Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
Navegar
15 resultados
Resultados da Pesquisa
Item Fotocatálise heterogênea com TiO2 para oxidação de arsênio e sua remoção de águas por coprecipitação com sulfato férrico(Química Nova, 2009) Mendes, Gisele; Bellato, Carlos Roberto; Marques Neto, José de OliveiraThe oxidation of arsenic (As(III) to As(V)) in water samples was performed by heterogeneous photocatalysis using a TiO2 film immobilized inside a photochemical reactor. After oxidation, As(V) was removed from the water samples by coprecipitation with ferric sulfate. The final conditions of oxidation and arsenic removal (TiO2 film prepared with a suspension: 10% (w/v); pH: 7.0; oxidation time: 30 min and Fe3+ concentration: 50 mg L-1) were applied in natural water samples which were supplemented with 1.0 mg L-1 of As(III) to verify the influence of the matrix. After treatment, more than 99% of arsenic was removed from the water.Item Borracha natural e nanocompósitos com argila(Química Nova, 2009) Rippel, Márcia Maria; Bragança, Fábio do CarmoThe natural rubber is a strategic material which can not be replaced by synthetic rubber in many technological applications. Brazil is a rubber importer, but new techniques of cultivation, breeding and diversification of producing species can reverse this situation. One of the best ways to add value to this commodity is nanotechnology. The production of nanocomposites is already a reality and shows that the sustainable use of this natural resource can lead to new products and boost the national agribusiness setting labor-qualified in the field.Item Síntese e avaliação da atividade fitotóxica de derivados da α-Santonina(Química Nova, 2009) Alvarenga, Elson S.; Barbosa, Luiz C. A.; Saliba, William A.; Arantes, Francisco F. P.; Demuner, Antônio J.; Silva, Antônio A.Mixtures of α-Santonin and various solvents were irradiated by either high or low pressure mercury lamps. The photochemical reactions afforded lumisantonin (11) (76% in acetonitrile), (3S,3aS,9bS)-3,6,6-trimethyl-3,3a,4,5-tetrahydronafto[1,2-b]furan-2,7(6H,9bH)dione (12) (100% in acetonitrile), 10α-acetoxy-3-oxo-1,7αH,6,11βH-guaia-4-en-6,12-olide (8) (26% in acetic acid), 10α-hydroxy-3-oxo-1,7αH,6,11βH-guaia-4-en-6,12-olide (10) (32%) and (E)-3-((3S,3aS,7aS)-3-methyl-2-oxo-6-(propan-2-ylidene)hexahydrobenzofuran-7-(7aH)-ylidene)propanoic acid (9) (44%) (in water/ acetic acid 1:1, v/v). Lactone 12 was also prepared by irradiation of lumisantonin in diethyl ether. Lactones 8 and 10 were converted, respectively, into the 10α-acetoxy-3β-hydroxy-1,7αH,6,11βH-guaia-4-en-6,12-olide (13) (87%) and 3β,10α-dihydroxy-1,7αH,6,11βH-guaia-4-en-6,12-olide (14) (75%) by sodium borohydride reduction. The effects of the compounds on the development of radicle of Sorghum bicolor and Cucumis sativus were evaluated.Item Mapping of quantitative trait loci for butter content and hardness in cocoa beans (Theobroma Cacao L.)(Plant Molecular Biology Reporter, 2009-06) Queiroz, Vagner T. de; Araújo, Ioná S.; Souza Filho, Gonçalo A. de; Pereira, Messias G.; Faleiro, Fábio G.; Guimarães, Cláudia T.; Moreira, Maurílio A.; Barros, Everaldo G. de; Machado, Regina C. R.; Pires, José L.; Schenell, Raymond; Lopes, Uilson V.Cocoa butter is an important raw material for the chocolate, pharmaceutical, and cosmetic industries. The butter content and quality in cocoa beans are genetically controlled characteristics, and affect its commercial value and industrial applicability. In the present work, an F2 population derived from the cross between the ICS-1 and Scavina-6 cocoa clones was used for molecular mapping. A linkage map was constructed based on amplified fragment length polymorphism, random amplified polymorphic DNA, and simple sequence repeat markers, resulting in a total of 273 markers, distributed in 14 linkage groups (LGs). Phenotyping of butter content was performed after ether extraction and butter hardness was determined by sweeping differential calorimetry. One quantitative trait locus (QTL) associated to butter content was mapped at linkage group 9 (LG9) and two QTLs for butter hardness were identified at linkage groups 9 and 7 (LG9 and LG7). The two QTLs mapped at the LG9 explained 51.0% and 28.8% of the phenotypic variation for butter content and hardness, respectively. These QTLs were concentrated in the same map region, suggesting a close genetic linkage or pleiotropic effect. The QTLs identified may be useful in