Sample records for ions
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1

Íons nitrênio/ Nitrenium ions

Mota, Claudio J. A.
1998-07-01

Resumo em inglês This paper reviews the chemistry of nitrenium ions, the nitrogen analogues of the carbenium ions, showing the pioneering studies and some synthetic applications.

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2

Íons carbônio/ Carbonium ions

Mota, Claudio J. A.
2000-06-01

Resumo em inglês Carbonium ions are carbocations with a pentacoordinated carbon atom, where the electronic octet is maintained. They possess a three center two electron bond in order to keep the tetravalence of the carbon atom. This paper reviews the concept of carbonium ions, their formation, stability and reactions.

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3

Efeito de íons Cu2+ e Zn2+ em atividade Ca-ATPásica isolada de larvas de Pachymerus nucleorum (Fabricius) (Coleoptera: Chrysomelidae, Bruchinae)/ Effect of Cu2+ and Zn2+ ions in Ca-ATPase activity isolated from Pachymerus nucleorum (Fabricius) (Coleoptera: Chrysomelidae, Bruchinae) larvae

Dias, Decivaldo S.; Coelho, Milton V.
2007-02-01

Resumo em português As ATPases, um importante alvo de inseticidas, são enzimas que hidrolisam o ATP e utilizam a energia liberada no processo para realizar algum tipo de trabalho celular. A larva de Pachymerus nucleorum (Fabricius) possui uma ATPase que apresenta alta atividade Ca-ATPásica, mas não expressa atividade Mg-ATPásica. Nesse trabalho, foi testado o efeito de íons zinco e cobre na atividade Ca-ATPásica dessa enzima. Mais de 90% da atividade Ca-ATPásica foi inibida em 0,5 mM (mais) de íons cobre ou 0,25 mM de íons zinco. Na presença de EDTA, mas não na sua ausência, a inibição por zinco foi revertida pelo aumento da concentração de cálcio. A inibição por íons cobre, não foi revertida nem na presença e nem na ausência de EDTA. O tratamento da fração ATPase com cobre, previamente ao ensaio de atividade ATPásica, não inibiu a atividade Ca-ATPásica sugerindo que o íon cobre não liga diretamente a enzima. Os resultados sugerem que íons zinco e cobre formam complexo com o ATP e se ligam à enzima inibindo sua atividade Ca-ATPásica. Resumo em inglês ATPases, an important target of insecticides, are enzymes that hydrolyze ATP and use the energy released in that process to accomplish some type of cellular work. Pachymerus nucleorum (Fabricius) larvae possess an ATPase, that presents high Ca-ATPase activity, but no Mg-ATPase activity. In the present study, the effect of zinc and copper ions in the activity Ca-ATPase of that enzyme was tested. More than 90% of the Ca-ATPase activity was inhibited in 0.5 mM of copper ions (mais) or 0.25 mM of zinc ions. In the presence of EDTA, but not in the absence, the inhibition by zinc was reverted with the increase of calcium concentration. The inhibition by copper ions was not reverted in the presence or absence of EDTA. The Ca-ATPase was not inhibited by treatment of the ATPase fraction with copper, suggesting that the copper ion does not bind directly to the enzyme. The results suggest that zinc and copper ions form a complex with ATP and bind to the enzyme inhibiting its Ca-ATPase activity.

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4

Adsorção de íons dicromato nos compósitos celulose/ZrO2.nH2O preparados pelos métodos da precipitação convencional e em solução homogênea/ Adsortion of dichromate ions on the cellulose/ ZrO2.nH2O composite prepared by the methods of conventional precipitation and homogeneos solution precipitation

Mulinari, Daniella Regina; Silva, Gilberto Luís J. P. da; Silva, Maria Lúcia Caetano P. da
2006-06-01

Resumo em inglês This article describes the preparation and characterization of the cellulose/ hydrated zirconium oxide composites prepared by conventional precipitation (PC) and homogeneous solution precipitation (PSH) methods. The composite obtained by the PC method was prepared by using an ammonia solution as the precipitating agent, while the composite obtained by the PSH method was prepared by using urea as the precipitating agent. The adsorption of dichromate ions on the composites (mais) was studied using factorial design 2³. The variables were: initial concentration, agitation time and mass of the composite. The data obtained agree better for the composite obtained by the PC method.

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5

Remoção de íons Zn2+, Cd2+ e Pb2+ de soluções aquosas usando compósito magnético de zeólita de cinzas de carvão/ Removal of Zn2+, Cd2+ e Pb2+ ions from aqueous solutions by magnetic composite of zeolite from coal ashes

Fungaro, Denise Alves; Yamaura, Mitiko; Graciano, José Eduardo Alves
2010-01-01

Resumo em inglês For this study, magnetic composite of zeolite-magnetite was prepared by mixing magnetite nanoparticles suspension with synthetic zeolite. The nanoparticles in suspension were synthesized by precipitating iron ions in a NaOH solution. The zeolite was synthesized from coal fly ash by alkaline hydrothermal treatment. The magnetic composite was characterized by XDR, SEM, magnetization measurements, IR, and BET surface area. Batch tests were carried out to investigate the adso (mais) rption of metal ions of Zn2+, Cd2+ and Pb2+ from aqueous solution onto magnetic composite. Adsorption isotherms were analyzed using Freundlich and Langmuir equations. The adsorption equilibrium data fitted well to the Langmuir equation with maximum adsorption capacities in the range of 28.5-127 mg g-1.

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6

Remoção de íons metálicos de soluções aquosas, por apatitas sintéticas, usando o método de troca iônica em coluna/ Removal of heavy metal ions from aqueous solutions by synthetic apatites using the column ion-exchange method

FREITAS, Jaqueline Souza de; SALOMÃO, Gisele Cantalice; GOMES, Maria de Fátima Teixeira
2000-01-01

Resumo em português Foi investigada a remoção dos íons Al3+, Mn2+, Cu2+, Zn2+, Cd2+ and Pb2 +, em solução aquosa, por apatitas sintéticas usando o método de coluna. Sob as mesmas condições, hidroxiapatitas foram mais seletivas para a remoção de cátions que carboapatitas. Usando hidroxiapatita, a capacidades de troca aumentaram na seguinte ordem: Mn2+ Resumo em inglês The removal of ions such as Al3+, Mn2+, Cu2+, Zn2+, Cd2+ and Pb2 + in aqueous solutions by synthetic apatites has been investigated using the column method. Under the same conditions, hydroyapatites were more selectives that carbonate apatites for cations remotion. Using hydroyapatites, the ranking of ions according to amount exchanged was as follows: Mn2+

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7

Adsorção de íons sulfato em ZrO2.nH2O preparado pelo método da precipitação convencional e da precipitação em solução homogênea/ Adsorption of sulfate ions in ZrO2.nH2O prepared by conventional precipitation and homogeneous solution methods

Rodrigues, L. A.; Mulinari, D. R.; Silva, M. L. C. P.
2009-03-01

Resumo em português Este trabalho visa a preparação, caracterização e estudo da adsorção de íons sulfato em óxido de zircônio hidratado preparado pelos métodos da precipitação convencional e da precipitação em solução homogênea. Os materiais obtidos foram caracterizados por difração de raios X, análise termogravimétrica, microscopia eletrônica de varredura e análise de área superficial específica pelo método BET. Através da constante Q0, relacionada com a capacidad (mais) e de adsorção máxima, observou-se que o ZrO2.nH2O/PSH possui maior capacidade de adsorção para íons sulfato que o ZrO2.nH2O/PC. Pelos resultados de ΔG, observou-se que os íons sulfato foram adsorvidos através de reações energeticamente favoráveis para toda a faixa de concentração estudada. Resumo em inglês This work reports the preparation, characterization and adsorption study of sulfate on hydrous zirconium oxides prepared by conventional and homogeneous solution precipitation methods. The materials prepared were characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and surface area measurements. Through the Q0 constant, related with the capacity of maximum adsorption, it was observed that the ZrO2.nH2O/PSH presented better adsorptio (mais) n capacity than ZrO2.nH2O/PC. By results of ΔG, it was observed that sulfate ions had been adsorbed through favorable reactions for all studied concentration ranges.

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8

Adsorção de íons cobre(II) pela quitosana usando coluna em sistema sob fluxo hidrodinâmico/ Adsorption of copper(II) on chitosan using a column in a closed hydrodynamic flow system

Guinesi, Luciana Simionatto; Esteves, Amanda Alves; Cavalheiro, Éder Tadeu Gomes
2007-08-01

Resumo em inglês The adsorption of Cu(II) ions from aqueous solution by chitosan using a column in a closed hydrodynamic flow system is described. The adsorption capacities as a function of contact time of copper(II) ions and chitosan were determined by varying the ionic strength, temperature and the flow of the metal solution. The Langmuir model reproduced the adsorption isothermal data better than the Freundlich model. The experimental kinetic data correlate properly with the second-ord (mais) er kinetic reaction for the whole set of experimental adsorption conditions. The rate constants exercise great influence on the time taken for equilibrium to be established by complexation or electrostatic interaction between the amino groups of chitosan and the metal.

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9

Influência dos Íons Mg, Ca, Fe, Cu e Zn sobre a tensão superficial estática de soluções contendo surfatante/ Influence of Mg, Ca, Fe, Cu and Zn Ions on static surface tension of surfactant solutions

Silva, F.M.L.; Velini, E.D.; Corrêa, T.M.
2006-09-01

Resumo em português O objetivo do estudo foi avaliar a influência da presença de cinco íons em uma calda de pulverização contendo o surfatante Aterbane. A tensão superficial foi analisada por meio da medição da massa de um conjunto de 25 gotas, com quatro repetições constituindo um tratamento. O trabalho foi dividido em duas etapas. Na primeira, os tratamentos foram combinados em esquema fatorial 9x5x2, sendo nove concentrações do surfatante Aterbane (0,01; 0,025; 0,05; 0,1; 0,2; (mais) 0,5; 1; 2; e 3%), cinco íons (Mg++, Ca++, Fe+++, Cu+++ e Zn+++) e duas concentrações desses elementos (10 e 100 ppm). Na segunda etapa, os tratamentos foram combinados em esquema fatorial 5x5x1, utilizandose os mesmos cinco elementos (Mg++, Ca++, Fe+++, Cu+++ e Zn+++), em cinco concentrações (1, 5, 20, 50 e 200 ppm), com apenas uma concentração do surfatante Aterbane (0,025%). Outros nove tratamentos permitiram avaliar as tensões superficiais das concentrações do surfatante (0,01; 0,025; 0,05; 0,1; 0,2; 0,5; 1; 2; e 3%) sem a adição dos íons. Os resultados mostraram que houve interferência dos íons sobre as soluções, já que, com exceção do Fe+++ (na concentração de 10 e 100 ppm) e do Cu+++ (na concentração de 100 ppm), todos os íons reduziram a tensão mínima alcançada e aumentaram a eficiência do surfatante, implicando benefícios à ação do surfatante e sobre as características de possíveis soluções de aplicação. Todos os íons avaliados promoveram reduções nas tensões superficiais de soluções do surfatante na concentração de 0,025%. Resumo em inglês The objective of this study was to evaluate the influence of 5 ions on a spray solution containing the surfactant aterbane. Surface tension was analyzed by measuring the mass of a set of 25 drops, with four repetitions constituting a treatment. The work was divided in two stages. In the first, the treatments were arranged in a 9x5x2 factorial design, nine Aterbane concentrations (0.01; 0.025; 0.05; 0.1; 0.2; 0.5; 1; 2; and 3%) and five ions (Mg++, Ca++, Fe+++, Cu+++ and Z (mais) n+++) at 2 concentrations (10 and 100 ppm). In the second stage, the treatments were arranged in a 5x5x1 factorial design using the same five elements (Mg++, Ca++, Fe+++, Cu+++ and Zn+++) at 5 concentrations (1, 5, 20, 50 and 100 ppm) with only one surfactant concentration (0.025%). Nine other treatments allowed to evaluate the surface tensions of the surfactant concentrations without ion addition. The results showed that the ions interfered in the solutions, except for Fe (at concentration of 10 and 100 ppm) and Cu (at concentration of 100 ppm), since all ions reduced the minimum tension reached and increased surfactant effectiveness, enhancing surfactant action and the characteristics of possible application solutions. All ions evaluated reduced the surface tensions of the surfactant solutions at a concentration of 0.025%.

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10

Complexação de íons de metais por matéria orgânica dissolvida: modelagem e aplicação em sistemas reais/ Complexation of metal ions by dissolved organic matter: modeling and application to real systems

Bezerra, Paulo Sérgio Silva; Takiyama, Luís Roberto; Bezerra, Cícero Wellington Brito
2009-09-01

Resumo em português Os íons de metais pesados são conhecidos tanto pela sua importância fisiológica e industrial, bem como pelo risco ambiental e à saúde humana. Para elucidar o comportamento dessas espécies nos corpos hídricos, os quais recebem grande parte da descarga de metais, seja de origem antrópica ou por fontes naturais, é necessário entender as interações que elas apresentam com o meio, principalmente a especiação química. Um dos mais importantes processos pelos quai (mais) s passam as espécies metálicas em corpos aquáticos naturais é a interação com a matéria orgânica dissolvida (MOD), que pode ser por adsorção, reações de troca iônica ou por complexação. Neste trabalho foram realizados vários experimentos com o objetivo de descrever o comportamento da complexação de três importantes cátions Cu(II), Cd(II) e Pb(II) com a matéria orgânica (ácido húmico comercial), sob condições diversas de força iônica em meio tamponado. Os resultados foram avaliados de acordo com o modelo de van den Berg e Kramer para a complexação de metais. O modelo foi aplicado na determinação da capacidade de complexação dos íons em amostras reais, oriundas de três rios maranhenses que integram a Amazônia legal: Itapecuru, Bacanga e Pericumã. Nas águas dos rios utilizou-se o parâmetro carbono orgânico dissolvido (COD) para expressar a MOD. Os resultados confirmaram forte interação entre a MOD e íons de metais pesados e que o modelo de van den Berg e Kramer é satisfatório para se estimar a constante de complexação (K) e a concentração de sítios de complexação (Lt). Nas amostras simuladas em laboratório a ordem de complexação dos metais foi Cu(II) > Cd(II) > Pb(II) e a capacidade de complexação mostrou ser linear em função da concentração de ácido húmico comercial. Acredita-se que por ter menor raio iônico, o íon Cu(II) possui maior afinidade com os sítios de complexação. Nas amostras retiradas dos corpos aquáticos, observou-se que o rio com maior concentração de COD (rio Bacanga) apresentou maior capacidade de complexação; entretanto, a ordem foi Pb(II) > Cu(II) > Cd(II) provavelmente devido à presença de íons Cu(II) em maior quantidade nas águas dos rios. Resumo em inglês Metal ions are known by their physiological and industrial importance as well as by their environmental risk aspects. To elucidate the behavior of these elements in superficial water bodies, it is necessary to understand the various occurring interactions, mainly those related to the chemical speciation. One of the most important processes that metal species undergo in natural aquatic bodies is their interaction with dissolved organic matter (DOM), which can happen throug (mais) h adsorption, ionic exchange and complexation. In this work, laboratory experiments with Cu(II), Pb(II) and Cd(II) ions and commercial humic acid were made under various conditions (ionic strength and buffering) to test the van den Berg and Kramer complexation model. After the simulation, the model was used to determine the Cu(II), Pb(II) and Cd(II) complexation capacity of natural waters from three important rivers in the state of Maranhao, Brazil (Itapecuru, Bacanga and Pericuma rivers). The dissolved organic carbon (DOC) concentration was used to express the DOM concentration. The results confirmed that there is a strong interaction between the DOM and metal ions, and that the van den Berg and Kramer model (with one coordination site) is suitable for estimating the complexation constant (K) and the ligand site concentration (Lt). The simulated water samples used in the laboratory showed the complexation order: Cu(II) > Cd(II) > Pb(II); and the complexation capacity was directly proportional to the humic acid concentration. We believe that the smaller Cu(II) ionic radius yields a stronger affinity with the DOM. In the experiments with natural waters, the river with more DOC (Bacanga river) showed better complexation capacity; however, the order was Pb(II) > Cu(II) > Cd(II) probably because of the presence of appreciable concentrations of Cu(II) in natural waters.

