Sample records for iron complexes
from WorldWideScience.org

Sample records 1 - 10 shown.



1

Síntese de complexo ferro(II)-nitrogênio: abordagem dos conceitos de reatividade e retro-doação para alunos de graduação em química/ Synthesis of the iron(II)-nitrogen complex: concepts of reactivity and back-bonding for undergraduate chemistry students

Pissetti, Fábio L.; Nonô, Rogério S.; Gushikem, Yoshitaka; Dias, Gilson H. M.
2007-06-01

Resumo em inglês There has been a considerable interest in coordination complexes of molecular nitrogen (N2), partly due to a possible relationship between such complexes and the nitrogen activation process in nature. The present paper describes the synthesis and infrared spectroscopic characterization of an iron-nitrogen derivative with ethylenediamine-N,N,N',N'-tetraacetate (edta) as an experiment for an undergraduate course. The topics covered here include synthesis, reactivity and spectroscopy.

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2

Estudos comparativos entre carvão ativado e resina de troca iônica para adsorção de ouro, cobre e ferro/ Comparative study of activated carbon and ion-exchange resin for the adsorption of gold, copper and iron

Araujo, Danielle Marques; Yoshida, Maria Irene; Stapelfeldt, Frank; Carvalho, Cornélio Freitas; Donnici, Cláudio Luiz; Kastner, Geraldo F.
2009-12-01

Resumo em português O objetivo desse trabalho é a adsorção de cianocomplexos de ouro, cobre e ferro de efluentes que são gerados no processo de beneficiamento do minério de ouro. Para a adsorção foram testadas duas alternativas: resina de troca aniônica com base fraca e o carvão ativado quimicamente modificado. A resina utilizada foi a LEWATIT MP 62 da Bayer S.A. O processo de modificação química do carvão ocorreu em duas etapas: nitração do carvão ativado comercial, seguida (mais) de redução do grupo nitro (NO2) para grupo amino (NH2). Os testes de adsorção revelaram que o carvão ativado modificado apresentou pior eficiência na recuperação de complexos de Au, em relação ao carvão ativado sem tratamento, e que ambos não adsorveram complexos de Cu e Fe. A resina foi a que apresentou melhor recuperação dos complexos de ouro (100%), cobre (99%) e ferro (100%). Resumo em inglês Herein, the adsorption of gold, copper, and iron cyano complexes fromeffluents of t gold ore processing is presented. . For recovery, two alternatives were tested: weak-base ion - exchange resin and chemically modified activated carbon. The resin used was LEWATIT MP 62 from Bayer S.A. Chemical modification was carried out in two steps: nitration of commercial activated carbon followed by the reduction of the nitro group (NO2) to amino group (NH2). Adsorption testes reveal (mais) ed that activated carbon presented poorer efficiency in the recovery of Au complexes in relation to untreated activated carbon, and that they did not adsorb either Cu or Fe complexes. Resin recovered Cu (99%) and Fe(100%) and Au (100%) complexes was the best.

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3

Efeito estrutura da matriz na adsorção de cianocomplexos metálicos em resinas de poliestireno

Riani, Josiane Costa; Carlos, Versiane Albis Leão; Silva, Carlos Antônio da
2004-06-01

Resumo em português O objetivo desse trabalho é a utilização de resinas de troca-iônica, base forte, na adsorção de cianocomplexos metálicos, visando a sua reciclagem. São utilizadas soluções sintéticas que simulam diferentes efluentes da lixiviação do minério de ouro, contendo concentrações de ferro, de zinco e de cobre, variando entre 50 e 500mg/l. São realizados ensaios de adsorção, em batelada, utilizando dois tipos de resinas comerciais: Ionac SR-7 (matriz de poliesti (mais) reno, tripropilamônio quaternário como grupo de troca) e Dowex 1X8 (matriz de poliestireno, trimetilamônio quaternário como grupo de troca). Em ambas resinas houve uma adsorção maior do cianocomplexo de zinco com relação aos outros cianocomplexos metálicos existentes em solução. A ordem do carregamento, nesse caso, foi Zn>Cu>Fe. A resina Dowex 1X8 apresentou um maior carregamento dos cianocomplexos de zinco e de cobre, quando comparados com os carregamentos da outra resina. As diferentes afinidades são discutidas em função das características físico-químicas dos complexos e das estruturas das resinas. Resumo em inglês This work aims the recycling of cyanide applying strong base ion exchange resins for the adsorption of metallic cyanocomplexes. The experiments were carried out with synthetic solutions simulating those found in the cyanidation of gold ores. The solutions are made up of copper, iron and zinc with concentrations raging from 50mg/L to 500mg/L. Batch adsorption experiments were carried out with two commercial strong base resins: Ionac SR-7 (polystyrene, tripropylammonium) an (mais) d Dowex 1X8 (gel type, polystyrene, trimethylammonium). The tripropilammonium resin Ionac SR-7 presents a larger loading of zinc cyanide compared with those of copper and iron. The affinity sequence observed was Zn>Cu>Fe. Dowex 1X8 resin shows the highest uptake of both zinc and copper due to its high exchange capacity. The affinity sequence is similar to that of Ionac SR-7 resin. The different affinities achieved are discussed based on both the physic-chemical features of the complexes and the resin structure.

