Química

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http://repositorio.ufes.br/handle/10/17500

Programa de Pós-Graduação em Química

Centro: CCE
Telefone: (27) 4009 2909
URL do programa: http://www.quimica.vitoria.ufes.br

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Agora exibindo 1 - 7 de 7

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
Membranas de poliamida 11 por inversão de fase: um estudo de miscibilidade, morfologia e estrutura
(Universidade Federal do Espírito Santo, 2020-02-18) 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; Dalmaschio, Cleocir Jose; https://orcid.org/0000000237735786; http://lattes.cnpq.br/5209978120430790; Almeida, Luiz Carlos Pimentel; https://orcid.org/; http://lattes.cnpq.br/0064380963494664
Polyamide 11 (PA11) membranes are prepared by phase inversion (PI) methodology using formic acid (FA) as solvent. The membranes morphology was investigated by Scanning Electronic Microscopy (SEM) analysis. The polyamide film showed a dense and homogenous structure, on the contrary the composition of 15% (w/w) polymer membrane showed macrovoids. In the other hand, de 20 and 25% (w/w) polymer membranes showed sponge like pores structures from a thermodynamic domain. These membranes have medium pores diameters between 0-10 µm calculated by image analysis. The X-Ray Diffraction (XRD) analysis show peaks at 2θ ~ 22° characteristic of γ crystalline form for 15% (w/w) polymer membrane and predominant peak 2θ~21° attributed to α form in 20% and 25% (w/w) membranes. The convection of phase γ to α occurred in function of increase of polymer concentration in membranes and this phenomenon was observed by an additional exothermic peak in Differential Scanning Calorimetry (DSC) curves. The degree of crystallinity was 8.2%, 10.9% and 11,3% for membranes with 15%, 20% and 25% (w/w), respectively. FTIR analysis showed characteristic bands of polyamide 11 for the membrane spectrum. Corresponding in the spectrogram that more intense bands were founded in the 719 cm-1 region indicating the presence of the γ phase. Moreover, the C=O stretch (amide I) and –NH-CO- vibration group (amide II) was observed in theoretical and experimental results. The stress-strain analysis of membranes shows a proportional dependence of Young’s modulus with the increase of polymer concentration in each membrane. The observed values of Young’s Module are 2.8, 3.2 and 3.5 MPa for 15, 20 and 25% (w/w), respectively. Cellulose fibers reinforced the rigidity of the membranes, decreasing the ductility and the variation or elastic module. Was observed the presence of cellulose fibers in all membranes, since the polymeric matrix behaves like the matrix of membranes without adding cellulose reinforcement. Thus evidencing that there was no influenced of the cellulose fiber on the thermodynamic parameters of the ternary system PA11/AF/H2O during the process of reorganization of the polymeric chain in the coagulation bath
Óxidos Mistos (ZnO/Fe2O3/ZnFe2O4@SiO2) Reciclados a Partir de Baterias de Zn-MnO2 e Rejeitos de Mineração de Ferro Aplicados como Fotocatalisadores, Pseudocapacitores e Sensores Eletroquímicos
(Universidade Federal do Espírito Santo, 2024-02-02) Magnago, Luma Barbosa; Lelis, Maria de Fátima Fontes; https://orcid.org/0000-0002-4828-4482; http://lattes.cnpq.br/9047743898158654; Freitas, Marcos Benedito José Geraldo de; https://orcid.org/0000-0003-1521-774X; http://lattes.cnpq.br/3485939623614913; https://orcid.org/0000-0002-5271-5572; http://lattes.cnpq.br/4135641802415178; Garcia, Eric Marsalha; https://orcid.org/0000-0002-3731-7568; http://lattes.cnpq.br/8006969980460016; Almeida, Luiz Carlos Pimentel; https://orcid.org/; http://lattes.cnpq.br/0064380963494664; Morais, Verônica Santos de; https://orcid.org/0000-0002-7324-2057; http://lattes.cnpq.br/3680926664416715; Ferreira, Sandra Aparecida Duarte; https://orcid.org/0000-0002-4828-4482; http://lattes.cnpq.br/5439516820869374
In this study, mixed oxides were prepared using spent alkaline battery anodes, silt fraction (FS), and raw iron mining reject (RB), and applied as photocatalysts, pseudocapacitors, and electrochemical sensors. Characterization analyses revealed that the mixed oxides (FS) and (RB) are composed of SiO2, ZnO, Fe2O3, ZnFe2O4, and are formed by agglomerates of nanoscale particles with a diameter < 200 nm and cubic shapes. For the photocatalytic study, a complete 23 factorial design was conducted to determine the optimal conditions of pH, H2O2 quantity, and the mass of mixed oxide (FS) or (RB) required for the decolorization of 1.56 x 10-6 mol of methylene blue dye (AM) under solar irradiation. The maximum decolorization efficiency was 96 % after 30 min using mixed oxide (FS) and 90 % after 45 min using mixed oxide (RB) with 2.35 x 10-5 mol of H2O2 and 20 mg of the material at pH 3. The efficiencies remained unchanged