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11

Estudo da influência dos íons K+, Mg2+, SO4(2-) e CO3(2-) na cristalização biomimética de fosfato de cálcio amorfo (ACP) e conversão a fosfato octacálcico (OCP)/ Study of the influence of K+, Mg2+, SO4(2-) and CO3(2-) ions in the biomimetic crystallization of amorphous calcium phosphate (ACP) and conversion into octacalcium phosphate (OCP)

Aparecida, Anahí Herrera; Fook, Marcus Vinícius Lia; Santos, Márcio Luis dos; Guastaldi, Antonio Carlos
2007-08-01

Resumo em inglês The crystallization of hydroxyapatite (HA) in aqueous solution can be described by the mechanism ACP -> OCP -> HA. In this work, it was studied the influence of K+, Mg2+, SO4(2-) and CO3(2-) ions in the formation of ACP and in its conversion to OCP, using biomimetic coatings on metallic substrates of commercially pure titanium (Ti c.p.). The results showed that Mg2+ and CO3(2-) ions favored both the formation of ACP and its conversion to OCP. Differently, K+ and SO4(2-) ions did not influence the formation of ACP and, consequently, interfered in the conversion to OCP.

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12

Adsorção de íons fosfato em óxido de nióbio hidratado/ Adsorption of phosphate ions on hydrous niobium oxide

Rodrigues, Liana Alvares; Silva, Maria Lúcia Caetano Pinto da
2009-01-01

Resumo em inglês The adsorption kinetics of phosphate on Nb2O5.nH2O was investigated at initial phosphate concentrations 0.25, 0.50 and 1.00 mg.L-1. The kinetic process was described by a pseudo-second-order rate model very well. The adsorption thermodynamics was carried out at 298, 308, 318, 328 and 338 K. The positive values of both ΔH and ΔS suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. ΔG values obtained (mais) were negative indicating a spontaneous adsorption process. The Langmuir model described the data better than the Freundlich isotherm model. The effective desorption could be achieved using water at pH 12.

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13

Influência dos íons K+ e Mg2+ na obtenção de apatitas biomiméticas/ Influence of ions K+ and Mg2+ in the attainment of biomimetic apatites

Aparecida, A. H; Fook, M. V. L; Santos, M. L. dos; Guastaldi, A. C.
2005-01-01

Resumo em português O crescimento da hidroxiapatita - HA, tanto no meio biológico quanto em soluções aquosas como a Synthetic Body Fluid - SBF, ocorre em meio contendo, além dos elementos Ca e P, elementos-traços essenciais tais como: Mg2+, HCO3-, K+ e Na+. Alguns destes elementos são conhecidos como inibidores do crescimento da HA, como Mg2+ e HCO3-. Neste trabalho, estudou-se a influência dos íons K+ e Mg2+ na formação de apatitas sobre substratos metálicos de Ti c.p. previament (mais) e tratados com NaOH 5M. Os efeitos destes íons no recobrimento obtidos, antes e após o tratamento térmico a 800ºC, foram analisados por microscopia eletrônica de varredura - MEV, espectroscopia de energia dispersiva de raios-X - EDX, difratometria de raios-X - DRX e espectroscopia no infravermelho - IV e mostraram que o efeito inibitório do Mg2+ na formação da HA se manifesta após o tratamento térmico. Diferentemente, o crescimento cristalino da HA não foi afetado pela presença do íon K+. Além disso, a formação de apatita carbonatada se deu também em soluções que não continham o íon CO3(2-) em sua composição. Resumo em inglês The growth of the hydroxyapatite - HA, as much in the biological agent as in watery solutions as the Synthetic Body Fluid - SBF, occurs agent containing, beyond calcium and phosphate elements, essential element-traces such as: Mg2+, HCO3-, K+ and Na+. Some of these elements are known as inhibiting of the growth of the HA, as Mg2+ and HCO3-. In this work, it was studied the influence of ions K+ and Mg2+ in the formation of apatites, mainly of the HA, on metallic substrate (mais) of Ti c.p. previously treated with NaOH 5M. The effects of these ions in the obtained covering, before and after the thermal treatment at 800ºC, were analyzed by scanning electron microscopy - SEM, energy dispersive X-rays - EDX, X-ray diffractometer - XRD and Fourier transformation infrared - FT-IR, and they showed that the inhibitory effect of the Mg2+ in the formation of the HA happens after the thermal treatment. Differently, the crystalline growth of the HA was not affected by the presence of the K+ ion. Moreover, the carbonated apatite formation also happened in solutions that did not contain the CO3(2-) ion in its composition.

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14

Lixiviação de íons em colunas de solo deformado e indeformado/ Ions leaching in deformed and undeformed soil columns

Sampaio, Silvio C.; Caovilla, Francielle A.; Opazo, Miguel A. U.; Nóbrega, Lúcia H. P.; Suszek, Morgana; Smanhotto, Adriana
2010-02-01

Resumo em português Neste trabalho, foi avaliada a dinâmica da lixiviação de íons em colunas de solo deformado e indeformado. O solo utilizado era proveniente de área fertirrigada com água residuária da suinocultura diluída em 0%, 25%, 50%, 75% e cultivada com soja. Foram construídas curvas de eluição para nitrato, potássio e condutividade elétrica. De acordo com os resultados obtidos nas colunas de solo deformado, e proporcionalmente aos tratamentos, o nitrato apresentou maior (mais) mobilidade, seguido pela concentração de sais totais e do potássio. A metodologia de colunas de solo indeformado não se mostrou adequada, devido, possivelmente, à compactação do solo durante a amostragem e à dificuldade no bloqueio de caminhos preferenciais ao longo de toda a coluna. Resumo em inglês In this work it was evaluated the dynamics of ions leaching in deformed and undeformed soil columns. The used soil proceeded from an area irrigated with swine wastewater in different dilutions (0%, 25%, 50% and 75%) and cultivated with soybean. Breakthrough curves for nitrate, potassium and electric conductivity were constructed. According to the results, in the deformed and undeformed soil columns, the nitrate presented greater mobility, followed by the total salts and t (mais) he potassium, proportional to the treatments. The methodology of undeformed soil columns was not adequate, possibly due to the compacting during the sampling and the difficulty in the blockade of preferential ways throughout all columns.

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15

Liberação de íons por biomateriais metálicos/ Ion release from metallic biomaterials

Morais, Liliane Siqueira de; Guimarães, Glaucio Serra; Elias, Carlos Nelson
2007-12-01

Resumo em português OBJETIVO: todo biomaterial metálico implantado possui alguma interação com os tecidos em contato, havendo liberação de íons por dissolução, desgaste ou corrosão. O objetivo deste trabalho foi analisar a liberação de íons metálicos por alguns tipos de biomateriais metálicos, descrevendo a interação íon/tecido e os possíveis efeitos adversos. CONCLUSÃO: os tratamentos de jateamento e ataque ácido propiciam aumento na dissolução e liberação de íons m (mais) etálicos, mas o recobrimento destas superfícies com hidroxiapatita e o polimento eletroquímico reduzem esta tendência de liberação iônica. Na presença de sintomas de reação adversa ao biomaterial deve-se pesquisar sua composição, realizar testes de alergia e optar por materiais não-metálicos ou que não contenham o elemento agressor. As pesquisas sobre liberação de íons devem ser freqüentes, devido ao crescente lançamento de novos biomateriais. Resumo em inglês AIM: Every metallic biomaterial has some interaction with surrounding tissues, and ion release occurs by dissolution, wearing or corrosion of the alloy. The aim of this paper was to revise the metal ion release from some metallic biomaterials, describing the ion/tissue interaction and the possible side effects. CONCLUSIONS: Treatments such as sand blasting and etching increases the amount of metallic ion release, but the surface coated with hydroxyapatite and the polishin (mais) g decreases the ion release. When clinical signs of side effects to the biomaterial are present one should search its composition, do allergic tests and choose non-metallic biomaterials or biomaterials without the aggressor element. The researches about ion release should be frequent due to the use of new biomaterials.

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16

Cromatografia de afinidade por íons metálicos imobilizados (IMAC) de biomoléculas: aspectos fundamentais e aplicações tecnológicas/ Immobilized metal-ion affinity chromatography (IMAC) of biomolecules: fundamental aspects and technological applications

Bresolin, Igor Tadeu Lazzarotto; Miranda, Everson Alves; Bueno, Sônia Maria Alves
2009-01-01

Resumo em inglês Immobilized Metal Ion Affinity Cromatography - IMAC - is a group-specific based adsorption applied to the purification and structure-function studies of proteins and nucleic acids. The adsorption is based on coordination between a metal ion chelated on the surface of a solid matrix and electron donor groups at the surface of the biomolecule. IMAC is a highly selective, low cost, and easily scaled-up technique being used in research and commercial operations. A separation (mais) process can be designed for a specific molecule by just selecting an appropriate metal ion, chelating agent, and operational conditions such as pH, ionic strength, and buffer type.

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17

Importância relativa dos íons na salinidade de um cambissolo na Chapada do Apodi, Ceará/ Relative importance of ions in salinity of cambissoil at the Apodi Plateau, Ceará - Brazil

D'Almeida, Deborah M. B. A.; Andrade, Eunice M.; Meireles, Ana C. M.; Ness, Ricardo L. L.
2005-12-01

Resumo em português Este trabalho foi realizado com o objetivo de desenvolver e validar modelos em que a ordem de influência dos íons nos valores da condutividade elétrica do extrato de saturação do solo (CEes) fosse identificada. As coletas foram realizadas em duas áreas com bananeiras cultivadas sob irrigação (água subterrânea e superficial) e em áreas de vegetação nativa localizadas na Chapada do Apodi, Ceará, sendo uma em Quixeré e a outra no Distrito de Irrigação Jaguar (mais) ibe Apodi (DIJA), em Limoeiro do Norte. A pesquisa ocorreu no período de dezembro de 1999 a dezembro de 2000 e setembro a dezembro de 2001. Foram retiradas 312 amostras de solo e, por meio das análises do extrato de saturação do solo, foram determinados as CEes e os íons Na+, Cl-, Ca2++Mg2+ e K+. Posteriormente, foram desenvolvidas equações lineares múltiplas, relacionando a CEes com os íons estudados. Os modelos estatísticos desenvolvidos apresentaram valores simulados bem próximos dos observados, o que indica boa acuracidade de tais modelos. Os resultados obtidos mostraram que, em Quixeré, o íon Cl- exerce maior influência nos altos valores das CEes, seguido dos íons Ca2++Mg2+, exceto para a camada de 30-60 cm, em que o íon Na+ aparece após o Cl-. Já no DIJA, o Cl- foi predominante na camada de 0-30 cm, seguido por Ca2++Mg2+ e o Na+ na de 30-60 cm, seguido pelo Cl-. Resumo em inglês The main objective of this study was to develop and to evaluate models in order to identify the influence of ions on the values of electrical conductivity of saturation extracts (CEes). The samples were colleted in areas under irrigated banana trees (with subsurface and surface water) and native forest areas. Samples were taken in two areas in the Apodi Plateau, State of Ceara. One area was in Quixeré County and the other was at the Jaguaribe Apodi Irrigation District - (mais) DIJA, in Limoeiro do Norte County. Research was done during two periods, one from December 1999 to December 2000 and the other from September to December 2001. The 312 soil samples were taken to the laboratory for analyses of extract saturation for determination of CE and the ions Na+, Cl-, Ca2++Mg2+ and K+. A stepwise regression analysis model was tested, using CEes as the dependent variable and analyzed ions as the independent variables in all tested models. Results obtained through statistical models showed that the ion Cl- had greater influence in the elevation of the CEs values followed by the ions Ca2++Mg2+ in Quixeré. In the soil of the DIJA area, for layers of 30-60 cm, the most important ion was Na+ followed by Cl-.The linear models for the several layers, for both areas, presented a good accuracy, as the simulated values were very close to those observed.

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Obtenção de um material adsorvente para íons de metais pesados, através da eletropolimerização de 2-mercaptobenzimidazol à superfície de carbono vítreo reticulado/ Obtention of heavy metal ions adsorbent material by 2-mercaptobenzimidazole electropolimerization at reticulated vitreous carbon surface

Sousa, Maria de Fátima Brito; Dallan, Émerson José; Bertazzoli, Rodnei
2000-06-01

Resumo em inglês Electrochemical methods applied to organic species transformation has been used as excellent synthesis tools. C-C bonds can be established, making possible polymer synthesis by both anodic and cathodic reactions of suitable monomer species at the working electrode surface. In this study, anodic procedure was used to electropolymerization of 2-mercaptobenzimidazole at reticulated glassy carbon (RGC) surface. 2-mercaptobenzimidazole presents ligand sites towards Hg2+, Ag+ a (mais) nd Cu2+ ions. The obtained material has been able to adsorb the above mentioned ions in aqueous solution.

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Avaliação de metais traços e íons majoritários em águas de chuva na cidade de São Paulo/ Evaluation of trace metals and major ions concentrations in rainwater in downtown São Paulo city

Fontenele, Anna Paula Godoy; Pedrotti, Jairo J.; Fornaro, Adalgiza
2009-01-01

Resumo em inglês Rainfall samples collected in the downtown area of São Paulo city, during 2003, exhibited average concentrations of cadmium, lead and copper of 1.33, 8.52 and 49.5 nmol L-1, respectively. Among the major ions, NH4+ was the predominant species followed by NO3-, SO4(2-) and Ca2+, with volume weighed mean (VWM) concentrations of 37.1, 20.1, 11.9 and 10.8 µmol L-1, respectively. All the determined species showed high inter-events variability, including free H+ ions whose VWM concentration was 4.03 µmol L-1, corresponding to a pH value of 5.39.

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Estudo da adsorção de íons fosfato em matriz inorgânica/ Adsorption study of phosphate from aqueous solution in inorganic matrix

Rodrigues, L. A.; Silva, M. L. C. P. da
2008-03-01

Resumo em português Este trabalho visa a preparação, caracterização e estudo da adsorção de íons fosfato em óxido de tungstênio hidratado preparado pela lixiviação ácida do tungstato de sódio. Parte desse material (S1) foi tratado termicamente a 100 °C para a obtenção de um material com características diferenciadas (S1/delta). Os materiais obtidos foram caracterizados por difração de raios X, análise termogravimétrica, microscopia eletrônica de varredura e espectroscop (mais) ia de energia dispersiva. Através da constante Q0, relacionada com a capacidade de adsorção máxima, observou-se que o S1 possui maior capacidade de adsorção para íons fosfato que o S1/delta. Pelos resultados de deltaG, observou-se que os íons fosfato foram adsorvidos através de reações energeticamente favoráveis para toda a faixa de concentração estudada. Resumo em inglês This work reports the preparation, characterization and adsorption study of phosphate on hydrous tungsten oxides prepared by acid lixiviation of sodium tungstate. Part of this material (S1) was heated at 100 °C resulting in a material with differentiated characteristics (S1/delta). The materials prepared were characterized by X-ray diffraction, thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. Through the Q0 constant, related with the cap (mais) acity of maximum adsorption, it was observed that the S1 sample presented better adsorption capacity than the S1/delta. The deltaG values show that PO4-3 had been adsorbed through favorable reactions for all range of studied concentration.

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Avaliação da concentração de alguns íons metálicos em diferentes espécies de líquens do cerrado Sul-Mato-Grossense/ Evaluation of concentration of some metal ions in different lichen species of the Sul-Mato-Grossensse cerrado

Raposo Junior, Jorge Luiz; Ré-Poppi, Nilva; Honda, Neli Kika
2007-06-01

Resumo em inglês Concentrations of Fe, Mn, Co, Cr, Zn and Cu were determinated using flame atomic absorption spectrometry in nine lichen species of the Sul-Mato-Grossense cerrado. The average metal ion concentrations varied in the following ranges: Fe, 248.41-1568.01; Mn, 98.50-397.33; Co, 10.08-24.81; Cr, 18.24-44.26; Zn, 14.62-34.79 and Cu, 3.23-7.57 mg kg-1. Statistical analysis (Pearson and Cluster) applied to the metal ion concentrations indicated that the accumulation of these ions (mais) can be due to several anthropogenic sources including agricultural activities, mineral exploration, biomass burning, soil mineral composition and leather tanning processes by chromium.