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4

Variáveis relacionadas à estabilidade de complexos organo-minerais em solos tropicais e subtropicais brasileiros/ Selected soil-variables related to the stability of organo-minerals complexes in tropical and subtropical brazilian soils

Inda Junior, Alberto Vasconcellos; Bayer, Cimélio; Conceição, Paulo Cesar; Boeni, Madalena; Salton, Júlio César; Tonin, Alano Tiago
2007-10-01

Resumo em português A estabilidade de complexos organo-minerais é uma característica importante quanto à química e física de solos tropicais e subtropicais. O objetivo deste estudo foi identificar variáveis relacionadas à estabilidade de complexos organo-minerais, avaliada pela energia de ultra-som necessária para a dispersão total do solo em partículas primárias, em seis solos das regiões Sul e Centro-Oeste do Brasil com textura e mineralogia distintas. A energia de ultra-som ne (mais) cessária para dispersão total dos solos variou de 239 a 2.389J mL-1, sendo diretamente relacionada aos teores de carbono orgânico (R²=0,799, P Resumo em inglês The stability of organo-mineral complexes is an important characteristic related to the soil chemistry and physics of tropical and subtropical soils. This study was aimed at identifing the variables related to the stability of organo-mineral complexes, evaluated by ultrasonic energy necessary to complete soil dispersion, of six soils from South and West-Center regions of Brazil with distint texture and mineralogy. The ultrasonic energy to complete soil dispersion varied f (mais) rom 239 a 2389J mL-1, and was positively related to the soil organic carbon concentrations (R²=0.799, P

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5

Tecnologia limpa para redução de impacto ambiental do cianeto na mineração de ouro

Riani, Josiani Costa; Pina, Pablo dos Santos; Leão, Versiane Albis
2007-03-01

Resumo em português Esse trabalho discute a aplicação de resinas de troca iônica com matriz poliacrílica para a adsorção de cianocomplexos metálicos. Ensaios em batelada mostraram que as resinas possuem elevada afinidade para os cianocomplexos de ferro e de zinco em relação aos de cobre. Já a eluição, estudada em coluna, indicou que soluções de tiocianato de sódio a 1mol/L são capazes de eluir os ciancomplexos dos três metais. Já soluções de nitrato de sódio, na mesma co (mais) ncentração, não são efetivas para a eluição do cianeto de zinco. Um processo de eluição seletiva é proposto onde os cianocomplexos de cobre e de ferro são eluídos com solução íons NO3-. Em seguida, o zinco é eluído com NaSCN. Ambos eluentes foram capazes de concentrar os cianocomplexos de solução, o que tem efeito benéfico nas etapas subseqüentes de regeneração do cianeto. Resumo em inglês A study on metal cyanocomplexes sorption on polyacrylic ion exchange resins has been undertaken. Batch sorption experiments have shown that polyacrylic resins have a high affinity for zinc and iron cyanides compared to copper complexes. Elution studies performed in column experiments have also depicted that 1mo/L sodium thiocyanate solutions can successfully extract the three metals. Conversely, sodium nitrate solutions at the same concentration are not effective in eluti (mais) ng zinc cyanocomplexes. Based on elution figures, it is proposed that copper and iron can be selectively eluted with nitrate before the zinc, this latter being recovered afterwards with thiocyanate solutions. Both eluants were able to concentrate the cyanocomplexes in solution with a beneficial effect on the subsequent steps of cyanide recycling.

