catalyst did not significantly alter the kinetic patterns. In the field of teaching, the didactic intervention revealed advances in the understanding of the concepts of Chemical Kinetics, especially in the quantitative aspects. Indicators of metacognitive development showed gains in analytical (5.38–5.76), practical (4.68–5.28), and creative (5.06–5.53) capacities. The Grounded Theory revealed that factors such as the contextualization in sustainability, the availability of basic equipment and student engagement were determinant for the success of the proposal, although challenges such as lack of advanced equipment and reduced time for deepening were identified. The results show the potential of integration between science and education, promoting connections between academic knowledge and socio-environmental issues, and contributing to the training of critical professionals committed to sustainability