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Influência do acúmulo e distribuição de íons sobre a aclimatação de plantas de sorgo e feijão-de-corda, ao estresse salino/ Influence of accumulation and distribution of ions on acclimation of sorghum and cowpea plants to salt stress

Trindade, Aldo R.; Lacerda, Claudivan F. de; Gomes Filho, Enéas; Prisco, José T.; Bezerra, Marlos A.
2006-12-01

Resumo em português Neste trabalho, estudou-se a influência do acúmulo e distribuição de íons na parte aérea de plantas de feijão-de-corda e de sorgo na aclimatação ao estresse. As plantas foram submetidas a dois tratamentos: ao controle (solução nutritiva sem a adição de NaCl ) e ao salino (solução nutritiva, contendo NaCl a 75 mM). O sorgo mostrou-se mais tolerante ao estresse salino que o feijão-de-corda, notadamente após o 10º dia de estresse. O feijão-de-corda apresen (mais) tou maior acúmulo de íons na parte aérea que o sorgo, que se comportou como planta com boa capacidade de exclusão e retenção de íons. O maior acúmulo de íons potencialmente tóxicos nos limbos foliares das plantas de feijão-de-corda, contribuiu para o aumento da suculência. Embora a exclusão ou retenção de íons em plantas de sorgo submetidas a estresse tenha produzido certo grau de desidratação foliar, pareceu tratar-se de um mecanismo de aclimatação ao estresse muito mais eficiente que o aumento da suculência resultante do acúmulo excessivo de íons nos tecidos foliares de plantas de feijão-de-corda. Resumo em inglês In this paper the influence of accumulation and distribution of ions in plant shoots on acclimation to salt stress of cowpea and sorghum plants was studied. The plants were subjected to two treatments: control (nutrient solution without addition of NaCl) and saline (nutrient solution containing 75 mM of NaCl). Sorghum showed a higher tolerance to salt stress in comparison to cowpea, mainly after the 10th day of stress. Cowpea showed higher shoot ion accumulation than sorg (mais) hum, which behaved as a plant with good capacity of ion exclusion. The higher accumulation of potentially toxic ions in cowpea leaves contributed to the increase in leaf succulence. Although the exclusion or retention of ions observed in stressed plants of sorghum had produced a certain degree of leaf dehydration, it seemed to be a much more efficient mechanism of stress acclimation than the excessive accumulation of ions in leaf tissues of cowpea plants.

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Efeito dos elementos estranhos (foreign íons) sobre a Microdureza Vickers das fases cristalinas em clínqueres co-processados/ Effect of the foreign ions on Vickers micro-hardness of the crystalline phases in the co-processed clinkers

Souza, Vládia Cristina G. de; Koppe, Jair Carlos; Costa, João Felipe Coimbra Leite
2010-06-01

Resumo em português Esse trabalho determina o valor médio de microdureza Vickers dos componentes cristalinos do clínquer e estima o efeito dos elementos estranhos (menores) e da composição mineralógica sobre os resultados de microdureza. Para isto, foi coletado um número significativo de amostras sobre a correia de alimentação de moinhos de clínqueres em onze fornos co-processadores no Brasil. Os resultados mostram que a microdureza varia de acordo com o tipo de impurezas e sua distribuição. Também, o conteúdo mineralógico e a razão alumina/ferro desempenham um papel importante. Resumo em inglês This study determines the average value of Vickers micro-hardness of the clinker crystalline compounds and evaluates the effect of foreign ions and mineralogical composition on the micro-hardness results. A significant number of samples were collected from the feed-conveyor belt of the clinker ball mill at eleven co-processing kilns in Brazil. The results show that the micro-hardness varies according to the type of impurities and their distribution. Also, the mineralogical content and alumina/iron ratio play an important role.

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Comportamento fotofísico do antraceno em sistemas micro-heterogêneos argila-surfactantes-íons metálicos

Magri, R.; Fertonani, F.L.; Pastre, I.A.
2009-12-01

Resumo em português Argilas constituem uma classe de complexos micro-heterogêneos e podem ser utilizados como substrato para adsorção. O seu comportamento de sorção em fase sólida intensificada pela presença de surfactantes, argilas organofílicas, é um importante fenômeno explorado pela tecnologia ambiental para a remoção de compostos orgânicos policíclicos (hidrocarbonetos aromáticos policíclicos, HPA) da água, introduzidos no ambiente por fontes antropogênicas. Este traba (mais) lho tem por objetivo estudar o comportamento fotofísico do antraceno, como modelo de HPA, em sistemas micro-heterogêneos argila-surfactantes-íons metálicos (M(II)= Cd(II), Cu(II), Hg(II), Ni(II) e Pb(II); surfactantes: CTACl; SDS; TR-X100). Os estudos foram conduzidos pelo monitoramento na mudança das propriedades de fluorescência estática e na supressão da emissão do antraceno utilizado como sonda fluorescente. Como supressores foram utilizados os cátions metálicos: Cd(II), Cu(II), Hg(II), Ni(II) e Pb(II). O perfil do espectro de fluorescência e os resultados dos ensaios de supressão da fluorescência da sonda permitiram inferir na localização do sítio de solubilização do antraceno nos sistemas micro-heterogêneos estudados e na conseqüente organização dos mesmos. Resumo em inglês Clays are a class of complex micro-heterogeneous and can be used as a substrate for adsorption. The sorption behavior of solid-phase enhanced by the presence of surfactants, organoclay, is an important phenomenon studied by environmental technology for removal of polycyclic aromatic hydrocarbons (PAHs) anthropogenic sources from water. This work aims to study the photophysical behavior of anthracene as a model of HPA systems in micro-heterogeneous clay-surfactant-metal io (mais) ns (M (II) = Cd (II), Cu (II), Hg (II), Ni (II) and Pb (II); surfactants: CTACl; SDS; TR-X100). The experimental assays were conducted by monitoring changes in the static properties of fluorescence and anthracene emission suppression; anthracene was used as fluorescent probe. M(II)ions, like Cd(II), Cu(II), Hg(II), Ni(II) and Pb(II)were used as anthracene fluorescence suppressors. The profile of the fluorescence spectrum and the results of the suppression of fluorescence of the probe allowed inferring the specific place of the anthracene solubilization into the micro-heterogeneous systems studied and the consequent arrangement of them.

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Estudos fotoluminescentes em compostos de íons terras raras coordenados por um derivado carbazólico/ Photoluminescence studies in rare earth ions coordinated by a carbazolic derivative

Martins, Renata Figueredo; Neri, Cláudio Roberto; Sousa Filho, Paulo Cesar de; Serra, Osvaldo Antonio; Oliveira, Kleber Thiago de
2010-01-01

Resumo em inglês [RE(czb)3(H2O)2] complexes (where RE = Eu3+, Tb3+, Gd3+; and czb = 4-(9H-carbazol-9-yl)benzoato) have been synthesized and characterized. The Gd3+ complex was used to determine the triplet state energy of the czb ligand. Photoluminescence measurements of the complexes have been carried out under UV excitation. The Tb3+ complex exhibited a strong green luminescence indicating an efficient antenna effect, whereas the Eu3+ complex showed low red luminescence and the Gd3+ com (mais) plex a blue-green luminescence from the ligand. The luminescence lifetimes and quantum yields have also been measured for the evaluation of the spectroscopic behavior of the complexes.

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Aplicação da casca de arroz na adsorção dos íons Cu2+, Al3+, Ni2+ e Zn2+/ Utilization of rice husk to remove Cu2+, Al3+, Ni2+ and Zn2+ from wastewater

Mimura, Aparecida Maria Simões; Vieira, Taciana Valéria de Almeida; Martelli, Patrícia Benedini; Gorgulho, Honória de Fátima
2010-01-01

Resumo em inglês The potential use of rice husk as biosorbent to remove Cu2+, Al3+, Ni2+ and Zn2+ ions from aqueous solutions was investigated under both noncompetitive and competitive conditions. The biosorbent was used in the form of particles with size smaller than 0.5 μm and in the concentration of 500 mg L-1 (dry weight). The experiments were performed using batch adsorption technique for concentrations of 10, 30 and 70 mg L-1 of metal ions at pH 4.0 and 5.0. The chemical speciation of metals in the experimental conditions used in this work was predicted by the software Visual MINTEQ 2.6.

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Irradiação de polímeros com feixe de elétrons: caracterização de íons positivos através da técnica de tempo-de-vôo/ Irradiation of polymers using electron beams: characterization of positive ions through the time-of-flight technique

Rocco, Maria Luiza Miranda; Pontes, Frederico Celestino; Faraudo, Gustavo Sebastian; Souza, Gerardo Gerson Bezerra de; Weibel, Daniel Eduardo; Pinho, Roberto Rosas
2004-02-01

Resumo em inglês With the aim of studying the interaction of fast electrons with solid surfaces we have developed an experimental set-up based on electron stimulated desorption (ESD) coupled to time-of-flight (TOF) mass spectrometry. Poly(methyl methacrylate) and poly(vynil chloride) samples have been irradiated by a pulsed electron beam of 1.2 keV and 0.18 µs FWHM. The results show that H+ is the main ionic species to desorb after electron bombardment. In addition, other ionic fragments (mais) were also observed and assigned. These results show the potentiality of this technique in the study of ESD of polymers.

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Preparação de membranas de acetato de celulose organomodificadas para adsorção dos íons Cu(II), Cd(II), Mn(II) e Ni(II)/ Preparation of the orgamomodified cellulose acetate membranes for adsorption of the ions Cu(II), Cd(II), Mn(II) AND Ni(II)

Goveia, Danielle; Lobo, Fabiana Aparecida; Rodrigues Filho, Ubirajara Pereira; Dias Filho, Newton Luiz; Fraceto, Leonardo Fernandes; Rosa, André Henrique
2010-01-01

Resumo em inglês Cellulose acetate polymeric membranes had been prepared by a procedure of two steps, combining the method of phase inversion and the technique of hydrolysis-deposition. The first step was the preparation of the membrane, and together was organomodified with tetraethylortosilicate and 3-aminopropyltrietoxysilane. Parameters that exert influence in the complexation of the metallic ion, as pH, time of complexation, metal concentration, had been studied in laboratory using te (mais) sts of metal removal. The membranes had presented resistance mechanics and reactivity to cations, being able to be an alternative for the removal, daily pay-concentration or in the study of the lability of metals complexed.

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Biomassa residual para remoção de íons uranilo/ Residual biomass for removal of uranyl ions

Boniolo, Milena Rodrigues; Yamaura, Mitiko; Monteiro, Raquel Almeida
2010-01-01

Resumo em inglês Activities related to nuclear industry, production of phosphoric acid and hospitals have generated considerable volumes of radioactive waste containing uranyl ions. Banana pith was characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy and was investigated as a biosorbent for uranyl ions from nitric solutions by batch experiments. Influences of adsorbent size, kinetics and equilibrium adsorption were studied. The biosorption of the urany (mais) l ions followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Freundlich equation.

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Lesões em DNA induzidas pela autoxidação de S(IV) na presença de íons metálicos de transição/ DNA damage induced by the autoxidation of S(IV) in the presence of transition metal ions

Moreno, Ruben G. M.; Alipázaga, María V.; Medeiros, Marisa H. G.; Coichev, Nina
2006-10-01

Resumo em inglês The oxidation of sulfite catalyzed by transition metal ions produces reactive oxysulfur species that can damage plasmid and isolated DNA in vitro. Among the four DNA bases, guanine is the most sensitive to one-electron oxidation promoted by the species formed in the autoxidation of sulfite (HSO5-, HO•, SO3•-, SO4•- and SO5•-) due to its low reduction potential and ability to bind transition metal ions capable to catalyze oxidative processes. Some oxidative DNA lesions (mais) are promutagenic and oxidative DNA damage is proposed to play a crucial role in certain human pathologies, including cancer.

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Desenvolvimento de um método empregando quitosana para remoção de íons metálicos de águas residuárias/ Development of a method employing chitosan to remove metallic ions from wastewater

Janegitz, Bruno Campos; Lourenção, Bruna Cláudia; Lupetti, Karina Omuro; Fatibello-Filho, Orlando
2007-08-01

Resumo em inglês In this work a method was developed for removing metallic ions from wastewaters by co-precipitation of Cu2+, Pb2+, Cd2+, Cr3+ and Hg2+ with chitosan and sodium hydroxide solution. Solutions of these metallic ions in the range from 0.55 to 2160 mg L-1 were added to chitosan dissolved in 0.05 mol L-1 HCl. For the co-precipitation of metal-chitosan-hydroxide a 0.17 mol L-1 NaOH solution was added until pH 8.5-9.5. A parallel study was carried out applying a 0.17 mol L-1 NaOH (mais) solution to precipitate those metallic ions. Also, a chitosan solid phase column was used for removing those metallic ions from wastewaters.

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Espectrometria de massas com ionização por "electrospray": processos químicos envolvidos na formação de íons de substâncias orgânicas de baixo peso molecular/ Electrospray ionization mass spectrometry: chemical processes involved in the ion formation from low molecular weight organic compounds

Crotti, Antônio Eduardo Miller; Vessecchi, Ricardo; Lopes, João Luis Callegari; Lopes, Norberto Peporine
2006-04-01

Resumo em inglês An overview of the current literature on the chemical processes involved in the ion formation from low molecular weight organic compounds by electrospray ionization mass spectrometry is given.

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Determinação experimental dos raios cristalográficos dos íons sódio e cloreto/ Determination of the crystallographic radii of sodium and chloride ions

Tubino, Matthieu; Simoni, José de Alencar
2007-01-01

Resumo em inglês This experiment, where very common materials and equipments are used, conducts to good and interesting results related to the ionic radii of sodium and chloride ions. It also offers an excellent opportunity to discuss the crystalline arrangement of solids and to apply simple mathematical tools for calculations. Other important concepts such as density, solubility and saturated solution are also used. The simplicity of the experiment creates an excellent opportunity for reasoning with the students about the technique.

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Determinação da demanda química de oxigênio em águas por espectrofotometria simultânea dos íons crômio(III) e dicromato/ Chemical oxygen demand(COD) determination in waters by simultaneous spectrophotometry of chromium(III) and dichromate ions

GRANER, Celso Augusto Fessel; ZUCCARI, Maria Lúcia; PINHO, Sheila Zambello de
1998-01-01

Resumo em português Propõe-se metodologia analítica para a determinação da demanda química de oxigênio(DQO) em águas e efluentes pouco poluídos, pela espectrofotometria simultânea dos íons crômio(III) e dicromato, após a clássica oxidação sulfocrômica das amostras, à quente e catalisada por íons Ag+. Demonstra-se que a inter-relação entre as concentrações de DQO, de crômio(III) formado e de dicromato residual permite simplificar a resolução numérica do sistema - de (mais) multicomponente, envolvendo as concentrações desses dois íons, e medidas de absorbância em pelo menos dois comprimentos de onda para monocomponente, envolvendo diretamente a concentração em DQO, e medida de absorbância num único comprimento de onda. Resumo em inglês The simultaneous colorimetry of chromium(III) and dichromate ions in a single wavelength is proposed for the determination of chemical oxygen demand(COD) in waters, after oxidation of the samples with dichromate and sulfuric acid. The interrelation among COD, chromium(III) and dichromate ions concentrations permits to simplify the numerical resolution of the system, as follow: from a multicomponent system involving chromium(III) and dichromate ions concentrations and abso (mais) rbances, in at least two wavelengths, to a linear regression involving COD concentration measured in a single wavelength. The procedure is as follows: a) mix 5 mL of standard or sample solution(30 mgL-1 - 300 mgL-1 range, using potassium hydrogenphtalat as standard) with 5 mL of digestion solution(7.000 mmolL-1 dichromate - 0.04 molL-1 mercuric sulfate - 1.5 molL-1 sulfuric acid) and 10 mL of catalytic solution(0.02 molL-1 silver sulfate - 18 molL-1 sulfuric acid); b) heath for two hours at 140 oC-150 oC; c) take absorbances against water, at 430 nm, using 1 cm length cuvettes.

