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Química Nova, Volume: 37, Número: 5, Publicado: 2014
  • Catálise básica usando sílica mesoporosa estabilizada por acrilatos encapsulados Artigo

    Cruz, Fernanda Tátia; Cardoso, Dilson

    Resumo em Inglês:

    The synthesis of new type of silicas, with structures akin to that of MCM-41, containing polyacrylate-encapsulated micelles in their mesopores is reported. Initially, the monomers were inserted in the aqueous micelles of cetyltrimethylammonium cations. MCM-41 was then prepared in this microemulsion. Finally, the polymerization of the acrylates was initiated by UVC radiation. The presence of monomers and polymers in the interior of micelles in aqueous media were characterized by IR spectroscopy and small-angle Xray scattering. The presence of this polymer increased the stability of these new materials in catalytic transesterification.
  • Tratamentos térmico e químico para remoção de óxidos alcalinos de cinzas de capim elefante Artigo

    Nakanishi, Erika Y.; Villar-Cociña, Ernesto; Santos, Sérgio F.; Rodrigues, Michelle S.; Pinto, Pedro S.; Savastano Junior, Holmer

    Resumo em Inglês:

    Elephant grass ash (EGA) was produced at 700 °C, with two different treatments: hot water (EGAhw) or acid solution (EGAas). The efficiency of the treatments at removing the potassium oxide was evaluated with the aim of using the EGA as a pozzolanic mineral addition for cement-based composites. Characterizations were carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), pozzolanic activity by electric conductivity and application of the kinetic-diffusive model. The analysis evidenced that the chemical treatment was more efficient for removing potassium oxide. The pozzolanic activity test and the kinetic parameters for the EGAas indicated that this ash is suitable for cement-based composites.
  • Análise espacial e quimiométrica da distribuição de espécies metálicas em solos alagáveis e não alagáveis da Bacia do Médio Rio Negro, Amazônia Artigo

    Cordovil, Mirela Cristina de Oliveira; Mendonça, André Gustavo Ribeiro; Botero, Wander Gustavo; Santos, Ademir dos; Rocha, Julio Cesar; Mello, Kaline de; Toppa, Rogério Hartung; Oliveira, Luciana Camargo de

    Resumo em Inglês:

    This study used chemometric tools and a Geographic Information System (GIS) to determine the influence of organic matter and anthropogenic activity on the distribution of metal species between two major communities of the Middle Negro River Basin-AM. Higher concentrations of metal species were determined in flooded regions. The chemometric analysis showed the affinity of organic matter for potentially toxic metals, indicating its selectivity. GIS spatial analysis has shown that proximity to urban areas is a variable that is likely to influence the pattern of concentration of organic matter, and consequently the distribution of metal species between flooded and non-flooded areas.
  • Avaliação de diferentes métodos para a determinação de cobre em óleo mineral isolante por espectrometria de absorção atômica com forno de grafite Artigo

    Caldas, Luiz Fernando S.; de Paula, Carlos Eduardo R.; Brum, Daniel M.; Lepri, Fábio G.; Cassella, Ricardo J.

    Resumo em Inglês:

    This aim of this work was to compare two methods for copper determination in insulating oils from power transformers by GFAAS. The first method was extraction induced by emulsion breaking, which determined the preconcentration of copper in an aqueous solution and exhibited a limit of quantification of 0.27 µg L-1. Also, a second method based on the direct introduction of samples into GFAAS in the form of detergent emulsions, prepared with Triton X-114 and HNO3, was investigated. In this case, the limit of quantification was 1.7 µg L-1. Seven samples of used oils were successfully analyzed by both methods.
  • Avaliação da remoção de fármacos e de desreguladores endócrinos em águas de abastecimento por clarificação em escala de bancada Artigo

    Lima, Diego R. S.; Afonso, Robson J. C. F.; Libânio, Marcelo; Aquino, Sérgio F. de

    Resumo em Inglês:

    In this work, the efficiency of clarification treatment (coagulation, flocculation and sedimentation) with polyaluminum chloride (PAC) and aluminum sulfate (SA) as coagulants was evaluated in the removal of 7 microcontaminants (diclofenac - DCF, sulfamethoxazole - SMX, ethinylestradiol - EE2, bisphenol-A - BPA, estradiol - E2, estrone - E1 and estriol - E3) in water of low and high turbidity. The clarification treatment led to poor removal rates (40% at most) for all microcontaminants except SMX which exhibited intermediate removal efficiency (67 to 70%). Overall, PAC application yielded better performance compared to SA.
  • Avaliação da atividade antimicrobiana de soluções de flumequina submetidas aos processos eletroquímico e foto-eletroquímico Artigo

