Doutorado em Química

URI Permanente para esta coleção

http://repositorio.ufes.br/handle/10/17501

Nível: início
Ano de início: 2014
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=956/a>

Navegar

Submissões Recentes

Agora exibindo 1 - 5 de 86
  • Nenhuma Miniatura disponível
    Item
    Estudo da miscibilidade de blendas poliméricas : influência na morfologia e eficiência de membranas
    (Universidade Federal do Espírito Santo, 2024-12-03) Lima, Rayanne Penha Wandenkolken; Silva Filho, Eloi Alves da ; https://orcid.org/0000-0002-9306-7882; http://lattes.cnpq.br/8259708288584235; https://orcid.org/0000-0001-8558-302X; http://lattes.cnpq.br/2557592261324003; Almeida, Luiz Carlos Pimentel; http://lattes.cnpq.br/0064380963494664; Prado, Adilson Ribeiro ; https://orcid.org/0000-0001-8808-4488; http://lattes.cnpq.br/3085491325255749; Dalmaschio, Cleocir José ; https://orcid.org/0000-0002-3773-5786; http://lattes.cnpq.br/5209978120430790; Machado, Marta Albuquerque ; https://orcid.org/0000-0001-8335-3351; http://lattes.cnpq.br/5991893415892784
    Sustainability, understood as social and environmental responsibility, is a fundamental principle for mitigating the environmental challenges associated with the production and disposal of plastics. In this context, the present work aims to correlate the morphology of membranes obtained via Non-Solvent Induced Phase Separation (NIPS) from polymer blends with the miscibility analysis of the blends themselves. Two blends were prepared for this purpose: the first composed of two semi-crystalline polymers, one of recycled origin and the other of green origin; and the second composed of one semi-crystalline polymer and one amorphous polymer, both recycled. The miscibility of the blends was evaluated using DSC and confirmed through dynamic mechanical analysis (DMA). The first blend demonstrated partial immiscibility, with a reduction in the equilibrium melting temperature (Tºm) and showed three glass transition peaks (Tg), indicating separate phases. The Flory-Huggins interaction parameter (χ12) for this blend was positive (1.115 × 10⁻⁴), indicating a barrier to total miscibility. The resulting membranes presented a dense, spongy and homogeneous morphology, with macrovoid formation. Permeability and porosity analyses indicated potential for nanofiltration or reverse osmosis applications. Meanwhile, the second blend exhibited two Tg peaks, suggesting miscibility relative to its composition, with a negative χ12 (-2.057 × 10⁻⁴), indicating favorable interactions, though insufficient for complete miscibility. Morphological analysis of these membranes revealed the presence of macrovoids associated with partial immiscibility and thermodynamic instability, resulting in lower selectivity and mechanical resistance. These characteristics classify them for ultrafiltration-type applications
  • Nenhuma Miniatura disponível
    Item
    Nanoemulsão estabilizada com quitosana modificada e nanocelulose aplicadas na recuperação avançada de petróleo
    (Universidade Federal do Espírito Santo, 2025-04-01) Pinto, Roberta Tristão; Nascimento, Andreas; https://orcid.org/0000-0002-4465-5450; http://lattes.cnpq.br/2072155247986639; Lacerda Júnior, Valdemar; https://orcid.org/0000-0002-8257-5443; http://lattes.cnpq.br/9819471276433138; https://orcid.org/0000-0002-7031-9813; http://lattes.cnpq.br/4067639048997633; Cunha Neto, Álvaro; https://orcid.org/0000-0002-1814-6214; http://lattes.cnpq.br/7448379486432052; Queiroz, Vagner Tebaldi de; https://orcid.org/0000-0002-8170-125X; http://lattes.cnpq.br/9963384168622230; Santos, Luiz Carlos Lobato dos; https://orcid.org/0000-0003-3824-7802; http://lattes.cnpq.br/8891045064075199; Araújo, Lorraine Louise Greco Cavalcanti de; https://orcid.org/0000-0003-3824-7802; http://lattes.cnpq.br/8891045064075199
    In the current scenario of petroleum reserve depletion, chemical injection is a vital technique for enhanced oil recovery (EOR). This article presents an approach for developing an oil recovery fluid through experimental investigations and mechanistic descriptions of nanoemulsified systems. The nanoemulsions were stabilized by a cationic surfactant, cetyltrimethylammonium bromide (CTAB), an anionic amphiphilic polymer synthesized from chitosan (NaP-CMQ), and cellulose nanoparticles (CNC) extracted from banana pseudostem. The utilized compounds underwent comprehensive characterization. The physicochemical properties of the nanoemulsions include surface tension, pH, conductivity, droplet size (DLS), zeta potential, rheological behavior, phase behavior, IFT, wettability, and miscibility with crude oil. DLS results confirmed the formation of nanometric oil droplets (<500 nm) in the nanoemulsion phase for all systems. Nanoemulsions stabilized with polymer and surfactant were more efficient in reducing IFT (1.88 mN/m), while nanoemulsions stabilized with polymer/surfactant and nanoparticles promoted greater wettability alteration (19°). Rheological experiments demonstrated pseudoplastic behavior of the nanoemulsions through the adjustment of flow parameters using the power-law model. Crude oil emulsification studies revealed favorable miscibility with crude oil at 70°C, with synergistic interactions between polymer, surfactant, and nanoparticle. The recovery factor was 48.1 % of the original oil in place (OOIP) for the nanoemulsion stabilized with NaP-CMQ+CTAB+CNC. In summary, the developed nanoemulsion-based systems exhibit promising physicochemical and stabilization characteristics for EOR applications
