Mestrado em Química

URI Permanente para esta coleção

http://repositorio.ufes.br/handle/10/17502

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

Navegar

Agora exibindo 1 - 5 de 279

Membranas de acetato de celulose derivadas de biomassa e modificadas com TiO2/óxido de grafeno para tratamento de emulsões de petróleo em água
(Universidade Federal do Espírito Santo, 2024-07-26) Schmidt, Djanyna Voegel de Carvalho; Dalmaschio, Cleocir; https://orcid.org/0000-0002-3773-5786; Freitas, Jair Carlos Checon de; https://orcid.org/0000-0002-4474-2474; Machado, Marta Albuquerque; Cerqueira, Daniel Alves
Considering the environmental impact and health risks caused by oily wastewater in the petrochemical industry, it is crucial to develop more efficient separation techniques than traditional methods, such as membrane separation, for treating stable emulsions enriched with natural surfactants. This study investigated the preparation of dense cellulose acetate membranes from a low-cost biomass precursor (Luffa cylindrica) and their modification with graphene oxide and TiO2 nanoparticles, aiming to obtain a polymeric nanocomposite with good flow characteristics and selectivity for the treatment of oil/water emulsions. The obtained materials were characterized using techniques such as X-ray diffraction, nuclear magnetic resonance spectroscopy, and infrared absorption spectroscopy, along with optical and scanning electron microscopy, among others. The results revealed cellulose with a crystallinity index of 83%, cellulose triacetate with a degree of acetylation of 2.64 and a molar mass of 38,722 g/mol, as well as graphene oxide with a high degree of oxidation and graphene oxide modified with TiO2 in its anatase form. The membranes were prepared using the phase inversion technique and modified with the mentioned nanostructured materials. Microscopy analyses revealed that the membranes with the addition of graphene oxide functionalized with TiO2 showed better interaction with the cellulose acetate matrix. The flow and rejection analyses with oil emulsion revealed that the cellulose acetate membrane exhibited 63% oil rejection but faced fouling issues. Membranes modified with graphene oxide improved flow, but selectivity was compromised due to lower compatibility of the material with the cellulose acetate matrix. Membranes modified with graphene oxide and TiO2 nanoparticles showed significant improvements in fouling resistance compared to unmodified membranes and those modified with graphene oxide. These enhanced properties highlight the potential of modified cellulose acetate membranes for application in industrial wastewater treatment.
Utilização de solventes eutéticos profundos em resinas poliméricas quimicamente recicladas para determinação multielementar
(Universidade Federal do Espírito Santo, 2024-10-09) Rasch, Matheus Barbosa; Lima, Maria Tereza Weitzel Dias Carneiro ; https://orcid.org/0000-0002-8731-5093; http://lattes.cnpq.br/; Silva Filho, Eloi Alves da ; https://orcid.org/0000-0002-9306-7882; http://lattes.cnpq.br/; https://orcid.org/0009-0002-4069-6180; http://lattes.cnpq.br/; Souza, Jefferson Rodrigues; https://orcid.org/; http://lattes.cnpq.br/; Dalmaschio, Cleocir José; https://orcid.org/; http://lattes.cnpq.br/
The search for greener methodologies has challenged analytical chemists, leading to the development of methods that minimize environmental impact and risks to analysts. Green Analytical Chemistry, composed of 12 principles, has been a guide for these innovations, with recent emphasis on deep eutectic solvents (DES). These mixtures formed by intermolecular interactions provide unique physicochemical properties, such as melting point, viscosity, density and solubility, making them attractive for extractions and solubilizations. Among DES, natural deep eutectic solvents (NADES), composed of substances of primary metabolic origin, are even more sustainable, being formed by compounds with low toxic potential. Despite their advantages, DES are still rarely applied to certain samples, such as polymers, which have been the focus of growing concern due to the presence of microplastics and contamination by trace elements. Given this scenario, this study aims to determine trace elements (Al, Ba, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Sb, Ti and Zn) in chemically recycled polymeric resin, developed in partnership between UFES and Vale, using DES as a greener alternative to conventional methods. Four DES were prepared based on choline chloride and water, combined with malic acid, oxalic acid, phenol and urea, of which three are NADES. The polymeric samples were subjected to ultrasound-assisted extraction (UAE-DES) and analyzed by ICP-MS. The characterization of the DES by FTIR and NMR confirmed their adequate formation, and the Hansen solubility parameters (HSP) were used to understand the solvent-sample interactions - wich allowed the unprecedented determination of the sample’s Hansen solubility parameters itself. The results showed that DES were effective in recovering elements such as antimony (Sb), barium (Ba), and manganese (Mn), although the recovery efficiency varied: Sb was determined in all DES, Ba in NADES, and Mn only in solvents formed with acids. The AGREEprep metric demonstrated the environmental advantage of DES over the traditional microwave-assisted acid decomposition (MW-AD) method, with the highest score of 0.61 for NADES. However, elements such as aluminum (Al) and iron (Fe) showed unsatisfactory recoveries, suggesting the need for method optimization. The use of DES is a viable alternative for the preparation of recycled polymeric samples, with promising results for multielement determination and considerable environmental advantages. Additional adjustments may improve the recoveries of some elements and expand the use of the methodology to other matrices