    Rodrigues-Silva, Caio; Maniero, Milena G.; Guimarães, José Roberto

    Resumo em Inglês:

    Flumequine degradation by electrochemical and photo-electrochemical processes was evaluated in this study. The antimicrobial activity of the solutions subjected to the electrochemical processes was monitored during the assays. The experiments were carried out using DSA® (dimensionally stable anode) electrode. The influence of current density was investigated for the 7.5 to 45 mA cm-2 range. The photo-electrochemical process was more efficient for degrading flumequine (85%) and reducing solution antimicrobial activity. For both processes, the residual antimicrobial activity decreased as flumequine degradation increased. The reaction intermediate m/z 244 (5-methyl-1-oxo-6,7-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-2-carboxylic acid) was identified.
  • A new approach to evaluate immobilization of β-galactosidase on Eupergit® C: structural, kinetic, and thermal characterization

    Braga, Anna R. C.; Silva, Marceli F.; Oliveira, José V.; Treichel, Helen; Kalil, Susana J.

    Resumo em Inglês:

    This study aimed to evaluate β-galactosidase immobilization. For this purpose, the ionic strength of the buffer, reaction time, amount of the immobilization support, and pH were evaluated by a central composite design. Assay 8, which consisted of 1.5 mol L-1 phosphate buffer (pH 7.5) and a reaction time of 2 h, produced the maximum yield. Eupergit® C (400 mg) was subsequently used as an immobilization support. Immobilization kinetics wereinvestigated, and a significant increase in the yield was obtained after immobilization compared with that obtained from assay 8 (22.0 U mL-1 vs. 15.6 U mL-1). The enzyme efficiency of actuation was evaluated using o-nitrophenyl-β-D-galactopyranoside and lactose, with lactose providing better results. The reuse of β-galactosidase was evaluated, and more than 50% of the initial enzyme activity was maintained after five cycles of use. Enzyme characterization revealed that immobilization improved some aspects of the thermostability of β-galactosidase.
  • Removal of Pb(II) ions and malachite green dye from wastewater by activated carbon produced from lemon peel

    Mohammadi, Sayed Zia; Karimi, Mohammad Ali; Yazdy, Sayedeh Nasibeh; Shamspur, Tayebeh; Hamidian, Hooshang

    Resumo em Inglês:

    In the present study, a high-surface area activated carbon was prepared by chemical activation of lemon peel with H3PO4 as the active agent. Then, the adsorption behavior of Malachite green dye and Pb(II) ions on the produced activated carbon was studied. Batch process was employed for sorption kinetics and equilibrium studies. Experimental data were �tted to various isotherm models. According to the Langmuir model, the maximum adsorption capacities of Malachite green dye and Pb(II) ions were found to be 66.67 and 90.91 mg g-1, respectively, at room temperature. Kinetic studies showed the adsorption process followed a pseudo second-order rate model. The sorption kinetics were controlled by intra-particle diffusion. The results indicated that the produced activated carbon can be economically and effectively used as an adsorbent for the removal of Malachite green dye and Pb(II) ions from wastewaters.
  • Análise exploratória aplicada a espectros de reflexão total atenuada no infravermelho com transformada de Fourier (ATR-FTIR) de blendas de biodiesel/diesel Artigo

    Ruschel, Carla Felippi Chiella; Huang, Chun Te; Samios, Dimitrios; Ferrão, Marco Flôres

    Resumo em Inglês:

    In this study, hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to classify blends produced from diesel S500 and different kinds of biodiesel produced by the TDSP methodology. The different kinds of biodiesel studied in this work were produced from three raw materials: soybean oil, waste cooking oil and hydrogenated vegetable oil. Methylic and ethylic routes were employed for the production of biodiesel. HCA and PCA were performed on the data from attenuated total reflectance Fourier transform infrared spectroscopy, showing the separation of the blends into groups according to biodiesel content present in the blends and to the kind of biodiesel used to form the mixtures.
  • Influência de parâmetros de processo na obtenção de sílica a partir de cinza da casca de arroz pela ação de Fusarium oxysporum Artigo