  • Nenhuma Miniatura disponível
    Item
    Solos e cafés: relações entre composição química, clima e qualidade
    (Universidade Federal do Espírito Santo, 2025-04-04) Frinhani, Roberta Quintino; Oliveira, Emanuele Catarina da Silva; https://orcid.org/0000-0003-0699-6104; http://lattes.cnpq.br/1715851915787164; Castro, Eustáquio Vinícius Ribeiro de; https://orcid.org/0000-0002-7888-8076; http://lattes.cnpq.br/1055263403980509; https://orcid.org/0000-0001-8713-4877; http://lattes.cnpq.br/7313374219256535; Dalmaschio, Cleocir José; https://orcid.org/0000-0002-3773-5786; http://lattes.cnpq.br/5209978120430790; Athayde, Geisamanda Pedrini Brandão; https://orcid.org/0000-0002-4315-0653; http://lattes.cnpq.br/8037324704189596; Rocha, Julia Tristão do Carmo; https://orcid.org/0000-0002-7484-0139; http://lattes.cnpq.br/6899104555589459; Berilli, Sávio da Silva; https://orcid.org/0000-0003-0554-8756; http://lattes.cnpq.br/1703547133505721
    Coffee quality results from the interaction between the chemical composition of beans and their sensory characteristics, influenced by factors such as climate, soil, and management. Understanding these factors is essential for establishing quality parameters and improving farming practices. This study aimed to chemically characterize soils and specialty coffee beans from Coffea arabica and C. canephora, from different Brazilian regions, using EDXRF, MIR, and NIR techniques with statistical modeling, to evaluate their contribution to beverage quality and the influence of environmental factors on composition. Data were integrated to assess the relationship between composition and beverage quality in C. arabica, while for C. canephora soils, the influence of environmental variables such as climate and geology was investigated. EDXRF identified Fe, Al, Ti, Zr, K, Ca, and Si as the main elements contributing to soil differentiation. In coffee beans, Ca, Mn, and Rb were prominent in green beans, whereas K, Ni, and Rb were more relevant in roasted beans. Tukey's tests revealed significant variations among sampling points, reflecting environmental and anthropogenic influences. In roasted coffees, a relative increase in elemental concentrations was observed due to mass loss during roasting, localized Ni presence possibly related to contamination, and reduction of volatile elements like sulfur. Pearson correlations showed positive associations between Al and Ga, and between Mg and K, and negative associations between Si and Al, Fe, and Ga. Regarding climate, precipitation was negatively correlated with Ga, Ag and Ca, and positively with Cu; temperature correlated negatively with Rb and Ca, while altitude had a positive correlation with Rb. Infrared spectral data allowed discrimination of soils and coffees based on chemical profiles, revealing bands of minerals (kaolinite, gibbsite, quartz), organic matter in the soil, and compounds like phenolics, caffeine, carbohydrates, and lipids in coffee. Roasting resulted in reductions in water, chlorogenic acids, caffeine, and carbohydrates compared to green beans, relative lipid preservation, and increased bands attributed to carbonyl compounds. Integration of chemical and sensory data did not reveal a direct relationship between soil composition and coffee quality. However, in green coffee, sulfur, Mn, Fe, chlorogenic acids, and lipid oxidation products showed negative correlations with beverage quality. In roasted coffee, sulfur, pyruvic and quinic acids, caffeine, pyridine, and fatty acids were also negatively correlated. Conversely, carbonyl compounds in green coffee, as well as aliphatic acids, esters, and lipids in roasted coffee, were positively associated with better sensory attributes. Results demonstrate that chemical characterization through spectroscopic techniques, combined with statistical modeling and data integration, enabled understanding of relationships between composition and beverage quality, especially in Coffea arabica. Furthermore, the influence of environmental factors on C. canephora soils was highlighted, reinforcing the potential of rapid, sustainable spectroscopic methods to support understanding of coffee quality and improve agricultural management.