Reciclagem do cátodo de bateria de íons de lítio do tipo LiFePO4 (LFP) e aplicação do material reciclado como pseudocapacitor
(Universidade Federal do Espírito Santo, 2024-07-30) Querubino, Renan Bobbio; Freitas, Marcos Benedito José Geraldo de; https://orcid.org/0000-0003-1521-774X; Machado, Marta Albuquerque; Pietre, Mendelssolm Kister de
Recycling lithium-ion batteries (LIBs) is an effective method of solid waste treatment and is crucial for the recovery of scarce, high-value metals that are of great technological importance. In this work, spent LIBs from electric vehicles were recycled through hydrometallurgical and pyrometallurgical processes, utilizing both citric acid and hydrogen peroxide leaching and alkaline leaching. The exhausted cathode material was characterized using X-ray Diffraction (XRD), Raman Spectroscopy, Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), identifying LiFePO4, Fe2O3, and FePO4 as the primary phases in its composition, along with the secondary phases Fe(OH)3 and Fe2(PO4)O. The hydrometallurgical recycling process, performed by acidic leaching of the cathode with 1.0 mol L−1 citric acid and hydrogen peroxide, showed low selectivity for the leaching of lithium and iron. In contrast, alkaline leaching proved to be more effective in recovering lithium and preserving the structural components of the material, such as LiFePO4, while not leaching iron, resulting in a more efficient separation of battery constituents. From the residue of alkaline leaching, lithium ferrite (β-LiFe5O8) was synthesized. Structural and morphological characterizations of lithium ferrite, performed by XRD, Raman Spectroscopy, and SEM, indicated the formation of a disordered crystalline phase with agglomerated grain morphology, with particles of undefined size. The electrochemical evaluation of the recycled material as a pseudocapacitor was promising. The recycled material exhibited a pseudocapacitive profile with a maximum specific capacitance of 7.6 F g−1 and capacitance retention of 82% over 250 cycles, at a charge-discharge current density of 0.7 A g−1. The pseudocapacitive profile of this material included contributions from electric double-layer charge storage and Faradaic processes. This study demonstrates the feasibility of recycling spent lithium-ion battery materials, transforming them into high-value-added materials with promising technological applications, contributing to sustainability and the circular economy.
Busca de plantas medicinais da Renisus através da triagem virtual para atividade anti-Helicobacter pylori
(Universidade Federal do Espírito Santo, 2024-04-26) Mendes, Campili; Kitagawa, Rodrigo Rezende ; https://orcid.org/; http://lattes.cnpq.br/; https://orcid.org/; http://lattes.cnpq.br/; Beltrame, Flávio Luís ; https://orcid.org/; http://lattes.cnpq.br/; Borges, Warley de Souza ; https://orcid.org/; http://lattes.cnpq.br/
Helicobacter pylori (H. pylori) is a Gram-negative bacterium that infects and colonizes the gastric mucosa of around half of the world's population, and its prevalence is higher in developing countries, reaching up to 90%. H. pylori infection triggers a series of diseases ranging from gastritis and ulcers to gastric cancer, which is the fifth most common cancer in humans. The bacterium is considered a group I carcinogen, according to the World Health Organization, and is included in the list of high-priority bacteria in the development of new drugs. In this context, medicinal plants and their phytocompounds are valuable shortcuts for discovering new, safer antibiotics with reduced adverse effects. In this context, the aim of this study was to select species from the National List of Medicinal Plants of Interest to the Unified Health System (Renisus) with potential anti-H. pylori activity, firstly through a bibliographic survey, followed by the creation of a phytochemical database and evaluation in an activity prediction model using PASS (Prediction of Activity Spectra for Substances), Tanimoto Similarity and, finally, in vitro evaluation. Once the species had been selected, the chemical profile was determined by high-resolution mass spectrometry (ESI-FT-ICR/MS - Electrospray Ionization-Fourier Transform Ion Cyclotron Resonance/Mass spectrometry) and liquid chromatography coupled to mass spectrometry (LC-MS - Liquid chromatography-mass spectrometry), and the compounds identified were analyzed by molecular docking in the active site of the bacterial target. After the bibliographic