    Pineda-Vásquez, Tatiana G.; Silva, Mabel T. Born e; Soares, Carlos H. L.; Hotza, Dachamir

    Resumo em Inglês:

    In this work, an experimental design was used to analyze the influence of process parameters on the production of extracellular enzymes such as β-glucosidase and peroxidase, and their possible effect on the obtention of soluble and nanostructured silica from rice husk ash by the action of the fungus Fusarium oxysporum. Specifically, pH, fermentation time and glucose concentration in the culture medium were varied. Statistical analysis indicated that the silica synthesis in the aqueous medium was strongly dependent on pH and time. Although the glucose concentration does not exert a direct influence on the biosynthesis of silica, it is an important parameter in the production of extracellular enzymes. To prevent enzyme inhibition and provide higher dissolution of silica, it is recommended to work at a pH close to neutral with a glucose concentration of 3 g L-1 for at least 144 h.
  • Phenolic composition and antioxidant properties of Brazilian honeys

    Salgueiro, Fernanda B.; Lira, Aline F.; Rumjanek, Victor M.; Castro, Rosane N.

    Resumo em Inglês:

    The antioxidant activities and polyphenolic levels of "assa peixe," "cambara," and "morrão de candeia" Brazilian honeys were investigated. Phenolic extracts of 11 honeys were evaluated spectrophotometrically to determine their total phenolic and flavonoid contents, and their antioxidant activities were measured using DPPH, ABTS, and FRAP assays. High-performance liquid chromatography coupled with diode array detection was applied to determine the phenolic composition of the honey extracts. The presence of fourteen phenolic compounds was established (eleven phenolic acids and three flavonoids), as well as HMF and abscisic acid. Principal component analysis was applied to classify the honey samples according to their floral origins.
  • Use of multivariate experimental designs for optimizing the reductive degradation of an azo dye in the presence of redox mediators

    Lima, Diego R. S.; Baeta, Bruno E. L.; Silva, Gilmare A. da; Silva, Silvana Q.; Aquino, Sérgio F.

    Resumo em Inglês:

    The optimization of the anaerobic degradation of the azo dye Remazol golden yellow RNL was performed according to multivariate experimental designs: a 2² full-factorial design and a central composite design (CCD). The CCD revealed that the best incubation conditions (90% color removal) for the degradation of the azo dye (50 mg L- 1) were achieved with 350 mg L- 1 of yeast extract and 45 mL of anaerobic supernatant (free cell extract) produced from the incubation of 650 mg L- 1 of anaerobic microorganisms and 250 mg L- 1 of glucose. A first-order kinetics model best fit the experimental data (k = 0.0837 h- 1, R² = 0.9263).
  • DFT study on low molecular weight α,α-ditert-butyl-4H-cyclopenta[2,1-b,3;4-b']dithiophene and α,α-ditert-butyl-4H-cyclopenta[2,1-b,3;4-b']dithiophene S-oxide bridged derivatives

    Semire, Banjo; Odunola, Olusegun Ayobami

    Resumo em Inglês:

    The equilibrium geometries of α,α-ditert-butyl-4H-cyclopenta[2,1-b,3;4-b']dithiophene (DBDT) and α,α-ditert-butyl-4H-cyclopenta[2,1-b,3;4-b']dithiophene S-oxide (DBDTO) were studied at the DFT level of theory with a standard 6-311G* basis set. The molecular structures of the DBDT series were more planar than the corresponding DBDTO series, as revealed by dihedral angles. The UV-visible absorption calculated at TD-DFT/6-311G* showed two absorption peaks for all the molecules except C=S and C=O bridged molecules. In DBDTOs, C=S and C=O bridged molecules showed three and four absorption peaks, respectively. The DBDTOs had lower band gaps and longer wavelengths compared to the corresponding DBDTs.
  • Biodegradable nanoparticles obtained from zein as a drug delivery system for terpinen-4-ol

    Marini, Vanderléia G.; Martelli, Silvia M.; Zornio, Clarice F.; Caon, Thiago; Simões, Cláudia M. O.; Micke, Gustavo A.; Oliveira, Marcone A. L. de; Machado, Vanderlei G.; Soldi, Valdir