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Cinética e mecanismo da reação de auto-oxidação de S(IV) catalisada por íons metálicos de transição/ Kinetic and mechanism of S(IV) autoxidation reaction catalysed by transition metal ions

Pezza, Helena Redigolo; Lopes, Cristiane F. Fernandes; Suárez-Iha, Maria Encarnación V.; Coichev, Nina
1999-07-01

Resumo em inglês The oxidation process of sulfur (IV) species (SO2, HSO3- e SO32-) by oxygen, catalysed by trace metal ion and complexes, can play an important role in atmospheric, analytical and bioinorganic chemistry. An overview of the most important reactions in these fields is presented. A fascinating redox cycling of the metal ions and complexes during such autoxidation process was revealed by the combination of kinetics and coordination chemistry studies.

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Ácido L-ascórbico: reações de complexação e de óxido-redução com alguns íons metálicos de transição/ L-ascorbic acid: complexation and redox reactions with some transition metal ions

Fornaro, Adalgiza; Coichev, Nina
1998-10-01

Resumo em inglês The strong reducing action of L-ascorbic acid (Vitamin C) are of fundamental interest in biochemical and related process. The oxidation of ascorbic acid by molecular oxygen and others oxidants are of fundamental importance, involving the intervention of transition metal ions as catalysts and the formation transition metal complexes of ascorbic acid as intermediates. The present article is intended to cover some aspects of the reactions of ascorbic acid and related compounds involving some transition metal ions.

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Usando um website para explicar a espectrometria de ressonância ciclotrônica de íons por transformada de Fourier/ Using a website to explain Fourier transform ion ciclotron resonance mass spectrometry

Xavier, Luciano Aparecido; Sena, Marcelo; Ferreira, Roberto Slepetys; Linnert, Harrald Victor; Menegon, Jair João; Souza, Luiz Augusto Gesteira de
2001-06-01

Resumo em inglês This article shows the usefulness of a website to explain the concepts, operational events, vacuum system, applications and an experimental sequence of the Fourier Transform Ion Ciclotron Resonance Mass Spectrometry technique (http://143.107.46.113/icr/icrj.html).

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Sistema aquoso bifásico: uma alternativa eficiente para extração de íons/ Aqueous biphasic systems: an efficient alternative for extraction of ions

Silva, Maria do Carmo Hespanhol da; Silva, Luis Henrique Mendes da; Paggioli, Fernanda Jürgensen; Coimbra, Jane Sélia Reis; Minim, Luis Antonio
2006-12-01

Resumo em inglês Solvent extraction has been successfully applied to metal ion preconcentration and often meant the use of toxic organic diluents. However, regulatory pressure is increasingly focusing on the use and disposal of organic solvents, and thus the development of nonhazardous alternatives is important. In this review, we examine the application of aqueous biphasic systems (ABS) to extraction of ions, analyzing their potential and limitations and suggest that ABSs could be an eff (mais) icient substitute for oil/water biphasic systems. ABSs are formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two water-soluble polymers.

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Microencapsulação do agente quelante sulfoxina em microesferas de quitosana preparadas por spray drying como novo adsorvente para íons metálicos/ Microencapsulation of the chelating agent sulfoxine into microspheres of chitosan prepared by spray drying as a new adsorbent for metalic ions

Vitali, Luciano; Laranjeira, Mauro Cesar Marghetti; Fávere, Valfredo Tadeu de; Gonçalves, Norberto Sanches
2008-01-01

Resumo em inglês In this work, a new adsorbent was prepared by microencapsulation of sulfoxine into chitosan microspheres by the spray drying technique. The new adsorbent was characterized by Raman spectroscopy, scanning electron microscopy and microanalysis of energy dispersive X-rays. The Cu(II) adsorption was studied as a function of pH, time and concentration. The optimum pH was found to be 6.0. The kinetic and equilibrium data showed that the adsorption process followed the pseudo se (mais) cond-order kinetic model and the Langmuir isotherm model over the entire concentration range. An increase of 8.0% in the maximum adsorption capacity of the adsorbent (53.8 mg g-1) was observed as compared to chitosan glutaraldehyde cross-linked microspheres.

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Emprego de sílica gel organicamente modificada e impressa ionicamente para pré-concentração seletiva on-line de íons cobre/ Employ of silica gel organically modified and ionically imprinted for selective on-line preconcentration of copper ions

Ávila, Thiago Carvalho de; Segatelli, Mariana Gava; Beijo, Luiz Alberto; Tarley, César Ricardo Teixeira
2010-01-01

Resumo em inglês The present work purposes the preparation of a silica gel sorbent organically modified with 2-aminoethyl-3-aminobutylmethyldimethoxysilane (AAMDMS) and imprinted with Cu2+ ions by means surface imprinting technique and its use for selective on-line sorbent preconcentration of Cu2+ ions with further UV-VIS spectrophotometric determination by flow injection analysis. The Cu2+-imprinted silica gel, when compared with non imprinted silica gel and silica gel, showed from the b (mais) inary mixture of Cu2+/Ni2+ relative selectivity coefficient (k') of 6.84 and 5.43 and 6.64 and 19.83 for the mixture Cu2+/Pb2+, thus demonstrating higher selectivity of Cu2+-imprinted silica gel towards Cu2+ ions. Under optimized condition, the on-line preconcentration method provided detection limit of 3.4 μg L-1 and linear range ranging from 30.0 up to 300.0 μg L-1 (r = 0.995). The accuracy of method was successfully assessed by analyzing different kind of spiked water samples with recovery values ranging from 92.2 up to 103.0%.

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Técnica de bombeio e prova para medidas de absorção de estado excitado e de emissão estimulada, em materiais sólidos dopados com íons terras raras/ Pump-probe technique for excited state absorption and stimulated emission measurements in rare earth ion doped solid materials

Camargo, Andrea Simone Stucchi de; Nunes, Luiz Antonio de Oliveira
2008-01-01

Resumo em inglês Rare earth ion doped solid state materials are the most important active media of near-infrared and visible lasers and other photonic devices. In these ions, the occurrence of Excited State Absorptions (ESA), from long lived electronic levels, is commonplace. Since ESA can deeply affect the efficiencies of the rare earth emissions, evaluation of these transitions cross sections is of greatest importance in predicting the potential applications of a given material. In this (mais) paper a detailed description of the pump-probe technique for ESA measurements is presented, with a review of several examples of applications in Nd3+, Tm3+ and Er3+ doped materials.

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Efeito do íon malato no processo de oxidação do ácido ascórbico por oxigênio molecular catalisado por íons cobre(II)/ Malate ion effect on copper(II) catalysed ascorbic acid oxidation by molecular oxygen

Silva, L. S.; Vicenzi, R.; Peixoto, C. R. M.
2007-01-01

Resumo em português Íons cobre(II) catalisam a oxidação de ácido ascórbico por oxigênio molecular. O mecanismo envolve a coordenação dos reagentes ao íon metálico. Íons malato, quando presentes, também se coordenam ao cobre(II) e inibem o efeito catalítico. As constantes cinéticas específicas (k / mol-1 L min.-1) da reação em presença de íons malato são 46,58, 7,11 e 30,00 em valores de pH de 3,5, 4,5 e 5,8, respectivamente. Existe decréscimo do valor de k com o aumento do pH de 3,5 para 4,5, o que está de acordo com a coordenação mais efetiva do malato ao cobre(II). Resumo em inglês Copper(II) ions catalyze the oxidation of ascorbic acid by molecular oxygen. The mechanism involves coordination of the reactants to the metal ion. Malate ions, when present, also coordinates to copper(II) and inhibits the catalytic effect. The specific kinetic constants (k / mol-1 L min.-1) of the reaction in presence of malate ions, are 46.58, 7.11 and 30.00 at pH 3.5, 4.5 and 5.8, respectively. The k value decreases when pH increases from 3.5 to 4.5, which is in accord with the more effectively coordination of the malate to copper(II).

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Determinação da matéria-prima utilizada na produção do biodiesel adicionado ao diesel mineral através de monitoramento seletivo de íons/ Determination of biodiesel raw materials in mineral diesel fuel using selective ion monitoring

Rocha, Daniel de Queiroz; Barros, Diana Kelly; Costa, Everton José Cardoso; Souza, Katiuscia S. de; Passos, Raimundo R.; Veiga Junior, Valdir Florêncio da; Chaar, Jamal da Silva
2008-01-01

Resumo em inglês The selective ion monitoring acquisition mode in mass spectrometry was applied to identify, in the diesel complex matrix, the raw materials (vegetable oil and alcohol) that originate biodiesel. Biodiesel samples obtained from babassu, castor, palm and soybean vegetable oils and pure fatty acid methyl and ethyl esters were used to develop this method, using specific fragments in mass spectrometry and the "window system" in gas chromatography. The commercial Brazilian B2 samples were found to be produced with soybean oil, transesterified with methanol.

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Remoção do íon amônio de águas produzidas na exploração de petróleo em áreas offshore por adsorção em clinoptilolita/ Removal of ammonium ions from waters produced in petroleum offshore exploitation by adsorption on clinoptilolite

Lima, Rosilda Maria Gomes de; Wildhagen, Glória Regina da Silva; Cunha, José Waldemar Silva Dias da; Afonso, Julio Carlos
2008-01-01

Resumo em inglês This work describes the use of clinoptilolite for removal of ammonium ions present in waters produced at the Campos' Basin. Samples were previously treated in order to remove organic compounds and metals. Experiments were run in fixed- and fluidized-bed systems, at room temperature. The fluidized-bed systems did not remove efficiently the ammonium ion. The best operational conditions were obtained with clinoptilolite particle size in the range 0.30-0.50 mm, under ascendan (mais) t flow (3 mL min-1), in a fixed-bed system. The best zeolite performance was found when it was pretreated with 0.5 mol L-1 NaOH. Na+ was the most important interfering ion due to its high concentration in the water. Clinoptilolite lost partially its capacity to retain ammonium ions after several regeneration cycles with NaOH.

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Construção artesanal de um eletrodo íon seletivo a chumbo(II): uma alternativa para disciplinas experimentais/ Homemade construction of a lead(II) ion selective electrode: an alternative to experimental subjects

Silva, Jonatas Gomes da; Lehmkuhl, Arilson; Alcanfor, Silvia Keli de Barros
2009-01-01

Resumo em inglês This works proposes a homemade construction of a lead(II) ISE of solid membrane (Ag2S/PbS) to determine Pb2+ ions in potentiometric titrations, using damaged combined glass electrodes. This electrode can be constructed in teaching laboratories, using it as a learning tool related to the theoretical principle of ISE. The analytical curve obtained (y = 27.056x + 337.58; R = 0.996) was linear on the range of 1 x 10-5 to 1 mol L-1 and has presented a very close behavior of th (mais) e Nernstian. The homemade ISE has presented a similar selectivity to the commercial electrodes, showing to be a good alternative to the experimental activities on teaching laboratories.

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Determinação de parâmetros físico-químicos com um sensor potenciométrico sensível ao íon p-aminobenzoato/ Determination of physical chemical parameters with a potentiometric sensor sensitive to p-aminobenzoate ion

Santini, A. O.; Silva Júnior, E. S. da; Pezza, H. R.; Pezza, L.
2004-01-01

Resumo em português Este trabalho descreve a construção e a determinação de parâmetros físico-químicos com um eletrodo de segunda ordem do tipo, Pt|Hg|Hg2(PAB)2|Grafite, sensível ao íon p-aminobenzoato (PAB). O eletrodo é construído facilmente, apresenta um rápido tempo de resposta, é de baixo custo e tem um tempo de vida útil superior a 12 meses. Utilizando o referido eletrodo foi possível estimar os coeficientes de atividade iônica individuais do PAB, a 25ºC, em força iô (mais) nica ajustada entre 0,700-3,000 mol L-1 com NaClO4, em solução aquosa. O potencial molal padrão do eletrodo determinado a 25ºC é de (445,5 ± 0,5) mV. A constante termodinâmica do produto de solubilidade, T Kps (I=0) do Hg2(PAB)2 determinada com o eletrodo é de (T Kps = 2,50 x 10-12 mol³ L-3 , a 25ºC). Uma característica favorável consiste no fato de que o eletrodo pode ser utilizado para determinar a concentração de íons p-aminobenzoato livres em sistemas complexos de íons metálicos. Resumo em inglês The paper describes the construction and determination of physical chemical parameters with a second kind electrode, Pt|Hg|Hg2(PABA)| Grafite, sensitive to p-aminobenzoate ion (PAB). Electrode construction is easy, presents a fast response time (30 sec), low-cost, excellent response stability and (lifetime > 12 months, under continuous use). Using of the mercury(I) p-aminobenzoate electrode, the molar single activity coefficient associated with PAB (yPAB) was estimated at (mais) 25ºC and ionic strengths between 0.700-3.000 mol L-1 (NaClO4). The standard molal potential of the electrode at 25ºC is 445.5 ± 0.5 mV. The thermodynamic solubility-product constant of mercurous p-aminobenzoate determined with the mentionated electrode , in aqueous solution, at 25ºC was T Kps = 2.50 x 10-12 mol³ L-3 . An important feature of the electrode is that it permits the determination of the concentration of free p-aminobenzoate ions in complex systems of metallic ions.

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Dióxido de chumbo eletrodepositado sobre grafite como sensor potenciométrico à ions chumbo e sulfato/ Electrodeposited lead dioxide about graphite as potenciometric sensor to the ions lead and sulphate

CASSIANO, Neila Maria; RAMOS, Luiz Antônio; CAPELATO, Milton Duffles
2001-01-01

Resumo em português No presente trabalho, foi desenvolvido um eletrodo de PbO2 eletrodepositado sobre grafite a partir do eletrólito metanosulfonato de chumbo-ácido metanosulfônico contendo o agente tensoativo brometo de cetiltrimetilamônio (BCTA). Foram avaliadas a resposta potenciométrica do eletrodo de PbO2 como sensor à íons Pb2+ e SO4(2-), em pH e força iônica constante. A aplicação deste eletrodo em titulações potenciométricas de precipitação em meio hidro-etanólico ta (mais) mbém foi investigada. Os resultados demonstraram que o eletrodo de PbO2 eletrodepositado pode ser utilizado como sensor potenciométrico alternativo à íons Pb(II) apresentando uma linearidade na faixa de concentração de 3,98x10-4 a 3,09x10-2 mol L-1 em meio de íons nitrato com limite de detecção de (4,98 ± 0,11)x10-4 mol L-1. Para íons sulfato o eletrodo de PbO2 não responde diretamente porém, estes íons podem ser dosados indiretamente por titulação potenciométrica com solução padrão de Pb(II), em meio ácido, em uma mistura 1:1 (v/v) de etanol-água, com boa definição dos volumes de equivalência. A repetitividade dos potenciais e dos volumes de equivalência obtidos em amostras de concentração milimolar em sulfato, indicam a viabilidade deste eletrodo na dosagem de íons sulfato. Resumo em inglês The development of a PbO2 electrodeposited in a graphite substrate electrode and evaluation of its potenciometric response as a sensor for Pb2+ and SO4(2-) ions, at constant pH and ionic strength is described. The electrode was applicated in the potenciometric titration in precipitation reaction of Pb2+ with SO4(2-) in hydro-ethanolic medium. The results showed that the PbO2 electrodeposited electrode is useful as a potenciometric sensor to the Pb(II) ions presenting a li (mais) near response range between 3,98x10-4 a 3,09x10-2 mol L-1 in nitrate medium, with a practical detection limit of (4,98 ± 0,11)x10-4 mol L-1. For sulphate ions the PbO2 electrode did not responded directly. These ions might be dosed indirectly by potentimetric titration with standard Pb(II) solution in acidic media, in 1:1 ethanol-water (v/v), with good definition of the equivalence volumes. The reprodutibilidade of the potenciais and of the equivalence volumes obtained in samples with concentration at milimolar level in sulphate, indicate the possibility of the use of this electrode in quantifying sulphate ions.