further marker-assisted selection breeding programs aimed at cocoa butter quality improvement.Item Syntheses, crystal structure, spectroscopic characterization and antifungal activity of new N-R-sulfonyldithiocarbimate metal complexes(Journal of Inorganic Biochemistry, 2009-07) Alves, Leandro C.; Rubinger, Mayura M. M.; Lindemann, Renata H.; Perpétuo, Genivaldo Júlio; Janczak, Jan; Miranda, Liany D. L.; Zambolim, Laércio; Oliveira, Marcelo R. L.Five new compounds with the general formula of (Bu4N)2[M(RSO2NCS2)2], where Bu4N = tetrabutylammonium cation, (M = Ni, R = 4-FC6H4) (1), (M = Zn, R = 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 4-IC6H4), (2), (3), (4) and (5), respectively, were obtained by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO2NCS2K2) with nickel(II) chloride hexahydrate or zinc(II) acetate dihydrate in metanol:water 1:1. The elemental analyses and the IR data are consistent with the formation of the expected bis(dithiocarbimato)metal(II) complexes. The 1H and 13C NMR spectra showed the signals for the tetrabutylammonium cation and the dithiocarbimate moieties. The compounds 1, 2 and 5 were also characterized by X-ray diffraction techniques. The nickel(II) is coordinated by two N-4-fluorophenylsulphonyldithiocarbimato(2-) ligands forming a planar coordination. The zinc(II) exhibits distorted tetrahedral configuration in compounds 2 and 5 due to the chelation effect of two sulfur atoms of the N-R-sulfonyldithiocarbimate ligands. The antifungal activities of the compounds were tested in vitro against Colletotrichum gloeosporioides, an important fungus that causes the plant disease known as anthracnose in fruit trees. All the complexes were active.Item Applications of micelle and microemulsion systems containing aminated surfactants synthesized from ricinoleic acid as carbon-steel corrosion inhibitors(Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009-05-15) Gurgel, Alexandre; Moura, Everlane Ferreira; Wanderley Neto, Alcides de Oliveira; Dantas, Tereza Neuma de Castro; Scatena Júnior, HélioThe high affinity of surfactant molecules to adsorb onto interfaces is responsible for their applications in several interfacial systems. For this reason, surfactants can be used as good corrosion inhibitors in metallic surfaces. The main objective of this work was to examine the anticorrosion ability of three novel surfactant molecules synthesized from ricinoleic acid, a castor oil derivative. The surfactants are: sodium 12-N,N-diethylamino-9-octadecenoate (AR1S), sodium 12-N,N-diethylamino-9,10-dihydroxy-octadecanoate (AE2S) and sodium 12-N,N-diethylamino-9-octadecanoate (AE1S). Their ability to inhibit corrosion in AISI 1010 carbon-steel has been investigated by preparing specific micellar solutions and microemulsion systems. Adsorption phenomena have been electrochemically studied with the Frumkin model, indicating that the surfactant solutions tested can inhibit corrosion with levels as high as 95%. On the other hand, the microemulsion systems, although featuring relatively lower performance, are advantageous in that they are able to dissolve more active matter. These results are useful as a basis to propose and study particular applications such as the transport of oil in petrochemical industries.Item Separation of Cd and Ni from Ni–Cd batteries by an environmentally safe methodology employing aqueous two-phase systems(Journal of Power Sources, 2009-09-05) Lacerda, Vânia Gonçalves; Mageste, Aparecida Barbosa; Santos, Igor José Boggione; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol daThe separation of Cd and Ni from Ni–Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li2SO4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2 ± 3.1)% and Ni (10.6 ± 0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00 mmol kg−1, mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds.Item Contaminação por Cu e Cr na sub-bacia do Rio Pomba, em Minas Gerais(Revista Ceres, 2009-04) Carvalho, Juliana Vanir de Souza; Moreira, Eduardo Guimarães Araújo; Mendonça, Eduardo de Sá; Fontes, Maurício Paulo Ferreira; Fernandes, Raphael Bragança AlvesOs metais pesados são poluentes devido a suas diferentes espécies químicas, toxidades e propriedades acumulativas. Em ambientes aquáticos, os sedimentos têm sido usados na avaliação da contaminação por metais, uma vez que atuam como compartimento concentrador. A sub-bacia do Rio Pomba, localizada na Zona da Mata mineira, abrange diversas