    Resumo em Inglês:

    Biodegradable nanoparticles (NPs) have received considerable attention because of their possible use in the development of strategies for the topical delivery of oils and therapeutic drugs, particularly when drug penetration in dermis is desired. Zein is a prolamine and is a promising material for the design of drug delivery systems. In this study, NPs were prepared with zein and were used to encapsulate and release terpinen-4-ol, which is a therapeutic agent for the treatment of melanoma. The results show that the zein NPs are promising nanostructured systems for the prolonged delivery of T4OL with potential applications in anti-melanoma therapy.
  • Caracterização físico-química do óleo essencial da Siparuna guianensis Aublet Artigo

    Portella, Augustus Caeser Franke; Munaro, Marilda; Ascêncio, Sergio Donizete; Siqueira, Chrystian de Assis; Ferreira, Talita Pereira de Souza; Aguiar, Raimundo Wagner de Souza

    Resumo em Inglês:

    Thermal and spectroscopic analyses of essential oil extracted from Siparuna guianensis Aublet, an aromatic plant belonging to medicinal ethnobotany family Siparunaceae, were carried out. The plant is known throughout the North and Northeast of Brazil by the name negramina and has wide application as a natural insect repellent. Thermogravimetric analyses were correlated with the Arrhenius Equation to provide kinetic parameters of evaporation, including activation energy and frequency factor. Differential scanning calorimetric analysis showed the presence of an exothermic oxidation peak, probably as a result of transformations and decomposition of the solid structure before melting.
  • Advances in ethanol reforming for the production of hydrogen

    Guerrero, Laura; Castilla, Sebastián; Cobo, Martha

    Resumo em Inglês:

    Catalytic steam reforming of ethanol (SRE) is a promising route for the production of renewable hydrogen (H2). This article reviews the influence of doping supported-catalysts used in SRE on the conversion of ethanol, selectivity for H2, and stability during long reaction periods. In addition, promising new technologies such as membrane reactors and electrochemical reforming for performing SRE are presented.
  • Produção de hidrogênio via fermentação anaeróbia - aspectos gerais e possibilidade de utilização de resíduos agroindustriais brasileiros Revisão

    Sá, Lívian R. Vasconcelos de; Cammarota, Magali C.; Ferreira-Leitão, Viridiana S.

    Resumo em Inglês:

    Biological production of hydrogen through anaerobic fermentation has received increasing attention and offers a great potential as an alternative process for clean fuel production in the future. Considering biological systems for H2 production, anaerobic fermentation stands out, primarily due to its higher production of H2 compared with other biological processes. In addition the possibility of using different agro-industrial wastes as substrates opens up infinite possibilities. The development and implementation of sustainable processes for converting renewable materials into different value-added products is essential for the full exploitation of Brazilian agro-industrial wastes.
  • Ocorrência e degradação de quinolonas por processos oxidativos avançados Revisão

    Rodrigues-Silva, Caio; Maniero, Milena G.; Peres, Marcela S.; Guimarães, José Roberto

    Resumo em Inglês:

    In this review, the presence of quinolones in the environment, their risks and the available processes for water decontamination were addressed. Their occurrence in surface waters and also in soil raises concerns about the risk of the development of resistant bacteria and other potential chronic effects. AOPs (UV/H2O2, Fenton, photo-Fenton, and UV/TiO2) and ozonation proved effective for degrading these emerging contaminants due to hydroxyl radical formation, surpassing the efficacy of conventional methods. In addition, the main degradation mechanisms of these drugs as well as data on residual biological activity were analyzed.
  • A química de coordenação e a produção de combustíveis solares Revisão

    Sousa, Sinval F.; Patrocinio, Antonio Otavio T.