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6

Sideróforos: uma resposta dos microorganismos/ Siderophores: a microorganism's answer

Benite, Anna Maria Canavarro; Machado, Sérgio de Paula; Machado, Bianca da Cunha
2002-12-01

Resumo em inglês Siderophores (from the Greek: "iron carriers") are defined as relatively low molecular weight, ferric ion specific chelating agents elaborated by microorganisms growing under low iron stress. The role of these compounds is to scavenge iron from the environment and to make this essential chemical element available to the microbial cell. The present paper is a brief presentation of siderophore coordination chemistry with emphasis on those aspects relevant to the transportat (mais) ion of iron (III) complexes across biological membranes. Finally, the role of siderophores in infection and their clinical potential as iron scavenging molecules are reviewed.

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7

Estudo de modelagem molecular de complexos ferriprotoporfirina-IX e quinolinocarbinolaminas antimaláricas: proposta de um farmacóforo/ Molecular modeling study of complexes between ferriprotoporphyrin IX and antimalarial 4-quinolinecarbinolamines: a proposal of pharmacophore

Silva, Thais Horta Álvares da; Oliveira, Marcelo Tavares de; Santos, Hélio Ferreira dos; Oliveira, Alaíde Braga de; De Almeida, Wagner Batista
2005-03-01

Resumo em inglês Quinine and quinidine are well-known 4-quinolinecarbinolamines that exhibit antimalarial activity, but, in contrast, their epimers 9-epiquinine and 9-epiquinidine are almost inactive. Literature data are conflicting in describing the 4-quinolinecarbinolamine interaction mode with the molecular target, the ferriprotoporphyrin IX [Fe(III)PPIX]. In the present paper, a pharmacophore is proposed based on the binding of the non-aromatic nitrogen to the iron atom. The 4-quinoli (mais) necarbinolamine antimalarials were superimposed on the pharmacophore under consideration and complexes with Fe(III)PPIX were constructed. Conformational analyses of the complexes were performed applying the MM+ molecular mechanics method. The analysis of the complexes showed that the proposed ligand mode is possible although it does not explain the activity differences between epimers. A discussion of the structural aspects is also provided.

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8

Construção de campo de força empírico para estudo de complexos de Fe(III) com interesse bioinorgânico/ Construction of the empirical force field for the study of iron (III) complexes with bioinorganic interest

Herrer, Juan Omar M.; Paes, Lílian Coelho; Benites, Anna Maria Canavarro; Marchiori, Roberto; Machado, Sérgio P.; Machado, Bianca C.
2006-04-01

Resumo em inglês In this work we present a new parametrization in molecular mechanics for studying iron complexes. This force field was implemented in the FORCES 2000 program, developed in our group for studying in coordination compounds of interest in bioinorganic chemistry. Mononuclear and dinuclear iron complexes were studied using this program with good success.

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9

Comportamento do ácido fítico na presença de Fe(II) e Fe(III)/ Behaviour of phytic acid in the presence of iron(II) and iron(III)

Quirrenbach, Hanna Raquel; Kanumfre, Francieli; Rosso, Neiva Deliberali; Carvalho Filho, Marco Aurélio
2009-03-01

Resumo em português O ácido fítico, dependendo do valor de pH, apresenta alto potencial quelante, complexando íons metálicos, inibindo, assim, a produção de espécies reativas de oxigênio, responsáveis pela destruição oxidativa em sistemas biológicos. Esse potencial quelante tem fundamentado diversos estudos aplicados à ação antioxidante em produtos alimentícios. O objetivo deste trabalho foi estudar o grau de interação do ácido fítico com os íons metálicos Fe(II) e Fe(I (mais) II), de importância biológica, em condições próximas às fisiológicas, e a estabilidade destes complexos. Titulações potenciométricas foram conduzidas para determinar as constantes de formação dos complexos ácido fítico-Fe(II) e ácido fítico-Fe(III) em solução aquosa, atmosfera inerte, força iônica 0,100 mol.L-1 de cloreto de potássio e à temperatura de 36 ± 0,1 ºC. Estudos espectroscópicos na região do UV-Vis foram realizados para acompanhar a formação dos complexos em solução. Os complexos ácido fítico-Fe(II) e ácido fítico-Fe(III) foram sintetizados e caracterizados por espectroscopia de absorção na região do infravermelho e por estudos termoanalíticos. Os resultados do conjunto de técnicas utilizadas evidenciaram, tanto em solução como no estado sólido, a presença dos íons metálicos coordenados ao ácido fítico. Resumo em inglês Depending on the pH value, phytic acid presents high chelating potential bonding metallic ions thus inhibiting the production of reactivated oxygen species, which are responsible for the oxidative destruction in biological systems. Such chelating potential has been the basis of several studies on the antioxidant action in food products. The objective of this work was to study the degree of interaction of the phytic acid with the metallic ions Fe(II) and Fe(III), of biolog (mais) ical importance, in near-physiological conditions and the stability of these complexes. Potentiometric titrations were applied to determine the constants of formation of the complexes phytic acid-Fe(II) and phytic acid-Fe(III) in aqueous solution, inert atmosphere, ionic strength of 0.100 mol.L-1 in potassium chloride, and temperature at 36 ± 0,1 ºC. UV-Vis spectroscopic studies in the were conducted to investigate the formation of the complexes in the solution. The complexes phytic acid-Fe(II) and phytic acid-Fe(III) were synthesized and characterized by infrared absorption spectroscopy and by thermoanalytical studies. The results indicate the bonding of the metallic ions and the phytic acid both in solution and in the solid state.