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Determinação de Cd por FAAS em meio aquoso após pré-concentração em linha sobre SiAT/ Determination of Cd (II) by FAAS in aqueous medium after preconcentration in line on a SiAT

Moraes, F. V.de; Alcântara, I. L. de; Roldan, P. dos S.; Castro, G. R. de; Margionte, M. A. L.; Padilha, P. de M.
2003-01-01

Resumo em português Este trabalho descreve a síntese e caracterização da sílica gel modificada com grupos 2-aminotiazol (SiAT), os resultados de um estudo de adsorção e de pré-concentração (em batelada, e em fluxo utilizando-se a técnica de coluna) de íons Cd(II) em meio aquoso. A capacidade máxima de adsorção de íons Cd(II) determinada para SiAT foi de 1,12 mmol g-1 . Os resultados obtidos nos experimentos em fluxo, mostraram uma recuperação de 98% dos íons Cd(II) adsorvid (mais) os em coluna empacotada com 1 g de SiAT, utilizando-se 5 mL de HCl 1 mol L-1 como eluente. A metodologia proposta mostrou-se linear na faixa de concentração de 10 - 100 mg L-1, com limite de detecção de 0,80 mg L-1 e desvio padrão relativo de 3%. O fator de enriquecimento determinado foi de 29 vezes (considerando-se a percolação de 150 mL de solução 25 mg L-1 de Cd(II), 5 mL de eluato). A sorção-desorção quantitativa dos íons Cd(II), permitiram a aplicação do método na pré-concentração e posterior quantificação de traços de Cd(II) em amostras de águas naturais por espectrometria de absorção atômica com chama. Resumo em inglês This paper described the preparation of 2-aminothiazole modified silica gel (SiAT) and the results of a study of the sorption and preconcentration (in batch and in flow using a column technique) of Cd(II) in aqueous medium. The sorption capacities for metal ion was 1.12 mmol g-1. The results obtained in the flow experiments, showed a recovery of 98% of Cd(II) adsorbed in a column packed with 1 g of SiAT, using 5.0 mL of 2.0 mol L-1 hydrochloric acid as eluent. An enrichme (mais) nt factor of 25 (150 mL solution containing 25 mg L-1 of Cd(II), 5.0 mL concentrated) was obtained by this preconcentration procedure. The sorption-desorption of Cd(II) made possible the development of a preconcentration method and quantification by Flame AAS of Cd(II) at trace level in aqueous samples.

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Remoção de compostos tóxicos de solução aquosa por adsorção com zeólita sintetizada a partir de cinzas de carvão/ Removal of toxics compounds from aqueous solution by adsorption with zeolite synthesized from coal ashes

Fungaro, D. A.; Izidoro, J. C.; Almeida, R. S.
2005-01-01

Resumo em português A capacidade das zeólitas sintetizadas a partir da cinza de carvão brasileiro na remoção dos íons de Cd, Zn e do azul de metileno de soluções aquosas foi investigada. O material zeolítico preparado com a cinza de carvão do filtro manga apresentou a eficiência de remoção mais alta para os poluentes. A seletividade aos íons metálicos deste produto foi determinada como: Cd2+ > Zn2+. As capacidades máximas de adsorção encontradas foram 36,1 mg g-1 para o Zn2+, 76,3 mg g-1 para o Cd2+e 3,93 mg g-1 para o corante. Resumo em inglês The capacity of synthesized zeolites from Brazilian coal ash for the removal of Cd, Zn ions and methylene blue from aqueous solutions has been investigated. The zeolitic material prepared with coal ash from baghouse filter showed the highest efficiency for pollutants removal. The metal ion selectivity of this product was determined as: Cd2+ > Zn2+. The maximum sorption capacities found were 36.1 mg g-1 for Zn2+, 76.3 mg g-1 for Cd2+ and 3.93 mg g-1 for dye.

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Magnetita para fixação de compostos tóxicos solubilizados de resíduos de fundição de chumbo/ Using magnetite to fix toxic compounds solubilized from solid residues produced at lead smelting plant

Godoi, Evelyn Loures de; Garcia, Priscila Moreira Peres; Ortiz, Nilce
2007-09-01

Resumo em português Um resíduo siderúrgico composto basicamente por magnetita (Fe3O4) foi estudado como material adsorvente para fixação de íons metálicos presentes nos produtos lixiviados e solubilizados de secundários da unidade desativada de fundição de chumbo - Panelas, localizada na Bacia do Rio Ribeira de Iguape. Os leitos adsortivos preparados com a mistura Magnetita, Bentonita e Cinzas - MBC apresentaram 71,4% de remoção de íons de chumbo e 26,9% de remoção de íons de (mais) zinco adicionados em concentrações semelhantes às medidas nos produtos lixiviados e solubilizados do secundário de fundição. Os valores de velocidade de adsorção obtidos foram proporcionais aos citados para adsorventes não convencionais em literatura e as equações propostas no modelo empírico apresentaram correspondência com os valores obtidos experimentalmente. Resumo em inglês Metallurgic waste mainly composed by magnetite (Fe3O4) was studied to be used as adsorber material to fix the metallic ions present as leached and solubilizated products of smelting plant residues deposited at the decommissioned plant called Panelas, located at the Ribeira de Iguape River Basin. The adsorption beds prepared with Magnetite, Bentonite and Ashes (MBC) show 71,4 % of removal percentage for lead ions and 26,9% for zinc ions added in similar initial concentrati (mais) ons with those found for solubilized and leached products, measured from smelting solid residues. The obtained adsorption velocities were similar with those found in the literature for non conventional adsorbers and the equations proposed for the empirical model shows correspondence with the experimental values.

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Aplicação de material zeolítico sintetizado de cinzas de carvão como adsorvente de poluentes em água/ Application of zeolitic material synthesized from coal ashes as adsorbent for pollutants from water

Fungaro, D. A.; Izidoro, J. C.; Bruno, M.
2009-01-01

Resumo em português Cinzas leve de carvão tratadas pelo método hidrotérmico foram usadas como adsorvente de baixo custo para a remoção de íons metálicos e corante de solução aquosa. As isotermas de adsorção das cinzas leve tratadas foram estudadas e os resultados foram ajustados pelos modelos de Langmuir e Freundlich. A isoterma de Freundlich descreveu melhor o processo de adsorção do azul de metileno. Os dados de equilíbrio para a adsorção dos íons zinco e cádmio se ajusta (mais) ram melhor á equação de Langmuir. O valor máximo de capacidade de adsorção obtido foi de 0,78 (mg g-1)(L mg)1/n para o azul de metileno, 38,1 mg g-1 para o Zn2+ e 67, 5 mg g-1 para o Cd2+. Os materiais sintetizados exibiram capacidades de adsorção muito maiores do que as das cinzas leves usadas como matéria-prima. O estudo mostrou que o material zeólitico pode efetivamente adsorver azul de metileno e íons metálicos com eficiências de remoção na faixa de 82-99%. Resumo em inglês Coal fly ashes treated by hydrothermal method were used as low-cost adsorbent for the removal of metals ions and dye from aqueous solution. The adsorption isotherms of the treated fly ashes were studied and results were fitted using Langmuir and Freundlich models. It shows that the Freundlich isotherm is better in describing the adsorption process for methylene blue. The equilibrium data for zinc and cadmium ions adsorption well fitted to the Langmuir equation. The maximu (mais) m adsorption capacity value obtained was 0.78 (mg g-1)(L mg)1/n for methylene blue, 38.05 mg g-1 for Zn2+ and 67.48 mg g-1 for Cd2+. The synthesized materials exhibit much higher adsorption capacities than raw fly ashes. The study showed that the zeolitic material can effectively adsorb methylene blue and metals ions with removal efficiencies ranging from 82-99%.

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Extração da lectina da folha de mandioca (Manihot esculenta Crantz) e o efeito de cátions divalentes na atividade hemaglutinante/ Extraction of the lectin of cassava leaves (Manihot esculenta Crantz) and the effect of divalent cations on the hemagglutinating activity

Silva, Maria Cristina; Corrêa, Angelita Duarte; Santos, Custódio Donizete dos; Marcos, Flávia Cristina Almeida; Abreu, Celeste Maria Patto de
2010-05-01

Resumo em português Lectinas são proteínas ligantes de carboidratos, capazes de aglutinar eritrócitos, podendo exercer ação antinutricional. O isolamento destas proteínas tóxicas é interessante tanto pela sua ação antinutricional, como pela sua aplicação em biotecnologia. Algumas lectinas necessitam da presença de íons divalentes para exercer sua atividade hemaglutinante (AH). O objetivo neste trabalho foi estudar diferentes métodos de extração da lectina da farinha de folha (mais) s de mandioca (FFM) e avaliar o efeito dos íons Ca2+ e Mn2+ para sua AH. Foram feitos testes de extração das proteínas utilizando dois extratores, água e solução salina (0,15 mol.L-1, pH 7,4), em quatro tempos de extração, 15, 60, 120 e 180 minutos. Para avaliar o efeito dos íons Ca2+ e Mn2+ na AH da lectina da FFM, o extrato proteico foi dialisado contra EDTA e a AH determinada. O efeito desses cátions na aglutinação de hemácias também foi avaliado isoladamente. O método de extração proteica usando água destilada como extrator por 15 minutos é o mais adequado. Não houve perda da AH na ausência dos íons. Os cátions Ca2+ (5 mmol.L-1), Mn2+ (1, 3 e 5 mmol.L-1) e a mistura de ambos nas mesmas concentrações provocam aglutinação de hemácias, na ausência de lectina. Resumo em inglês Lectins are carbohydrates binding proteins, capable of agglutinating erythrocytes, which can act as anti-nutritional factors. The isolation of these toxic proteins is interesting both for its anti- nutritional action and for its application in biotechnology. Some lectins need the presence of divalent ions to express hemagglutinating activity (AH). The objective of this work was to investigate different methods of extracting lectins from cassava leaf flour (CLF) and to eva (mais) luate the effect of the ions Ca2+ and Mn2+ on the AH. Protein extraction tests were performed utilizing two extractors, water and saline solution (0.15 mol.L-1, NaCl pH 7.4), under four extraction times, 15, 60, 120, and 180 minutes. To evaluate the effect of the ions Ca2+ and Mn2+ on the AH of CLF lectin, the protein extract was dialyzed against EDTA and the AH was determined. The effect of the cations upon the agglutination of red blood cells was also evaluated individually. The protein extraction method utilizing water as extractor under 15 minutes was the most suitable. No loss of AH was found in the absence of the ions. The cations Ca2+ (5 mmol.L-1), Mn2+ (1, 3 and 5 mmol.L-1), and the mixture of both under the same concentrations provoked agglutination of red blood cells in the absence of lectin.

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Determinação de chumbo em álcool combustível por voltametria de redissolução anódica utilizando um eletrodo de pasta de carbono modificado com resina de troca iônica Amberlite IR 120/ Lead ions determination in ethanol fuel by differential pulse anodic stripping voltammetry using a carbon paste electrode modified with ion-exchange resin Amberlite IR120

Bergamini, M. F.; Vital, S. I.; Santos, A. L.; Stradiotto, N. R.
2006-01-01

Resumo em português Um método envolvendo a pré-concentração e redissolução anódica em condições de voltametria de pulso diferencial empregando um eletrodo de pasta de carbono modificado (EPCM) com uma resina de troca iônica Amberlite IR120 foi proposto para a determinação de íons chumbo em álcool combustível. O procedimento é baseado em um pico de oxidação do analito observado em -0,53 V(vs. Ag/AgCl) em solução de HCl. As melhores condições experimentais encontradas for (mais) am: 5% (m/m) da Amberlite IR120 para a construção do eletrodo, solução de HCl 0,1 mol L-1, velocidade de varredura de 10 mVs-1, tempo de pré-concentração de 15 min e amplitude de pulso de 100 mV. Utilizando essas condições, o EPCM apresentou uma resposta linear entre a corrente de pico anódica e a concentração de íons chumbo para o intervalo entre 9,9 x 10-9 e 1,2 x 10-6 mol L-1 e um limite de detecção de 7,2 x 10-9 mol L-1. Valores de recuperação entre 96 % e 102 % foram encontrados para amostras de álcool combustível enriquecidas com Pb2+ em níveis de 10-7 mol L-1. O efeito da presença de outros íons concomitantes sobre a resposta voltamétrica do eletrodo também foi avaliado. Resumo em inglês The use of pre-concentration and differential pulse anodic stripping voltammetry (DPASV) using a carbon paste electrode modified (CPEM) with ion-exchange resin (Amberlite® IR120) has been proposed for the determination of lead ions content in ethanol fuel. The lead oxidation peak was observed at -0.53 V (vs. Ag/AgCl) in HCl solution. The best DPASV response was reached for an electrode composition of 5% (m/m) Amberlite® IR120 in the paste, 0.1 mol L-1 HCl solution, scan (mais) rate of 10 mVs-1, pre-concentration time of 15 min and potential pulse amplitude of 100 mV. In these experimental conditions, the proposed methodology responds to lead ions in the concentration range of 9.9 x 10-9 to 1.2 x 10-6 mol L-1 with a detection limit of 7.2 x 10-9 mol L-1. Recoveries ranged from 96 to 102 % for Pb(II) spiked in an ethanol fuel sample at 10-7 mol L-1 level were achieved. Interferences were also evaluated.

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Reatividade in vitro de lipase submetida a diferentes tratamentos tecnológicos/ Reactivity in vitro of the lipase submitted to different technological treatments

Ferreira, V.P.A.; Ferreira, W.M.; E.O.S., Saliba; Teixeira, A.O.
2005-06-01

Resumo em português Analisou-se a atividade enzimática in vitro de uma lipase em diferentes condições de temperatura (simulando o processo de peletização) e pH (acidez gástrica) e na presença de íons minerais e metálicos. Para avaliar a estabilidade térmica, a enzima foi incubada a 80(0)C por quatro tempos (0, 5, 10 e 15 minutos). O efeito do pH foi estudado submetendo-se a enzima a quatro valores de pH (7,3, 2,0, 3,2 e 5,0). Para avaliar o efeito da lipase na presença de íons mi (mais) nerais e metálicos, incubou-se a enzima em diferentes soluções contendo cálcio, cobre, cobalto, manganês e ferro. Frente às diferentes condições, a lipase conservou atividade parcial, mas não pôde ser considerada uma enzima ideal em função do efeito inibidor promovido pelo pH ácido e pelas soluções iônicas testadas. Resumo em inglês The in vitro catalytic activity of a lipase was assessed in different conditions of temperature (simulating that of pelleted ration manufacturing), pH (gastric acidity), and its stability in the presence of metallic and mineral ions. To assess the thermal stability, the enzyme was incubated for 0, 5, 10 or 15 minutes at 80ºC. The effect of pH was studied by submitting the lipase to pH values of 7.3, 2.0, 3.2 or 5.0. In order to evaluate the catalytic activity in the pres (mais) ence of metallic and mineral ions, the enzyme was incubated in solutions containing calcium, copper, cobalt, manganese and iron. In the above mentioned conditions, the lipase partially preserved its activity, but, could not be considered an ideal enzyme due to its inhibition by the acidic pH and the ionic solutions tested.