survey, 4 species were selected based on studies against gastritis and ulcers, but without studies against H. pylori, namely: Bauhinia forficata, Jatropha gossypiifolia, Sonalum paniculatum and Vernonia condensata. In the virtual screening, using PASS, the species J. gossypiifolia showed more compounds with the possibility of being active for 02 targets of action: the enzymes urease and fumarate reductase. Tanimoto's similarity analysis used standard inhibitors of these targets, acetohydroxamic acid and licochalcone A, respectively, to which the compounds present in J. gossypiifolia showed better similarity compared to the other species. To validate the virtual screening, in vitro tests were carried out to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extracts of the 4 selected species, with J. gossypiifolia showing the best results with a MIC of 64 µg/mL and MBC of 128 µg/mL. An in vitro urease inhibition test was also carried out, but none of the species selected showed satisfactory concentration/response activity against the enzyme. Among the compounds suggested by ESI-FT-ICR/MS and LC-MS, C-glucosilated flavonoids such as 3-genistein-8-C-glycoside and derivatives of luteolin and apigenin had the potential to interact with the active site of furamate reductase, hydrogen bonding with Arg404. In addition, 3-genistein-8-C-glucoside and luteolin 7-O-glucoside have five hydrogen bonds with amino acid residues, which is similar to the interaction of the fumaric acid ligand in the enzyme's active site. In view of the above, virtual screening proved to be a valuable tool in this study, and J. gossypiifolia showed promising activity and could represent an alternative source of compounds for treating H. pylori and preventing its harmful effects
Desenvolvimento de eletrocatalisadores a base de óxidos de Sn, Co e Cu para a eletrorredução de CO2
(Universidade Federal do Espírito Santo, 2024-03-04) Garcia, Robson Roella; Ribeiro, Josimar ; https://orcid.org/0000-0002-9544-1647; http://lattes.cnpq.br/1265145498501171; https://orcid.org/0009-0002-2674-6612; http://lattes.cnpq.br/8820348835691850; Ferreira, Rafael de Queiroz ; https://orcid.org/0000-0002-5190-8508; http://lattes.cnpq.br/5053247764430323; Rosa, Thalles Ramon ; https://orcid.org/0000-0001-9913-5885; http://lattes.cnpq.br/2629035369494897
The electrochemical reduction of CO2 (RECO2) using electrocatalysts could be an alternative to overcome the problems generated by high CO2 emission rates. To catalyze RECO2 in the formation of other products, there are several metal oxides described in the literature, such as SnO2, Co3O4 and CuO. SnO2, Co3O4 are able to catalyze RECO2 to formate, CuO to reduce CO2 to methane, formate, ethanol and carbon monoxide. The aim of this work was to synthesize electrocatalysts based on pure Sn, Co and Cu oxides supported on Vulcan XC 72 carbon by the simple ion coprecipitation method. In order to characterize the crystal structures of the synthesized materials, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and Raman techniques were used. Initially, the XRD data confirmed the formation of the synthesized oxides. However, the carbon-supported materials did not show any characteristic peaks using this technique, probably due to their amorphous structure. The Raman technique made it possible to identify carbon in the samples supported on Vulcan XC 72 carbon. SEM and MET data made it possible to identify the morphology of the particles. Thus, it was possible to observe the formation of spherical agglomerates with an average size of 11.0 nm for SnO2 and 13.0 nm for SnO2/C. In the case of Co3O4, Co3O4/C, polygonal particles with an octahedral shape were formed with an average size of 15.7 nm for Co3O4 and 20.6 nm for Co3O4/C. For CuO and CuO/C, agglomerates of particles with an average size of 30.0 nm and 40.0 nm were formed. The electrocatalysts were characterized using the cyclic voltammetry (CV) technique. The oxidation and reduction peaks of the oxides were observed at −1.5 V to 1 V (versus Ag/AgCl (KCl 3.0 mol L−1)). Linear scanning voltammetry (LSV) was then used to study the electrochemical behavior of the oxides synthesized in the presence of CO2. VVL showed that the Co and Cu materials presented a higher current in an N2-saturated medium than in a CO2-saturated solution, indicating that there was competition in the hydrogen evolution reactin was favored. Among the materials studied, CuO/C was the electrocatalyst that showed the best current density when saturated with CO2, at a potential of −1.6 V (versus Ag/AgCl (KCl 3.0 mol L−1)). This material was then used in RECO2 using the chronoamperometry technique, applying a fixed potential of −1.6 V (versus Ag/AgCl (KCl 3.0 mol L−1)) for 30 min, in a solution with a constant flow of CO2. Finally, aliquots of this solution were removed and analyzed via nuclear magnetic resonance, which indicated the formation of some products from the reduction of CO2 such as ethane, acetone and acetate. These studies have therefore demonstrated the potential use of electrocatalysts synthesized by simple ion coprecipitation for the electrochemical reduction of CO2

Navegar

Submissões Recentes