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10

A "fração argila" dos solos do Estado de São Paulo e seu estudo roentgenográfico

Paiva Neto, J. E. de
1942-01-01

Resumo em inglês In the beginning of this work a brief idea was given on what is understood as "clay", on the scientific methods applied to the study of the matter "clay" as well as on its conception with regard to the edaphic studies. A description is given of the methods of total and natural mechanical analyses which were employed in the agro-geological Department. The work is illustrated by a graphic showing the fractions of the mechanical analysis of the chief great soil types of the (mais) State of São Paulo. The fraction clay is then studied by chemical way in the following sequence : 1.° total chemical analysis, 2.° partial chemical analysis, 3.° chemical analysis of the Helmholz layer and 4.° study of the fixation of the ion Ca+ + in the already mentioned Helmholz layer. The first analysis separates and attacks the hydrated aluminium silicates, the hydrated oxyds of iron and aluminium, manganese, etc. In this analysis the relationship between silica and sesquioxyds was determined. The second type of attack or chemical analysis does not affect the hydrated silicates of aluminium, all others go in dissolution. In this analysis were determined chiefly the sesquioxyds in their free form in the clay complex. For the study of the Helmholz layer, i.e. the determination of changeable ions, solutes of NH4Cl N/l, HNO3 N/5, KCl N/l, etc. were used, percolation of these liquids being made through a layer of air dried soil. The relationship between soil and liquid was always 1:10. In this analysis, principally the cations K+, Ca++, Mg++, Al+ + +, H+ etc. were determined. With such determinations the calculations of the following values were obtained: S = sum of the changeable bases in ME; T = total value in ME of the sorptive power of the complex in each 100 g dried soil at 110° C. and V = percentage of saturation of the complexes with bases. Finally, the qualitative radiographic analysis of the fraction clay was carried out by means of the Debye-Scherrer-Hull method. For these studies the Siemens-Berlin apparatus was used, the transformer of which runs with all0-220 volts 60-cycle alternating current. The bulb has a copper anti-cathode and is fed by a current of 13 m.A. of intensity and the difference of potential is of 30,000, 35,000 and 47,000 volts. The flash of X-rays goes through the nickel filter in order to free it of the b irradiations which are deleterious. In this way, inciding vertically on the preparation, radiations CuK a with l = 1,539 A are obtained. The sensible film used was a Lawe-Film-Agfa, with an exposure going from 11/2 to 2 hours with 35,000 V. The chassis has a diameter of 57 mm. More than 500 radiographs of soil samples were taken, of those proceding from all districts of the State, 79 of which are presented in the present work. With this material the different constituents of the clay minerals contained in our soils were known. Thus, in the soils over the Archean geological formation, kaolinite is represented most frequently and abundantly ; the hydrargillite also appears commonly. The soils over the Glacial formation contain the same representatives and oscillations as those just mentioned. In the Corum-batai formation, quartz is the most important constituent. The Botucatu formation (lava) is that which gave origin to our legitimate red soils ; the mineralogical clay constituents of these soils are : 1.° large amount of hydrated oxyds of iron up to 35% of Fe2O3 for each 100 g of soil at 110° C. ; 2.° hydrargillite and 3.° kaolinite. The amount of the latter in the clay complex ranges between 9 and 25%. The sandy soils existing in the geological formations of lower and upper Baurú bear in their clays the following mineralogical constituents : 1.° kaolinite, 2.° montmorrillonitic type (on the upper Baurú only), 3.° hydrargillite (more common on the lower Baurú) and 4.° quartz, generally, in small percentages. These researches made it evident that the constituents of the clay fraction of our soils commonly have a small sorptive power related to the cations; it follows hence that they do not show a great power of retention of manure with the exception of the montmorrillonitic type.

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