cidades, entre elas Cataguases, que se destaca por ser importante pólo industrial. O objetivo desta pesquisa foi avaliar a contaminação da água, do solo e do sedimento por Cu e Cr na sub-bacia do Rio Pomba, no trecho de Mercês à jusante de Cataguases. As amostras foram coletadas em seis pontos ao longo da sub-bacia, sendo determinadas as concentra- ções de Cu e Cr após digestão ácida. Adicionalmente, na amostra de sedimento foram determinadas as formas em que esses metais encontram-se no ambiente, por meio de um procedimento de extração sequencial. As amostras de água mostraram contaminação por Cu (0,10 – 0,17 mg L-1) e Cr (0,10 – 0,81 mg L-1). A concentração de Cu no solo coletado na região do Rio Novo, à montante do Rio Pomba, foi (69,72 mg kg-1) superior ao valor considerado como de alerta (60 mg kg-1), enquanto a de Cr em três das seis amostras de solos foi superior aos valores de alerta (75 mg kg-1). A concentração de Cr no sedimento atingiu 74,80 mg kg-1, indicando valores poluidores, embora associados à fração não disponível.Item A green and sensitive method to determine phenols in water and wastewater samples using an aqueous two-phase system(Talanta, 2009-09-04) Rodrigues, Guilherme Dias; Lemos, Leandro Rodrigues de; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol da; Minim, Luis Antonio; Coimbra, Jane Sélia dos ReisA greener and more sensitive spectrophotometric procedure has been developed for the determination of phenol and o-cresol that exploits an aqueous two-phase system (ATPS) using a liquid–liquid extraction technique. An ATPS is formed mostly by water and does not require organic solvent. Other ATPS components used in this study were the polymer, polyethylene oxide, and some salts (i.e., Li2SO4, Na2SO4 or K2HPO4 + KOH). The method is based on the reaction between phenol, sodium nitroprusside (NPS) and hydroxylamine hydrochloride (HL) in an alkaline medium (pH 12.0), producing the complex anion [Fe2(CN)10]^10− that spontaneously concentrates in the top phase of the system. The linear range was 1.50–500 μg kg^−1 (R ≥ 0.9997; n = 8) with coefficients of variation equal to 0.38% for phenol and 0.30% for o-cresol (n = 5). The method yielded limits of detection (LODs) of 1.27 and 1.88 μg kg^−1 and limits of quantification (LOQs) of 4.22 and 6.28 μg kg^−1 for phenol and o-cresol, respectively. Recoveries between 95.7% and 107% were obtained for the determination of phenol in natural water and wastewater samples. In addition, excellent agreement was observed between this new ATPS method and the standard 4-aminoantipyrine (4-AAP) method.Item Aqueous two-phase systems: An efficient, environmentally safe and economically viable method for purification of natural dye carmine(Tecnologia de Alimentos, 2009-11-09) Mageste, Aparecida Barbosa; Lemos, Leandro Rodrigues de; Ferreira, Guilherme Max Dias; Silva, Maria do Carmo Hespanhol da; Silva, Luis Henrique Mendes da; Bonomo, Renata Cristina Ferreira; Minim, Luis AntonioPartition of the natural dye carmine has been studied in aqueous two-phase systems prepared by mixing aqueous solutions of polymer or copolymer with aqueous salt solutions (Na2SO4 and Li2SO4). The carmine dye partition coefficient was investigated as a function of system pH, polymer molar mass, hydrophobicity, system tie-line length and nature of the electrolyte. It has been observed that the carmine partition coefficient is highly dependent on the electrolyte nature and pH of the system, reaching values as high as 300, indicating the high potential of the two-phase extraction with ATPS in the purification of carmine dye. The partition relative order was Li2SO4 ≫ Na2SO4. Carmine molecules were concentrated in the polymer-rich phase, indicating an enthalpic specific interaction between carmine and the pseudopolycation, which is formed by cation adsorption along the macromolecule chain. When the enthalpic carmine–pseudopolycation interaction decreases, entropic forces dominate the natural dye-transfer process, and the carmine partitioning coefficient decreases. The optimization of the extraction process was obtained by a central composite face-centered (CCF) design. The CCF design was used to evaluate the influence of Li2SO4 and PEO 1500 concentration and of the pH on the partition coefficient of carmine. The conditions that maximize the partition of carmine into the top phase were determined to be high concentrations of PEO and Li2SO4 and low pH values within the ranges studied.