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Aplicação de Al-PILC na adsorção de Cu2+, Ni2+e Co2+ utilizando modelos físico-químicos de adsorção/ Aplication of al-pilc in the adsorption of Cu2+, Ni2+e CO2+ using adsorption physico-chemical models

Guerra, D. L.; Airoldi, C.; Lemos, V. P.; Angélica, R. S.; Viana, R. R.
2007-01-01

Resumo em português Amostra de esmectita pertencente a Serra de Maicuru (Estado do Pará, Norte do Brasil, região amazônica) foi pilarizada com Al13, A Argila pilarizada com alumínio (Al-PILC) foi caracterizada por DRX, MEV e EDS. Para a análise textural foram utilizadas isotermas de adsorção-desorção utilizando o nitrogênio. Este artigo é dirigido ao estudo da adsorção de metais pesados. A adsorção dos íons de Cu2+, Ni2+e Co2+ foi realizadas com a matriz Al-PILC em temperatur (mais) a ambiente com soluções aquosas contendo os íons metálicos. Os modelos de adsorção adotados foram os de Langmuir, Freundlich e Temkin que foram aplicados aos valores obtidos experimentalmente com regressão linear. A equação de Langmuir foi o melhor modelo de linearização com r = 0,999. A equação de Freundlich apresentou limitações em altas concentrações, mas foram obtidos valores (Kf e n) bastante aceitáveis utilizando este modelo. Os parâmetros foram utilizados para calcular a quantidade de Nf em função de Cs. Resumo em inglês Smectite sample from the Serra de Maicuru area (Pará state, northern Brazil, Amazon region) were used for the pillaring process with Al13. Aluminum pillared clay (Al-PILC) was characterized by XRD, SEM and EDS. the textural analysis using nitrogen adsorption-desorption isotherms. The aim of this paper is to study in how Al-PILC adsorb heavy metals. The adsorption of Cu2+, Ni2+, Co2+ ions from aqueous solution in room temperature by Al-PILC have been carried out. The Lang (mais) muir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data, with the first model well adjusted with r = 0.999. The one-surface Langmuir equation provided the best fit to the data. The Freundlich equation presented limitations in rises concentrations, but acceptable values of parameters were obtained (Kf and n) with the use of the three models. The parameters were used to calculate the amount adsorbed Nf, a function constant Cs.

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Eletrodo modificado em filme de paládio para a determinação voltamétrica de fosfito/ Modified electrode with palladium film for voltammetric determination of phosphite

Ito, Helenice Akemi; Oliveira, Marcelo Firmino de; Gomes Neto, José Anchieta; Stradiotto, Nelson Ramos
2002-01-01

Resumo em português Os íons fosfito constituem um importante componente inorgânico como fonte de fósforo na fertilização de solos, apresentando incontáveis vantagens em relação ao fosfato. A determinação desse ânion em produtos fertilizantes é usualmente realizada empregando-se método clássico de análise como gravimetria, sob a forma de pirofosfato de magnésio ou pela formação de cloreto mercuroso. Entretanto, existem algumas desvantagens nesta metodologia, como a necessida (mais) de de um elevado tempo de digestão e a possível produção de resíduos tóxicos. Sendo assim, este trabalho teve como objetivo propor uma metodologia eletroquímica alternativa para a determinação de fosfito. A modificação eletroquímica na superfície de eletrodos de platina realizada por eletrodeposição de paládio apresentou efeito catalítico para a oxidação de íons fosfito a fosfato em meio de ácido sulfúrico 1,0 mol.L-1. Uma dependência linear em relação à concentração de fosfito foi obtida no intervalo de 5,0x10-6 a 5,0x10-4 mol.L-1 tendo uma sensibilidade amperométrica de 8,5x10(4) miA.mol-1.L e um limite de detecção de 3.67x10-6 mol.L-1. Resumo em inglês Phosphite ions constitute an important inorganic component as phosphorus source in soil fertilization, showing a large number of advantages in relation to phosphate. The determination of this compound in fertilizing products is realized by classical methods of analysis as gravimetry, in the form of magnesium pyrophosphate or by mercurous chloride formation. However, there are some disadvantages in these methods as the necessity of high times of digestion and possible toxi (mais) c residue production. So, this work has the objective to propose an alternative electrochemical method for phosphite determination. Electrochemical modification on electrode surface by electrodeposition of palladium has exhibited catalytic effect for oxidation of phosphite to phosphate ions in 1,0mol.L-1 sulfuric acid aqueous medium, being obtained a linear dependence in relation to phosphite concentration from 5,0x10-6 to 5,0x10-4 mol.L-1 with an amperometric sensibility of 8,5x10(4) muA.mol-1.L and a detection limit of 3.67x10-6 mol.L-1. In the absence of palladium film on platinum electrode no anodic peak current is observed for phosphite oxidation.

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Análise de registros eletrocardiográficos associados ao infarto agudo do miocárdio/ Analysis of electrocardiographic recordings associated with acute myocardial infarction

Mansur, Paulo Henrique Garcia; Cury, Lacordaire Kemel Pimenta; Destro-Filho, João Batista; Resende, Elmiro Santos; Destro, José Paulo Breda; Oliveira, Luana Michelli de; Moraes, Diego Carvalho Gomes de; Freitas, Geraldo Rubens Ramos de; Rocha, Lucila Soares da Silva
2006-08-01

Resumo em português OBJETIVO: Avaliar correlações entre as variações do eletrocar­diograma (ECG) e o infarto agudo do miocárdio. MÉTODOS: Uso de software de baixo custo para digitalização de ECG impressos e/ou em formato "pdf". Cálculo de área do segmento ST e das amplitudes dos pontos J e Y RESULTADOS: A amplitude do ponto Y possui máxima correlação com a concentração da enzima troponina. O supradesnivelamento do segmento ST não se constitui bom indicador estatístico da gr (mais) avidade do infarto. Existe uma forte correlação negativa entre a amplitude do ponto J e a quantidade de íons magnésio, mas nenhuma correlação estatística com os íons sódio ou cálcio. Os dois métodos de cálculo da área do segmento ST (contagem de pixels e interpolação) não mostraram diferenças significativas nos resultados. CONCLUSÃO: O software utilizado mostrou-se viável do ponto de vista econômico e funcional. A amplitude do ponto Y é um marcador sensível à ocorrência do infarto, tendo cálculo mais simples e menos sujeito a erros do que o cálculo da área de supradesnivelamento do segmento ST. Resumo em inglês OBJECTIVE: Evaluate correlations between variations in eletrocardiogram (ECG) recordings and acute myocardial infarction. METHODS: Use of a low-cost software to digitalize printed and/or ".pdf" file format ECG recordings. Calculation of ST-segment area and amplitudes of the J and Y points. RESULTS: The amplitude of the Y point holds maximum correlation with troponin concentration. ST-segment elevation is not a good statistical indicator of myocardial infarction severity. (mais) There is a strong negative correlation between the amplitude of the J point and the amount of magnesium ions, but no statistical correlation with sodium or calcium ions. Neither method for calculating the ST-segment area (pixel counts and interpolation) indicated any significant differences in the results. CONCLUSION: The software used proved to be functional and cost-effective. Y point amplitude is a sensitive marker of myocardial infarction, and is also a calculation method both simpler to use and less subject to error than the calculation of the ST-segment elevation area.

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Influência da salinidade sobre o crescimento, absorção e distribuição de sódio, cloro e macronutrientes em plântulas de maracujazeiro-amarelo/ Influence of NaCl salinity on uptake and distribution of sodium, chloride and macronutrients in yellow passion fruit seedlings

Cruz, Jailson Lopes; Pelacani, Claudinéia Regina; Coelho, Eugênio Ferreira; Caldas, Ranulfo Correa; Almeida, Adriana Queiroz de; Queiroz, Jurema Rosa de
2006-01-01

Resumo em português A presença de sódio (Na) e de cloro (Cl) no substrato tem ocasionado redução no crescimento dos vegetais, em virtude desses íons causarem, entre outros efeitos negativos, mudanças na capacidade das plantas em absorver, transportar e utilizar alguns dos nutrientes. Assim, o objetivo do presente trabalho foi o de avaliar a influência da salinidade sobre o crescimento e a absorção e distribuição do Na e Cl e dos macronutrientes em plântulas de Maracujazeiro-amare (mais) lo, durante 50 dias de crescimento sob condições salinas, em vasos com capacidade para 2,2 dm³. Foram utilizados três níveis de NaCl (0, 50 e 100 m mol L-1). Observou-se que a altura, o número de folhas, a área foliar e a massa seca de todas as partes da planta foram significativamente reduzidas pela salinidade. A concentração dos íons Na e Cl aumentaram com o acréscimo da salinidade no meio de cultivo, porém, foram parcialmente retidos na raiz, no caso do Cl, e nas folhas mais velhas, no caso do Na. As concentrações de nitrogênio (N), fósforo (P) e cálcio (Ca) não foram afetadas pela salinidade. As concentrações de potássio (K), ao contrário, decresceram em todas as partes da planta, enquanto as do enxofre (S) foi reduzida apenas nas raízes. Dada a pequena redução nas características de crescimento conclui-se que o Maracujazeiro-amarelo é uma espécie moderadamente tolerante ao estresse salino. Resumo em inglês The presence of sodium (Na) and chloride (Cl) in growth medium have leaded to crop growth due to because of negative effects of these ions such as changes in plant capacity of uptake, transport and use of essential nutrients. The objective of this work was to evaluate the influence of salinity on growth, uptake and transport of Na, Cl and macronutrients in yellow passion fruit plants. Three levels of NaCl (0, 50 and 100 m mol L-1) were tested. Experiment was finished afte (mais) r 50 days of growing in 2.2 dm³ pots. It was noticed that height, leaf number, leaf area and dry mass of all parts of the plant were reduced by salinity. The concentration of Na and Cl ions increased with the increasing of salinity. However, ions were retained partially in roots (Cl) and in older leaves (Na). Concentration of nitrogen (N), phosphorous (P) and calcium (Ca) were not affected by salinity. Actually, concentration of potassium (K) was reduced in all parts of the plant while sulfur (S) was reduced only in roots. Based upon the short reduction on growth characteristics, it was concluded thatyellow passion fruit crop has a moderated tolerance to saline stress.

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Deslocamento miscível de nitrato e fosfato proveniente de água residuária da suinocultura em colunas de solo/ Miscible displacement of nitrate and phosphate from swine wastewater in soil columns

Anami, Marcelo H.; Sampaio, Silvio C.; Suszek, Morgana; Gomes, Simone D.; Queiroz, Manoel M. F. de
2008-02-01

Resumo em português A fertirrigação com águas residuárias da suinocultura vem sendo muito difundida no País, principalmente na região sul do Brasil, entretanto, o alto potencial poluidor dos dejetos pode tornar-se uma ameaça de contaminação de solos e águas superficiais e subterrâneas se utilizados em quantidades excessivas. Neste trabalho o objetivo principal foi avaliar o processo de lixiviação de íons nitrato e fosfato em colunas de solo, obtendo-se os coeficientes de disper (mais) são hidrodinâmico e o fator de retardamento para a determinação do potencial de contaminação dos lençóis de água subterrâneos. Verificou-se, ainda, o efeito da aplicação de águas residuárias da suinocultura tratada com reatores anaeróbios sobre as propriedades físico-químicas do solo, cujos resultados indicaram que o potencial de contaminação dos lençóis de água subterrâneos pelo íon nitrato é elevado, ao contrário do que ocorre com o íon fosfato, que apresentou baixo potencial de contaminação em função da sua alta reatividade. Resumo em inglês Fertigation with wastewater from swine is very much used, mainly in the southern region of Brazil. However, the high polluting potential of these wastewaters represents a threat of soil contamination of surface and underground waters if used in excessive amounts. The objective of this work was to evaluate the leaching process of nitrate and phosphate ions in soil columns, getting the hydrodynamic dispersion coefficient and factor of retardation and potential of contaminat (mais) ion of underground water. The effect of wastewater application on physical and chemical properties of the soil was verified. The results showed that the potential for contamination of underground water by nitrate ions is high, in contrast to what occurs with phosphate ions that presented low potential of contamination due to their high reactivity.

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Composição de ácidos graxos em raízes de sorgo sob estresse de alumínio/ Fatty acid composition of sorghum roots under aluminum stress

Peixoto, Paulo Henrique Pereira; Cambraia, José
2009-01-01

Resumo em português Este trabalho teve por objetivo determinar a influência do Al sobre a composição de ácidos graxos em raízes de duas cultivares de sorgo [Sorghum bicolor (L.) Moench] com tolerância diferencial ao Al. Após exposição das plantas ao Al, raízes foram coletadas, os lipídios extraídos e determinada sua composição em ácidos graxos. O palmítico e, especialmente, o linoléico foram os principais ácidos graxos identificados nos extratos lipídicos de raízes das du (mais) as cultivares, independentemente da presença do Al. Nas plantas tratadas com Al, os teores dos ácidos esteárico e oléico aumentaram apenas na cultivar tolerante, mas os teores do ácido linolênico reduziram nas duas cultivares. Essas alterações na composição de ácidos graxos, o índice de ligações duplas para ácidos graxos contendo 18 carbonos (ILD C18) e as relações ácidos graxos saturados/ácidos graxos insaturados (AGI/AGS) e ácido linoléico/ácido palmítico (18:2/16:0) sugerem que ocorre redução na fluidez dos lipídios da cultivar tolerante, porém aumento na sensível. A redução na fluidez dos lipídios na cultivar tolerante, comparativamente à da sensível sugere ter a cultivar tolerante maior capacidade de reter íons e metabólitos essenciais e, ou limitar a entrada do Al em suas raízes. Resumo em inglês The objective of this work was to determine Al effect on fatty acid composition of roots from two sorghum (Sorghum bicolor (L.) Moench) cultivars with differential tolerance to aluminum. After exposure to Al, roots were collected, lipids extracted and the fatty acid composition determined. Palmitic and, especially, linoleic acid were the major fatty acids identified in the root lipid extracts of both cultivars, regardless of the presence of aluminum. Stearic and oleic aci (mais) ds contents increase only in the tolerant cultivar, while linolenic acid decreased in both cultivars after Al treatment. These changes in fatty acid composition, as well as in the C18-fatty acid double bound index (DBI C18) and in the ratios of unsaturated fatty acid/saturated fatty acid (UFA/SFA) and linoleic acid/palmitic acid (18:2/16:0) indicated of a reduction of the lipid fluidity of the tolerant cultivar, but an increase in the sensitive one. The observed reduction in lipid fluidity in the tolerant relative to the sensitive cultivar suggests of a better capacity of the tolerant cultivar to retain essential ions and metabolites and/or to limit the entry of toxic Al ions into roots.

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Utilização de zeólita preparada a partir de cinza residuária de carvão como adsorvedor de metais em água/ Use of zeolite from coal bottom ash as adsorbent of metals from water

Fungaro, Denise Alves; Silva, Magali Guilherme da
2002-12-01

Resumo em inglês Coal ashes produced in coal-fired power plant could be converted into zeolites and can be used as low-cost adsorbents for the treatment of effluents contaminated with high levels of toxic metals. The capacity of synthetic zeolites for the removal of cadmium, zinc and copper ions from aqueous solutions has been investigated under different operating conditions. Zeolite from bottom chimney showed higher removal efficiency for metals ions than zeolite from feed hopper and mi (mais) xing mill. The results indicated that the treated bottom ash could be applied in environmental technology as an immobilizer of pollutants.

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Uma visão da química bioinorgânica medicinal/ Medicinal bioinorganic chemistry

Benite, Anna Maria Canavarro; Machado, Sérgio de Paula; Barreiro, Eliezer J.
2007-01-01

Resumo em inglês Metals play a vital role in human and plant physiology and important research is directed towards exploring the interrelated mechanisms that govern their interactions with biomolecules. Bioinorganic medicinal chemistry studies the functions, processing, storage and applications of metal ions and their complexes in biological systems. This paper presents a brief discussion about on interactions of metals with biomolecules that determine their intracellular accumulation, wh (mais) ere metal ions may fulfill essential functions in cellular metabolism or, in certain cases, exert toxic effects towards cells.

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Um experimento-charada usando data-show e resinas de troca iônica/ A quiz-experiment using data-show and ion exchange resins

Osorio, Viktoria Klara Lakatos; Kuya, Miuaco Kawashita; Maia, Alessandra de Souza; Oliveira, Wanda de
2003-12-01

Resumo em inglês A demonstractive experiment was proposed in order to verify students' habilities in recognizing the presence and nature of ions in solutions, before and after their passage through ion-exchange columns. The students have no previous contact with ion-exchange resins, so they must deduce how they work and explain the experimental facts. The performance of classes, at different stages of learning, is compared and discussed.