  • Nenhuma Miniatura disponível
    Item
    Catalisadores heterogêneos suportados em materiais de carbono porosos partindo de rejeitos de uma rocha ornamental carbonática : preparação, caracterização e aplicação para obtenção de biodiesel
    (Universidade Federal do Espírito Santo, 2025-03-27) Aleixo, Fábio da Costa; Silveira, Leonardo Luiz Lyrio da; http://lattes.cnpq.br/5020611563370937; Freitas, Jair Carlos Checon de ; https://orcid.org/0000-0002-4474-2474; http://lattes.cnpq.br/3074997830683878; https://orcid.org/0000-0001-5554-5575; http://lattes.cnpq.br/5940065747018743; Labat, Gisele Aparecida Amaral ; https://orcid.org/0000-0003-3745-6119; http://lattes.cnpq.br/9764742132401600; Zagôto, Juliano Tessinari ; https://orcid.org/0000-0002-2878-4615; http://lattes.cnpq.br/8321874088120679; Machado, Marta Albuquerque ; https://orcid.org/0000-0001-8335-3351; http://lattes.cnpq.br/5991893415892784; Santos, Reginaldo Bezerra dos ; https://orcid.org/0000-0003-2966-7231; http://lattes.cnpq.br/6265396050660132
    The processing of carbonate rocks generates substantial amounts of waste, which are frequently mismanaged—either discarded into the environment or irregularly deposited in landfills—posing significant environmental concerns. This study explores the synthesis of heterogeneous catalysts supported on a carbonaceous matrix, using carbonate ornamental stone tailings (OST) as a low-cost source of calcium and magnesium oxides. Various chemicals routes were initially evaluated, with all materials subjected to thermal treatment at 800 °C for 3 hours under an inert atmosphere. Among them, the wet impregnation method involved mixing OST and coconut shell-activated carbon (CSAC) powders with a NaOH solution under constant stirring. In a subsequent step, the synthesis parameters for this method were optimized using a full factorial experimental design. The catalytic performance of the resulting materials was assessed in the transesterification of soybean oil with methanol for biodiesel production. Conversion efficiency was monitored and quantified by proton nuclear magnetic resonance spectroscopy in solution. Among the tested synthesis routes, wet impregnation yielded the highest conversion rates. In the optimization study, a maximum conversion of 85% was achieved using an OST/CSCA mass ratio of 50:20, followed by thermal treatment at 800 °C for 1 hour. Further optimization of the reaction conditions, performed via a central composite design, led to a maximum biodiesel yield of 91% under the following conditions: 5 wt% catalyst loading (relative to oil mass), 3 hours of reaction time, and a temperature of 60 °C. The catalysts demonstrated excellent activity, attributed to the formation of CaO, MgO, Na₂CO₃, and Na₂CO₃·CaCO₃ phases, as confirmed by X-ray diffraction, depending on the thermal treatment parameters. Analysis of the Ca and Mg content in the biodiesel revealed significantly reduced metal leaching when CACO was used as the support, with concentrations remaining below or only slightly above the 5.0 mg/kg threshold established by the European standard EN 14214. These findings confirm the feasibility of employing OST and coconut shells as sustainable feedstocks for the development of efficient, carbon-supported heterogeneous catalysts. The wet impregnation route emerged as the most effective strategy for depositing calcium and magnesium oxides onto the CSCA matrix, offering both economic and environmental advantages due to its reliance on waste-derived materials and minimal generation of secondary residues
  • Nenhuma Miniatura disponível
    Item
    Remoção do corante preto reativo 5 em solução aquosa por adsorção e/ou oxidação eletroquímica