    Resumo em Inglês:

    Life on earth depends on the absorption and conversion of solar energy into chemical bonds, i.e. photosynthesis. In this process, sun light is employed to oxidize water into oxygen and reducing equivalents used to produce fuels. In artificial photosynthesis, the goal is to develop relatively simple systems able to mimic photosynthetic organisms and promote solar-to-chemical conversion. The aim of the present review was to describe recent advances in the application of coordination compounds as catalysts in some key reactions for artificial photosynthesis, such as water splitting and CO2 reduction.
  • Equilibrium studies of 2,2'-(5-bromo-6-methylpyrimidine-2,4-diyl)bis(azanediyl)dipropanoic acid with some transition-metal ions in aqueous solution

    Sajadi, Seyed A. A.; Bagherzadeh, Ghodsieh; Khaleghian, Marzieh; Mirbagheri, Maryam; Safaie, Hosein

    Resumo em Inglês:

    The stability constants of the 1:1 complexes formed between M2+ (M2+: Mn2+, Ni2+, Cu2+, or Cd2+) and BMADA2- (BMADA: 2,2'-(5-bromo-6-methylpyrimidine-2,4 diyl)bis(azanediyl)dipropanoic acid) were determined by potentiometric pH titration in aqueous solution (I = 0.1 mol L-1, NaNO3, 25 °C). The stability of the binary M - BMADA complexes is determined by the basicity of the carboxyl or amino groups. All the stability constants reported in this work exhibit the usual trend, and the order obtained was Mn2+< Ni2+ < Cu2+ > Cd2+. The observed stability order for BMADA approximately follows the Irving - Williams sequence. In the M - BMADA complexes, the M ion is able to form a macrochelate via the pyrimidine group of BMADA.
  • Determinação de resíduos de agrotóxicos em leite bovino empregando método QuEChERS modificado e GC-MS/MS Nota Técnica

    Bandeira, Danieli Daiani; Munaretto, Juliana S.; Rizzetti, Tiele M.; Ferronato, Giovana; Prestes, Osmar D.; Martins, Manoel L.; Zanella, Renato; Adaime, Martha B.

    Resumo em Inglês:

    Considering the possibility that pesticides used in cattle raising produce residues in milk and cause harm to public health, this study developed a multiresidue method for determination of pesticide residues in bovine milk, using a modified QuEChERS method for sample preparation, and quantification by GC-MS/MS. The method proved to be efficient, resulting in satisfactory recoveries in the range 71.1 to 117.4%, for 45 of the 48 compounds analyzed with RSD values < 17.3%. The method LOD and LOQ were3.0 and 10.0 µg L-1, respectively, except for cyfluthrin which showed 7.5 and 25.0 µg L-1.
  • A significação conceitual pela escrita e reescrita orientada em aulas de Química Educação

    Wenzel, Judite Scherer; Maldaner, Otavio Aloisio

    Resumo em Inglês:

    In this paper, the practice of guided writing and rewriting in Chemistry classes on a graduate degree in Science is shown as a teaching method that promotes conceptual meaning in Chemistry among students. The practice examined involves writing and rewriting of texts by the students- a process guided by the teacher - about main concepts in Chemistry. The experience, follow up of classes with students' reports and the results obtained confirm that the practice of guided writing and rewriting promotes conceptual meaning in Chemistry and a good level of learning.
  • Resgatando um método eficiente para determinação do ponto de ebulição de substâncias orgânicas: percolador versus Siwoloboff Educação

    Dias, Flaviana Rodrigues Fintelman; Silva, Wanderson Amaral da; Campos, Vinícius Rangel; Cunha, Anna Claudia; Ferreira, Vitor Francisco; Souza, Nelson Ângelo de

    Resumo em Inglês:

    The aim of this paper was to revive the accurate determination of the boiling point of organic compounds using the percolator technique developed in the 1960s. Although this method is simple, fast and efficient it is omitted from current textbooks. This method has several advantages over Siwoloboff such as high reproducibility and direct measurement of the boiling point of the sample obtained by observing the temperature of the vapor-liquid equilibrium. The experiments were performed in the organic chemistry laboratory but allow interdisciplinary integration with other disciplines of several academic areas.
  • O que sabemos sobre os primeiros livros didáticos brasileiros para o ensino de Química Assuntos Gerais

    Mori, Rafael Cava; Curvelo, Antonio Aprigio da Silva

    Resumo em Inglês:

    This paper deals with the Brazilian textbooks of Chemistry from the XIX century to 1930. After presenting the science and its teaching contexts in Imperial Brazil and describing the first Chemistry textbook written by a Brazilian, the state of knowledge about these prime Brazilian books is presented. These works show the texts had strengths overlooked by current materials, a fact confirmed by analyzing textbooks from three authors from the period. The study concludes by compiling a list of 50 titles of early Chemistry books to help guide future research.
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