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Um equipamento de eletroforese capilar com detecção condutométrica construído em laboratório/ A laboratory-made capillary electrophoresis equipment with conductometric detection

Böckel, Wolmir J.; Martini, Emilse M. A.; Samios, Dimitrios; Piatnicki, Clarisse M. S.
2005-12-01

Resumo em inglês A new construction of a capillary electrophoresis instrument with a universal conductivity detector (oscillometric detector) is described. The performance of the electrophoresis equipment was evaluated through the separation and detection of inorganic anions and cations in aqueous solutions. The results reproduced those found in the literature for the investigated probe ions, showing an efficient separation and good repeatability.

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SSPBE: um programa para solução numérica da equação de Poisson-Boltzmann em simetria esférica com modelo de adsorção/ SSPBE: a program for numerical solution of the spherically symmetric Poisson-Boltzmann equation along with a site binding model

Dias, Luís Gustavo; Chaimovich, Hernan; Politi, Mário José
2002-11-01

Resumo em inglês A Fortran77 program, SSPBE, designed to solve the spherically symmetric Poisson-Boltzmann equation using cell model for ionic macromolecular aggregates or macroions is presented. The program includes an adsorption model for ions at the aggregate surface. The working algorithm solves the Poisson-Boltzmann equation in the integral representation using the Picard iteration method. Input parameters are introduced via an ASCII file, sspbe.txt. Output files yield the radial dis (mais) tances versus mean field potentials and average molar ion concentrations, the molar concentration of ions at the cell boundary, the self-consistent degree of ion adsorption from the surface and other related data. Ion binding to ionic, zwitterionic and reverse micelles are presented as representative examples of the applications of the SSPBE program.

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Remoção de metais de solução aquosa usando bagaço de caju/ Metal removal from aqueous solution using cashew bagasse

Moreira, Sarah A.; Sousa, Francisco W.; Oliveira, André G.; Nascimento, Ronaldo F.; Brito, Edy Sousa de
2009-01-01

Resumo em inglês The metal ions removal on cashew bagasse, a low-cost material, has been studied by batch adsorption. The parameters chemical treatment, particle size, biosorbent concentration, and initial pH were studied. In this study the maximum ions removal was obtained on the cashew bagasse treated with 0.1 mol/L NaOH/3 h, at optimum particle size (20-59 mesh), biosorbent concentration (50 g/L) and initial solution pH 5. The kinetic study indicated that the adsorption metal follows p (mais) seudo-second order model for a multielementary system and equilibrium time was achieved in 60 min for all metal ions.

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Refletindo sobre o caso celobar®/ Reflecting on the celobar® case

Tubino, Matthieu; Simoni, José de Alencar
2007-04-01

Resumo em inglês By mid 2003, the Brazilian people accompanied astonished, in the press, the news about the death of more than 20 persons due to ingestion of a pharmaceutical product containing a suspension of barium sulfate (Celobar®) commonly used as a radiological contrast. Analysis of the product indicated the presence of barium carbonate (about 13% weight/weight) which reacts easily with the hydrochloric acid in the stomach liberating barium ions, a severe poison. In this article, we briefly discuss the possible economic, personal and technical causes that led to this disaster.

Scientific Electronic Library Online (Portuguese)

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Reciclagem do crômio de resíduos químicos provenientes da determinação de carbono oxidável em fertilizantes orgânicos/ Recycling of chromium in chemical waste from oxidizable carbon determination in organic fertilizer

Machado, Jeane M. C; Oliveira, Lenita M. C. P. E; Kamogawa, Marcos Y
2011-01-01

Resumo em inglês This work proposes a separation, recovery and reuse procedure of chemical residues with chromium. This residue was generated by the determination of oxidizable carbon in organic fertilizers samples. The Cr(VI) of the residue was reduced with ethanol and precipitated with NaOH. The Cr(OH)3 precipitate was separated and oxidized to dichromate ions with hydrogen peroxide. This solution was used another time in organic carbon determination. The uses of recycled dichromate sol (mais) ution were appropriated in four successive recycling. The accuracy was proven using potassium hydrogen phthalate and ten organic fertilizer samples. The organic carbon results, determined with recycled solutions, were similar the conventional solution.

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Química de complexos de (etilenodiaminatetraacetato)rutenato(III/II)/ Ruthenium complexes containing ethylenediaminetetraacetate

Rein, Francisca N.; Rocha, Reginaldo C.; Toma, Henrique E.
2004-02-01

Resumo em inglês This paper provides a survey of general aspects involved in the coordination chemistry of low-valent (mainly +III,+II), low-spin (d p5,d p6) ruthenium ions with ethylenediamine-N,N,N',N'-tetraacetate (edta) and their substituted derivatives. The topics covered herein include structure, reactivity, kinetics, thermodynamics, electrochemistry and spectroscopy. The contributions from either our research group or the literature over the last three decades are focused in this review.

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Química atmosférica do enxofre (IV): emissões, reações em fase aquosa e impacto ambiental/ Atmospheric chemistry of sulfur (IV): emissions, aqueous phase reactions and environmental effects

Martins, Cláudia Rocha; Andrade, Jailson Bittencourt de
2002-05-01

Resumo em inglês The oxidation process of sulfur(IV) species by oxygen, ozone and nitrogen oxides, catalysed by trace metal ions, can play an important role in atmospheric chemistry processes like acid rain, visibility degradation and health hazard. An overview of the more relevant investigations on emissions sources, aqueous phase conversion process and environmental impact is presented.

Scientific Electronic Library Online (Portuguese)

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Propriedades fotofísicas de Eu3+ e Tb3+ imobilizados em sílica gel funcionalizada com beta-Dicetonas/ Photophysical properties of Eu3+ and Tb3+ supported on silica gel functionalized with beta-diketones

Nassar, Eduardo José; Serra, Osvaldo Antonio
2000-02-01

Resumo em inglês Synthetic procedures, characterization and luminescent properties of Eu3+ and Tb3+ ions supported on silica gel functionalized with beta-diketones are presented. The functionalization with propyl benzoyltrifluoroacetone (BPG), dibenzoylmethane (DBM) and hexafluoroacetone (HPG), leads to new luminescent materials which photophysical properties depend on the group substituent in the beta-diketone. These systems were evaluated in terms of luminescence and lifetime of the Eu3 (mais) + and Tb3+ ions. Silica functionalization was confirmed by TGA and Elemental Analysis. The sample contents of ions were from 0,2 to 0,3 % (w/w).

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Oxocarbonos, pseudo-oxocarbonos e esquaraínas/ Oxocarbons, pseudo-oxocarbons and squaraines

Oliveira, Vanessa E. de; Diniz, Renata; Oliveira, Luiz Fernando C. de
2009-01-01

Resumo em inglês Oxocarbons ions are cyclic compounds presenting unusual electronic and vibrational properties. These molecules anions possess a high symmetry and degree of electronic delocalization, characteristics that have been discussed in several structural and spectroscopic investigations. Compounds in which one or more of the carbonyl oxygen atoms are replaced by other atoms or groups are called pseudo-oxocarbons. Compounds formed by substitution of the carbonyl groups by nitrogen (mais) groups former a new class named squaraines. Specificity the dicyanomethylene groups are interesting because of the possibility of further extension of the electronic delocalization and a new coordination site. These molecules also present interesting coordination properties which make these systems potentially useful in crystal engineering research.

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O ressurgimento da química de benzino com sililaril triflatos no contexto das reações de inserção em ligações sigma/ The benzyne chemistry revival with silylaryl triflates in the context of insertion reactions into sigma bonds

Gallo, Rafael D. C.; Rezende, Hellenicy V.; Muzzi, Rozanna M.; Raminelli, Cristiano
2009-01-01

Resumo em inglês In this paper we gathered articles concerning insertion reactions of arynes, exclusively generated from 2-(trimethylsilyl)aryl triflates in the presence of fluoride ions, in substrates bearing nucleophilic and electrophilic portions separated by sigma bonds. Accordingly, we stand out the great importance and versatility of such transformations in the preparation of highly functionalized aromatic systems, which are hardly synthesized in just one step for other methods.

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Mecanismo e aplicações da reação de fenton assistida por compostos fenólicos redutores de ferro/ Mechanism and applications of the fenton reaction assisted by iron-reducing phenolic compounds

Aguiar, André; Ferraz, André; Contreras, David; Rodríguez, Jaime
2007-06-01

Resumo em inglês The mechanism and applications of the Fenton reaction assisted by iron-reducing phenolic compounds (IRPC) is reviewed. The presence of IRPC leads to the formation of a larger number of free radicals. The relationship between the redox potential and the IRPC structure is discussed. The effect of humic substances in the degradation of xenobiotics is also included, since these substances are able to reduce metallic ions. The natural occurrence of Fe3+/H2O2/IRPC in wood biode (mais) gradation processes, as well as their application is also discussed. The review concludes with the advantages of the Fe3+/H2O2/IRPC systems and some considerations for further process optimization and their applications at industrial levels.

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Integração de técnicas analíticas e proposta de experimentos para cursos de graduação em análise instrumental: uso de espectrômetro de absorção atômica para medidas de absorção molecular/ Integration of analytical techniques and undergraduate laboratory in instrumental analysis: use of an atomic absorption spectrometer for molecular absorption measurements

Gomes, Marcos S.; Trevizan, Lilian C.; Nóbrega, Joaquim A.; Gouveia, Sandro T.; Rocha, Fábio R. P.
2006-07-01

Resumo em inglês Simple experiments are proposed for measuring molecular absorption of chromate and dichromate ions using an atomic absorption spectrometer. The experiments can help undergraduate students in instrumental analysis courses understand important aspects involving conceptual and instrumental similarities and differences between frequently used analytical techniques. Hollow cathode lamps were selected with wavelengths in the region of molecular absorption of chromate and dichro (mais) mate. Calibration curves were obtained and the linear dynamic range was evaluated. Results were compared with those obtained in a molecular absorption spectrometer. The molar absorptivities obtained were also compared.

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Hidrogenação eletrocatalítica de substratos orgânicos: estudo da eficiência dos metais nobres níquel, paládio e platina usando eletrodos modificados/ Electrocatalytic hydrogenation of organic substrates: study of the efficiency of the nickel, paladium and platinum noble metals using modified electrodes

Pontólio, José Olavo S.; Purgato, Fabiana L. S.; Romero, José R.
2004-08-01

Resumo em inglês Nickel, palladium and platinum micro-crystals were dispersed in films covering a vitreous carbon plate electrode by ion exchange followed by electroreduction of their ions. These modified electrodes were used in the electrocatalytic hydrogenation of several substrates of different classes and their efficiency is reported. A comparison among them was performed based on the structural characteristics of the metals. A modified electrode containing platinum showed to be more efficient than a palladium modified electrode and the one of nickel was the less efficient.

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Extração de Al(III), Cr(III) e Fe(III) de meio etanólico usando o xerogel anilinapropilsílica/ Extraction of Al(III), Cr(III) and Fe(III) from ethanolic medium by anilinepropylsilica xerogel

Pavan, Flávio A.; Costa, Tania M. H.; Benvenutti, Edilson V.; Jacques, Rosângela A.; Córdova, Manuela C.
2004-10-01

Resumo em inglês In this study, the preparation of the xerogel anilinepropylsilica is reported. The ability of the xerogel for extracting Al(III), Cr(III) and Fe(III) from ethanol was investigated at 25 ºC. The xerogel adsorption capacities were obtained from the adsorption isotherms by using the batch method. Flame atomic absorption spectrometry (FAAS) was used to estimate the concentration of metal ions in solution. The adsorption affinity follows the series Cr(III) > Fe(III) > Al(III) and the maximum adsorption capacities of the metal ions were 0.61, 0.52 and 0.43 mmol g-1, respectively.

Scientific Electronic Library Online (Portuguese)

79

Estudo do equilíbrio e cinética da biossorção do pb2+ por saccharomyces cerevisiae/ Equilibrium and kinetic study of pb2+ biosorption by saccharomyces cerevisiae

Ferreira, Joelma Morais; Silva, Flávio Luiz Honorato da; Alsina, Odelsia Leonor Sanchez; Oliveira, Líbia de Sousa Conrado; Cavalcanti, Eliane Bezerra; Gomes, Wolia Costa
2007-10-01

Resumo em inglês The biosorption, based on the use of biomass for removal of ions is distinguished as an innovative and promising technology when compared with the traditional methods. In this context, the aim of the present work is to use Saccharomyces cerevisiae as biosorbent for the retention of Pb2+ metal ions. Factorial design was used for evaluation of the process. The observed equilibrium data were well described by Langmuir and Freundlich adsorption isotherms. The maximum adsorpti (mais) on capacity was 1486.88 mg/g. The results indicated that Saccharomyces cerevisiae is suitable for biosorption of Pb2+ metal ions.

Scientific Electronic Library Online (Portuguese)

80

Estudo das interações entre o complexo polieletrolítico trimetilquitosana/carboximetilcelulose e Cu+2, ácido húmico e atrazina em solução aquosa/ Study of the interactions between the polyelectrolyte complex trimethylchitosan/carboxymethylcellulose and Cu+2, humic acid and atrazine in aqueous solution

Campana-Filho, Sergio P.; Britto, Douglas de
2009-01-01

Resumo em inglês The polyelectrolyte complex (PEC) resulting from the reaction of sodium carboxymethylcellulose (CMC) and N,N,N-trimethylchitosan hydrochloride (TMQ) was prepared and then characterized by infrared spectroscopy and energy dispersive X rays analysis. The interactions involving the PEC and Cu2+ ions, humic acid and atrazine in aqueous medium were studied. From the adsorption isotherms the maximum amount adsorbed (Xmax) was determined as 61 mg Cu2+/g PEC, 171 mg humic acid/g (mais) PEC and 5 mg atrazine/g PEC. The results show that the CMC/TMQ complex has a high affinity for the studied species, indicating its potential application to remove them from aqueous media.

Scientific Electronic Library Online (Portuguese)

81

Estudo da oxidação dos sulfetos sintéticos molibdenita (MoS2) e covelita (CuS) por Acidithiobacillus ferrooxidans via respirometria celular/ Oxidation study of the synthetic sulfides molybdenite (MoS2) and covellite (CuS) by Acidithiobacillus ferrooxidans using respirometric experiments

Francisco Junior, Wilmo E.; Bevilaqua, Denise; Garcia Júnior, Oswaldo
2009-01-01

Resumo em inglês This paper analyses the oxidation of covellite and molybdenite by Acidithiobacillus ferrooxidans strain LR using respirometric experiments. The results showed that both sulfides were oxidized by A. ferrooxidans, however, the covellite oxidation was much higher than molybdenite. Regarding the kinetic oxidation, the findings revealed that just molybdenite oxidation followed the classical Michaelis-Menten kinetic. It is probably associated with the pathway which these sulfid (mais) es react to chemistry-bacterial attack, what is influenced by its electronic structures. Besides, experiments conducted in the presence of Fe3+ did not indicate alterations in molybdenite oxidation. Thus, ferric ions seem not to be essential to the sulfide oxidations.

Scientific Electronic Library Online (Portuguese)

82

Emprego de reagente em suspensão em sistema de injeção em fluxo: determinação espectrofotométrica de sulfato em águas naturais/ Use of reagent in suspension in flow injection analysis: spectrophotometric determination of sulphate in natural water

Crnkovic, Paula Manoel; Jacintho, Antonio Octávio
2002-05-01

Resumo em inglês This paper presents an automatic procedure employing a reagent in the form of a slurry in a flow-injection system. The feasibility of the proposal is demonstrated by sulphate determination in water using the Barium Chloranilate method, which is based on the precipitation of barium sulphate. The release of a stoichiometric amount of highly colored chloranilic ions is monitored at 528 nm. The reaction is carried out in alcoholic medium in order to reduce the solubility of t (mais) he reagent. A considerable improvement in the sensitivity is attained by adding ferric ions to the released chloranilic ions. An on-line filtration step to separate the excess reagent from the released chloranilic ions was necessary. In addition, a column containing a cation exchange resin was included in the manifold to remove potentially interfering ions. The proposed procedure is suitable for 30 determinations per hour and the relative standard deviation is less than 2%. The analytical curve is linear between 0.0 and 40 mg L-1 and the determination limit is about 2.0 mg L-1SO4(2-). Accuracy was confirmed by running several samples already analysed by a standard turbidimetric procedure.