even after four successive decolorization cycles, and no solution after treatment showed toxicity in the Allium cepa (onion seed) test. In electrochemical studies, mixed oxide (FS) exhibited favorable characteristics for pseudocapacitor application due to its high capacitance (87.16 F g -1 ), energy density (27.24 Wh kg-1 ), power density (524.41 W kg -1 ), and reversibility (93 %). On the other hand, mixed oxide (RB) showed better sensitivity for use as an ascorbic acid (AA) sensor, with a value of 0.23 A mol-1 L cm-2 . This study encompasses recycling of waste and rejects to prepare new materials with multifunctional applications, contributing to environmental sustainability, preservation of raw materials, and the generation of a circular economy.
Reciclagem do eletrodo positivo de baterias de íon-Li exauridas utilizando ácido cítrico como lixiviador e precursor na formação de eletroquímica de Co(OH)2/Co3O4/LiCoO2 e química de Co3O4/LiCoO2
(Universidade Federal do Espírito Santo, 2016-03-31) Santana, Ívina Langsdorff; Freitas, Marcos Benedito José Geraldo de; Lelis, Maria de Fátima Fontes; Ferreira, Rafael Queiroz; Almeida, Luiz Carlos Pimentel
In this present work, cobalt and lithium from spent lithium ion batteries Samsumg® and HP® was recovered in hydrometallurgical process. Citric acid was leachant and H2O2was reductant agent. Two recycling routes was developed using leaching solution of cobalt and lithium: an electrochemical route; and a synthetic route. On electrochemical route, cobalt oxides (LiCoO2and Co3O4) and hydroxides electrodeposited on nickel substrate using galvanostatic technique. High current density of -0,45 Acm-2used for electrodeposition due to great stability of cobalt and lithium complex. Electrodeposition carried out using charge densities of -250, -300 and -350Ccm-2. Electrochemical recycling route presented low efficiency of electrodeposition (~1,5%) and recycled material, tested as pseudocapacitors, presented irrelevant capacitances (lower than 1 Fg-1). Synthetic recycling route was carried out using a sol-gel method for LiCoO2and Co3O4preparation. To form sol-gel precursor, leaching solution of cobalt and lithium citrate was used. Sol-gel precursor calcined at 250°C, 350 °C, 450 °C and 650 °C formed a mixed cobalt oxides compounds (LiCoO2and Co3O4). Mixed cobalt and lithium oxides tested as catalyst for methylene blue photodegradation presented good catalytic activity. Mixed cobalt oxides calcined at 450 °C degraded 90% of methylene blue after 10 hours and 100% after 24 hours of photocatalysis. Sol-gel precursor calcined at 850 °C formed only LiCoO2. Electrochemical properties of recycled cobalt and lithium oxide were studied using cyclic voltammetry. Recycled LiCoO2is a promising material for lithium ion batteries cathodes. The contribution of this work is that it presents a means to produce valuable materials having electrochemical and catalytic properties from recycled batteries trough a spent lithium ion batteries without polluting the environment
Síntese de NiFe2O4 a partir do níquel reciclado de baterias Ni-MH e suas aplicações multifuncionais como um catalisador em processos foto Fenton e como um pseudocapacitor eletroquímico
(Universidade Federal do Espírito Santo, 2018-03-16) Magnago, Luma Barbosa; Lelis, Maria de Fátima Fontes; Freitas, Marcos Benedito José Geraldo de; Athayde, Geisamanda Pedrini Brandão; Almeida, Luiz Carlos Pimentel
In this study, a co-precipitation method was used for the synthesis of undoped ferrites (Fe2O3/Fe3O4-R) and nickel-doped ferrites from nickel reagents (NiFe2O4-R) and from nickel recycled from spent nickel–metal hydride (Ni-MH) batteries (NiFe2O4-B). Ferrite structure and composition were confirmed by X-ray diffraction (XRD), energy dispersive X-ray (EDX) and inductively coupled plasma optical emission spectrometry(ICP-OES). Scanning electron microscopy (SEM) showed agglomerated particles of different sizes and shapes and the transmission electron microscopy (TEM) revealed spherical particles of 50 nm. Ferrites are a multifunctional material that can be used as a catalyst and pseudocapacitor. The catalytic properties of ferrites were analyzed by measuring the decolorization of methylene blue (MB) in a photo-Fenton process under solar radiation. The experimental design ranked ferrites in the following order of MB decolorization efficiency: NiFe2O4-B = NiFe2O4-R > Fe2O3/Fe3O4-R. Using NiFe2O4-B, MB solutions were decolorizedwith more than 90% efficiency in 90 min. ICP-OES analyzes of the solution contained indetected concentrations of (0.00057 ± 0.00067) mg L-1of nickel ions and undetected concentration of ironions. The concentrations of nickel and iron ions arelower than the standard effluent release concentrations indicated CONAMA resolution 430/2011. NiFe2O4-B ferritedoes not transfer metals ions present in its composition to the solution. Analysis of the MB solution by ion chromatography after the NiFe2O4-B-catalyzed decolorization showed the presence of formic, acetic, and propionic acids.Pseudocapacitive properties, analyzed by cyclic voltammetry, showed that NiFe2O4-B have higher charge efficiency (84.3%) when compared with NiFe2O4-R (65.5%) and Fe2O3/Fe3O4-R (57%) after 1000 cycles. Ferrite NiFe2O4-B is an efficient catalyst for MB degradation andas pseudocapacitor