    (Universidade Federal do Espírito Santo, 2025-02-27) Paquini, Lucas Destefani; Profeti, Demetrius ; https://orcid.org/0000-0003-4565-3331; http://lattes.cnpq.br/5030262115789096; Ribeiro, Josimar ; https://orcid.org/0000-0002-9544-1647; http://lattes.cnpq.br/1265145498501171; https://orcid.org/0000-0003-1285-8031; http://lattes.cnpq.br/3239593331960071; Lima, Fabio Henrique Barros de ; https://orcid.org/0000-0001-5501-2429; http://lattes.cnpq.br/8978509213666235; Costa, Carla Regina ; https://orcid.org/0000-0002-7057-6393; http://lattes.cnpq.br/0088443679133064; Cestarolli, Dane Tadeu ; https://orcid.org/0000-0003-1453-9499; http://lattes.cnpq.br/6247805873454988; Ferreira, Rafael de Queiroz ; https://orcid.org/0000-0002-5190-8508; http://lattes.cnpq.br/5053247764430323
    The expansion of the textile sector has played a fundamental role in accelerating industrialization on a global scale. However, this industry has caused significant environmental impacts, particularly due to the improper disposal of effluents with high contamination loads, including azo dyes, with reactive black 5 (RB-5) being one of the most concerning. Thus, the search for effective decontamination methods is essential, among which adsorption and electrochemical advanced oxidation processes stand out as promising strategies for the removal of these pollutants. This study investigated adsorption and electrochemical oxidation applied to RB-5 removal in synthetic effluents. In the adsorption process, a C/TiO2 composite was developed and characterized. X-ray diffraction (XRD) analysis indicated that both the composite and the TiO₂ support predominantly exhibited anatase phases. Scanning electron microscopy (SEM) revealed morphological changes in the material after adsorption. The specific surface area of the adsorbent was approximately 54.24 m2 g–1, while Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of various functional groups, some of which were related to the dye structure after adsorption. The point of zero charge (pHPZC) indicated favorable adsorption conditions for pH ≤ 7.47. After fitting to nonlinear equations, the Sips model best described the adsorption equilibrium. On the other hand, the adsorption kinetics followed the Avrami fractional order model, suggesting an adsorption governed by multiple stages. Thermodynamically, adsorption was classified as endothermic, entropy-controlled, and exergonic. The electrochemical oxidation process involved the development and characterization of dimensionally stable anode (DSA) with the Ti/IrO2-SnO2-Ta2O5 configuration. XRD analysis of the electrodes revealed characteristic phases of IrO2, SnO2, Ti, and Ta2O5, while SEM images displayed the typical "cracked mud" morphology. Cyclic voltammetry (H2SO4) evidenced the capacitive behavior of the electrodes, with a roughness factor ranging from 0.3260 to 0.6812. Electrochemical mass spectrometry (EC-MS) confirmed the predominance of electrogenerated molecular chlorine (Cl2) over the oxygen evolution reaction, especially under high Sn/Ta ratios and acidic pH conditions. Ion chromatography (IC) allowed the quantification of Cl⁻ and ClO⁻, while electrochemical impedance spectroscopy (EIS) evidenced that Cl₂/HOCl formation occurs at potentials above 1.25 V vs. Ag/AgCl, with lower charge transfer resistance (Rtc) in compositions containing up to 10% Ta. The chemical and structural stability of the electrodes was confirmed by the nearly constant solution resistance (Rs) and double-layer capacitance (Cdl), which indicated rough and porous surfaces. The RB-5 dye degradation process was efficient, with apparent rate constants ranging from 0.00121 to 0.00571 s–1, being most effective in the Ir/Sn/Ta 30:70:00, 30:65:05, and 30:60:10 electrodes. The chemical oxygen demand (COD) removal varied between 71.72% and 32.47%, and energy consumption was lower (0.482 kWh m–3) for compositions with lower Ta content. The results highlight the feasibility of both techniques (adsorption and electrochemical oxidation) for the treatment of industrial effluents containing dyes