Scientific Electronic Library Online (Portuguese)

83

Determinação de nitrito em águas utilizando extrato de flores/ Determination of nitrite in water using a flower extract

Ramos, Luiz Antônio; Cavalheiro, Carla Cristina Schmitt; Cavalheiro, Éder Tadeu Gomes
2006-10-01

Resumo em inglês Aspects of visible spectrophotometry can be presented to students using simple experiments in which the color of the crude extract of Macroptilium lathyroides (L.) Urb. is bleached in the presence of nitrite ions in acidic medium. The dependence of the absorption intensity with time, the reaction completeness and the Beer law can be demonstrated. Quantitative results for mineral water samples "contaminated" with nitrite ions were obtained from a method based on the Griess (mais) reaction and a procedure based on the bleaching reaction between the crude extract and NO2- ions. Both the Griess and the bleaching reactions were found to be time dependent. Recoveries of about 100 - 104% were obtained with these procedures. The use of natural dyes attracted students' interest enhancing the teaching process. Experiments performed by the teaching staff suggested that the proposed methodology can be performed in a 4 h class, with relative errors ranging from 0.19 to 1.86% in relation to the Griess method.

Scientific Electronic Library Online (Portuguese)

84

Determinação de bromato em melhoradores de farinha por cromatografia de troca iônica com detecção espectrofotométrica/ Bromate determination in flour improvers by ion exchange chromatography with spectrophotometric detection

Dallago, Rogério Marcos; Nascimento Filho, Irajá do; Zanella, Renato; Maroneze, Aline Machado
2005-08-01

Resumo em inglês KBrO3 is registered by the FAO/OMS as a genotoxic and carcinogenic compound. In spite of this, KBrO3 is still employed by Brazilian bakeries. Nowadays ion exchange chromatography (IEC) is the most rapid and trustful method for BrO3- analysis. When at high concentrations, chloride ions can interfere in the BrO3- analysis, if the detection is performed by electrical conductivity. On the other hand, spectrophotometric detection, presented here is based on the absorption of B (mais) rO3- in the ultraviolet region (210 - 230 nm) where the absortion of chloride ions is very low, thus making possible the qualitative and quantitative analysis of BrO3- in flour improver samples.

Scientific Electronic Library Online (Portuguese)

85

Determinação condutométrica de cloridrato de metformina em formulações farmacêuticas empregando nitrato de prata como titulante/ Conductometric determination of metformin hydrochloride in pharmaceutical formulations using silver nitrate as titrant

Sartori, Elen Romão; Suarez, Willian Toito; Fatibello-Filho, Orlando
2009-01-01

Resumo em inglês A simple, precise, rapid and low-cost conductometric titration method for the determination of metformin hydrochloride (MET) in pharmaceuticals using silver nitrate as titrant is proposed. The method was based on the chemical reaction between the chloride of metformin hydrochloride molecule and Ag(I) ions, yielding the precipitate AgCl(s). The method was applied for MET determination in three pharmaceuticals and the obtained results with proposed method were in close agre (mais) ement with those results obtained using an official method of the British Pharmacopoeia, at a 95% confidence level.

Scientific Electronic Library Online (Portuguese)

86

Determinação condutométrica de captopril em formulações farmacêuticas utilizando sulfato de cobre(II) como titulante/ Conductometric determination of captopril in pharmaceutical formulations using copper(II) sulphate as titrant

Lourenção, Bruna Cláudia; Marcolino-Junior, Luiz Humberto; Fatibello-Filho, Orlando
2008-01-01

Resumo em inglês A simple and rapid conductometric method for captopril determination using copper(II) sulphate solution as titrant was developed. The method was based on the chemical reaction between captopril and Cu(II) ions yielding a precipitate. The conductance of the solution was monitored as a function of the added volume of titrant. The method was applied with success for captopril determination in three pharmaceutical formulations. The relative standard deviation for six successi (mais) ve measurements was smaller than 0.5%. Recovery values from three samples, ranging from 97.7 to 103%, were obtained.

Scientific Electronic Library Online (Portuguese)

88

Degradação eletroquímica do cloranfenicol em reator de fluxo/ Electrochemical degradation of the chloramphenicol at flow reactor

Rezende, Luis Gustavo P.; Prado, Vânia M. do; Rocha, Robson S.; Beati, André A. G. F.; Sotomayor, Maria Del Pilar T.; Lanza, Marcos R. V.
2010-01-01

Resumo em inglês This paper reports a study of electrochemical degradation of the chloramphenicol antibiotic in aqueous medium using a flow-by reactor with DSA® anode. The process efficiency was monitored by chloramphenicol concentration analysis with liquid chromatography (HPLC) during the experiments. Analysis of Total Organic Carbon (TOC) was performed to estimate the degradation degree and Ion Chromatography (IC) was performed to determinate inorganic ions formed during the eletroche (mais) mical degradation process. In electrochemical flow-by reactor, 52% of chloramphenicol was degraded, with 12% TOC reduction. IC analysis showed the production of chloride ions (25 mg L-1), nitrate ions (6 mg L-1) and nitrite ions (4.5 mg L-1).

Scientific Electronic Library Online (Portuguese)

89

Degradação de corantes reativos por processo foto-fenton envolvendo o uso de peneira molecular 4A modificada com Fe3+/ Degradation of reactive dyes by photo-fenton process using Fe3+ immobilized in molecular sieve 4A

Ignachewski, Franciély; Fujiwara, Sérgio Toshio; Cótica, Luiz Fernando; Carneiro, Livia Melo; Tauchert, Elias; Peralta-Zamora, Patricio
2010-01-01

Resumo em inglês In this work the preparation and characterization of a supported catalyst intended for degradation of reactive dyes by Fenton-like processes is described. The photocatalyst was prepared by immobilization of Fe3+ into the molecular sieve (4A type) surface and characterized by x-ray diffractometry and infrared, Mössbauer and EPR spectroscopy. The solid containing 0.94% (w/w) of ferric ions was used in degradation studies of aqueous reactive-dyes samples with really promiss (mais) ory results. Generally, Vis-assisted photochemical processes leads to almost total decolorization of all tested dyes at reaction times lower than 30 min. It was also observed that the iron-molecular sieve matrix can be reused.

Scientific Electronic Library Online (Portuguese)

90

Complexos metálicos com o herbicida glifosato: revisão/ Metallic complexes with glyphosate: a review

Coutinho, Cláudia F. B.; Mazo, Luiz Henrique
2005-12-01

Resumo em inglês We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

Scientific Electronic Library Online (Portuguese)

91

Cerâmicas bioativas: estado da arte/ Bioactive ceramics: state of the arts

Andrade, Ângela Leão; Domingues, Rosana Zacarias
2006-02-01

Resumo em inglês Bioactive glasses undergo corrosion with leaching of alkaline ions when exposed to body fluids. This results in the spontaneous formation of a layer of hydroxyapatite (HA), the mineral component of natural bone, which in turn can induce bone growth in vivo. This paper describes the different types of bioactive glasses, the characterization methods currently used, and the main factors that influence their bioactivity. Nucleation and crystallization, the main mechanisms inv (mais) olved in the formation of hydroxyapatite, Ca10(PO4)6(OH)2, are discussed as a function of the chemical composition and the reactivity of the surface of the material. Finally, promising applications are considered.

Scientific Electronic Library Online (Portuguese)

92

Características ópticas e morfológicas de nanoestruturas de ouro/ Optical and morphological characteristics of gold nanostructures

Pereira, Francisco Claudece; Zanoni, Maria Valnice Boldrin; Moretto, Ligia Maria; Ugo, Paolo
2007-01-01

Resumo em inglês The present study describes a new procedure to obtain gold nanoparticles, directly in the pores of polycarbonate membranes commonly used in ultrafiltration. The dimensions of the particles may be controlled through the reduction time of the ions in the channels of the harbor matrix. The dissolution of the metallized polymer enables an investigation of the optical and morphologic properties of these elements.

Scientific Electronic Library Online (Portuguese)

93

Avaliação do efeito da concentração de carbonato na eletrodeposição de cobre sobre discos de aço-carbono/ Evaluation of the effect of carbonate concentration in the copper electrodeposition on mild steel blankets

Silva, Angélica Inês Ferreira da; Afonso, Júlio Carlos; Sobral, Luis Gonzaga Santos
2008-01-01

Resumo em inglês Mild steel blankets were covered with electrolytic copper thin layer, from cyanide bath, being evaluated the influence of the carbonate concentration in the physiochemical properties of those deposits. The cell voltage decreased as the current intensity decreased, but the adherence of the deposit was not enhanced, showing that the increment of carbonate concentration causes substantial problems. Chemical solubilization reactions of air-bearing carbon dioxide and oxidation (mais) of free cyanide ions through dissolved oxygen evolved in the anodic processes contribute to the copper plating to occur in an inefficient way. The best optimal conditions require a carbonate concentration below 50 g L-1.

Scientific Electronic Library Online (Portuguese)

94

Avaliação da liberação de NH4NO3 ocluido em zeólita 4A a partir de soluções salinas/ Assessment of release of NH4NO3 occluded zeolite 4A in solutions from salinas

Andrade, Jardel Cavalcante Rolim de Almeida; Loiola, Adonay Rodrigues; Silva, Lindomar Roberto Damasceno da; Romero, Ricardo Espíndola
2010-01-01

Resumo em inglês The zeolite 4A was used to evaluate the thermo kinetics parameters of NH4+ and NO3- ions occluded in its structure. The Osawa method for activation energy calculation was used to evaluate its thermal stability, and the results shown that the ion species interact differently depending on the zeolite pores, which determines the controlled release by its structure.

Scientific Electronic Library Online (Portuguese)

95

Aspectos estruturais relacionados ao processo de troca iônica no niobato lamelar K4Nb6O17/ Structural aspects related to the ion exchange process in layered niobate K4Nb6O17

Bizeto, Marcos A.; Christino, Fernando P.; Tavares, Marina F. M.; Constantino, Vera R. L.
2006-12-01

Resumo em inglês The niobate with formula K4Nb6O17 has a layered structure formed by stacked negative sheets and exchangeable cations in the interlayer region. In this study we discuss some structural aspects related to the ion exchange in layered hexaniobate based on X-ray diffractometry and vibrational Raman spectroscopy data. Hexaniobate has two distinct interlayer regions and the potassium ions of one interlayer in particular are preferably exchanged by other cations, leading to an interstratified material.

Scientific Electronic Library Online (Portuguese)

96

Aplicação e modificação química da sílica gel obtida de areia/ Aplication and chemical modification of silica-gel obtained from sand

Prado, Alexandre G. S.; Faria, Elaine A.; Padilha, Pedro M.
2005-06-01

Resumo em inglês The silica gel was obtained from sand and its surface was modified with POCl3 to produce Si-Cl bonds on the silica surface. Ethylenediamine was covalently bonded onto the chlorinated silica surface. The adsorption of the chlorides of divalent cobalt, nickel and copper was qualitatively studied to show that the bonding of ethylenediamine onto the silica gel surface produces a solid base capable of chelating metal ions from solution. The experiments illustrate the extractio (mais) n of silica gel, its reactivity, the development of modified surfaces and its application in removing metal ions from water and are deigned for undergraduate inorganic chemistry laboratories.

Scientific Electronic Library Online (Portuguese)

97

Aplicação de zeólitas sintéticas como coadjuvante em formulação detergente/ Application of synthetic zeolites as builder in detergent formulation

Sutili, Felipe K.; Miotto, Naiara; Rigoti, Eduardo; Pergher, Sibele B. C.; Penha, Fábio G.
2009-01-01

Resumo em inglês The study consists is the application of zeolites NaX, NaY and A as builder in detergent formulations to eliminate the hardness of water. Therefore, the adsorption of ions Ca+2 and Mg+2 were evaluated, and the effect of the cleaning action of the surfactant sodium dodecil sulfate (SDS) through tests of detergency. The experiments were conducted in bath system (with shaking) and quantification of metals was performed by atomic absorption spectrometry. Zeolite A showed the (mais) best results for adsorption of Ca++ and Mg++ with retention rates of around 90 and 70% respectively and acted positively on the action of cleaning the surfactant SDS.

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98

Aplicação de adsorção para remover amônia de efluentes suinícolas pré-tratados/ Adsorption applied to the removal of ammonia from pre-treated piggery wastewater

Higarashi, Martha Mayumi; Kunz, Airton; Mattei, Rosemari Martini
2008-01-01

Resumo em inglês The aim of this work is to evaluate the use of natural zeolites to remove the NH4+ that remains in effluents from swine facilities which were submitted to physico-chemical and biological treatments. Experiments were made in batch made adding 5% (w/w) of adsorbent (0.6-1.3 and 3.0-8.0 mm) to synthetic and real swine facilities effluents. The results show that ammonium removal is influenced by adsorbent particle size and the presence of other ions in the effluent. The adsor (mais) ption equilibrium was described by Langmuir as well as Freundlich isotherms and the kinetic data fitted well a pseudo-second order model.

Scientific Electronic Library Online (Portuguese)

99

Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas/ Application of computational quantum chemistry to chemical processes involved in mass spectrometry

Vessecchi, Ricardo; Galembeck, Sérgio E.; Lopes, Norberto P.; Nascimento, Paulo G. B. D.; Crotti, Antônio E. M.
2008-01-01

Resumo em inglês The field of application of mass spectrometry (MS) has increased considerably due to the development of ionization techniques. Other factors that have stimulated the use of MS are the tandem mass spectrometry (MS/MS) and sequential mass spectrometry (MSn) techniques. However, the interpretation of the MS/MS and MSn data may lead to speculative conclusions. Thus, various quantum chemical methods have been applied for obtaining high quality thermochemical data in gas phase. (mais) In this review, we show some applications of computational quantum chemistry to understand the formation and fragmentation of gaseous ions of organic compounds in a MS analysis.

Scientific Electronic Library Online (Portuguese)

100

Adsorção de zinco e cádmio em colunas de turfa/ Adsorption of zinc and cadmium on peat columns

Petroni, Sérgio Luis Graciano; Pires, Maria Aparecida Faustino; Munita, Casimiro Sepúlveda
2000-08-01

Resumo em inglês The aim of this work was to evaluate the adsorption conditions of zinc and cadmium ions from aqueous solutions using a comercially available peat from Balneário Arroio do Silva, Santa Catarina State, Brazil. Adsorption studies were carried out in column experiments using radiotracers of the studied metals (65Zn and 115Cd). The pH influence and the interference of other ions, such as Na+, Ca2+, Fe3+ and Al3+on the adsorption process were investigated. The results showed t (mais) hat peat columns are able to retain more than 99% of metal ions in solution in a range of pH from 3,7 to 6,5. Ca2+ and Al3+ ions were the main interferent on adsorption of Zn and Cd ions in solution.

Scientific Electronic Library Online (Portuguese)

101

Adsorção de chumbo, cádmio e prata em óxido de nióbio (V) hidratado preparado pelo método da precipitação em solução homogênea/ Cadmium, lead and silver adsorptio in hydrous niobium oxide prepared by homogeneous solution method

Tagliaferro, Gerônimo V; Pereira, Paulo Henrique F; Rodrigues, Liana Álvares; Silva, Maria Lucia Caetano Pinto da
2011-01-01

Resumo em inglês This paper describes the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide. Three heavy metals were selected for this study: cadmium, lead and silver. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacity (Q0) for Pb2 +, Ag+ and Cd2 + was found to be 452.5, 188.68 and 8.85 mg g-1, respectively.

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