Síntese e caracterização de ferritas não dopadas e dopadas com Mn a partir de baterias Zn-MnO2 exauridas e suas aplicações catalíticas
(Universidade Federal do Espírito Santo, 2017-03-28) Barrada, Renan Vicente; Lelis, Maria de Fátima Fontes; Freitas, Marcos Benedito José Geraldo de; Silva Filho, Eloi Alves da; Almeida, Luiz Carlos Pimentel
In this current research, non-doped ferrites (Fe2O3/Fe3O4) and ferrites doped with manganese (MnFe2O4(R)) were synthesized using commercial reagents (MnFe2O4(B)) and manganese recovered from spend Zn-MnO2 batteries. The cathode of spend Zn-MnO2 batteries consists mainly of MnO2 and Mn3O4 according to X-ray diffraction (XRD) analysis. Analysis by inductively coupled plasma optical emission spectrometry (ICP OES) detected the presence of zinc from the anode of the batteries. The cathode manganese was leached with 0.5 molL-1 nitric acid and used as a dopant in the synthesis of MnFe2O4(B) ferrites. The synthesized materials presented characteristics of MnFe2O4, according to X-ray diffraction (XRD). The ferrites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the micrographs it was verified that the materials presented particles and agglomerates with varied and irregular geometry in nanoscale. By X-ray dispersive energy (EDS) spectrometry analysis coupled to the SEM, the composition of the synthesized ferrite particles could be analyzed. It obtained the peaks of Fe and O in the sample of Fe2O3/Fe3O4, and Fe, Mn and O in the samples of MnFe2O4(R) and MnFe2O4(B). The chemical composition of ferrites was determined by dichromatometry for iron and flame atomic absorption spectrometry (F AAS) for manganese and obtaine that 66.6% of Fe to Fe2O3/Fe3O4, 56.6% of Fe and 11.5% Mn for MnFe2O4(R), and 61.5% Fe and 4.5% Mn for MnFe2O4(B). The ferrites were catalytically evaluated in the discoloration of the methylene blue dye through the heterogeneous photo Fenton process, obtaining 15.6%, 98% and 92% of dye discoloration using Fe2O3/Fe3O4, MnFe2O4(R) and MnFe2O4(B) respectively, in 120 minutes of reaction.
Uso da RMN no estudo da despolimerização de poliuretano rígido
(Universidade Federal do Espírito Santo, 2019-03-26) Maioli, Juliana Proliciano; SILVA FILHO, Eloi Alves da; Cunha Neto, Álvaro; Freitas, Marcos Benedito José Geraldo de; Almeida, Luiz Carlos Pimentel
Polyurethanes (PUs) have been widely used in several trade sections. Thereby, large amounts of waste are produced and need to be correctly disposed off. Research on this theme has been helping industries to apply recycling processes that are cheap and efficient. In this work, the glycolysis of a rigid PU was performed using different catalysts. The catalysts used was: a tensoactive (CTAB), the NaOH, two ionics liquids (1-butyl-3-methylimidazole trichloromanganate and 1-butyl-3-methylimidazole trichlorozincate), and four Niobium salts (niobium pentoxide, niobium oxidehydrated, niobium pentachloride and niobium ammoniacal oxalate). 1H NMR technique was used to obtain the rate of PU depolymerization. Also was used the technique diffusion ordered spectroscopy 1H NMR (DOSY-NMR) that assisted in the identification composition of the mixture of products. In the glycolysis, glycerol (GCL) and diethylene glycol (DEG) were tested as glycolysis agents. The PU was synthesized to be free of additives in the depolymerization process, and its characterization was performed using infrared spectroscopy (FTIR) and 1H NMR spectroscopy analyses. The conversion rate provides information about which catalyst has the better catalytic activity. The use of NaOH as a catalyst presented conversion rate of 100 % in 30 min of reaction, as is already known in the literature, and the DOSY-NMR spectrum provided information about products that didn’t perceptible only by 1H NMR spectrum. Ionic liquids (LIs) as catalysts, presented conversion near of 80 % in 1h of reaction, which can be improved by modifying the reaction conditions. To determine the composition of the mixture of products in the depolymerization reaction, diffusion ordered spectroscopy 1H NMR (DOSY-NMR) was used. The Niobium salts had non-catalytic behavior, because they showed conversion rate lower than uncatalyzed reaction. DOSY-NMR indicated a complex mixture of reaction by-products, differently from the 1H NMR data, which indicated the formation of a simple diamine-terminated by-product.

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