Synthesis and characterization of Fe(III)-piperazine-derived complexes encapsulated in zeolite Y

Zeolite-encapsulated complexes have been widely applied in hydrocarbon oxidation catalysis. The "ship-in-a-bottle" encapsulation of iron(III) complexes containing piperazine and piperazine-derivative ligands in zeolite-Y is described. The flexible ligand methodology was employed and the efficiency and reproducibility of the procedure was investigated. The catalysts were characterized employing several techniques and the results indicate the presence of coordinated and uncoordinated iron(III) ions inside and outside the zeolitic cage.

Determinação de Cu, Fe, Mn, Zn e do teor de proteína total em amostras de trigo e soja após procedimento de extração sequencial

A sequential extraction procedure was applied to wheat and soybean seed samples. The total protein content (determined by two distinct methods: Bradford and bicinchoninic acid-BCA) and distribution of Cu, Fe, Mn and Zn in each fraction was determined. The sequential extraction employed four different solutions: water, 0.5 mol L-1 NaCl, ethanol/water (70:30 v v-1) and 0.5 mol L-1 NaOH. For both samples, the highest concentration of metals was observed in those extracts associated with globulin-type proteins using NaCl solution. Regarding protein content, higher levels were obtained using the BCA method.

Distribuição de Zn, Pb, Ni, Cu, Mn e Fe nas frações do sedimento superficial do Rio Cachoeira na região sul da Bahia, Brasil

The metal distribution in the surface sediment fractions of the Cachoeira River was evaluated based on the fractionation method using a five-step sequential extraction. The determination of metals was made by flame atomic absorption spectrophotometry (F AAS). Zn, Pb and Cu exhibit higher concentrations in the residual fraction of the sediment from sites that receive discharges from urban and industrial zones. High levels of Ni (60 ± 1 to 447 ± 9 µg L-1) were found in the river water, which may be detrimental to the "health" of rural communities that utilize the river water for domestic purposes without treatment.

Avaliação da mineralização de arroz em sistema de refluxo para a determinação de Cu, Fe, Mn e Zn por FAAS

This paper describes the evaluation of a new method of sample preparation using a cold finger system with continuous water flow for rice analysis by flame atomic absorption spectrometry. The limits of detection for Cu, Fe, Mn and Zn for the proposed method were 0.36, 1.84, 2.12 and 0.16 mg kg-1, respectively. The RSDs were lower than 6.0% for all elements and the CRM analyzed showed values with 95% agreement. The proposed method is simple and safe for the proposed objective and does not require the use of mixtures of acid or special equipment for sample preparation.

Preparation and evaluation of magnetic chitosan particles modified with ethylenediamine and Fe(III) for the removal of Cr(VI) from aqueous solutions

The adsorption of Cr(VI) in aqueous solution by magnetic particles of crosslinked chitosan-ethylenediamine-Fe(III) (MPCh-EDA-FeCL) was studied in a batch system. Fe3+ in the MPCh-EDA-FeCL permitted that adsorption of Cr(VI) occurred with maximum efficiency between pH 3 and 11. The maximum adsorption capacity at pH 7.0 was 81.04 mg g-1 at 25 ºC. The adsorption kinetic process was described by the pseudo-second-order model. Thermodynamic parameters indicated spontaneous, exothermic and chemical adsorption nature. The adsorbent was successively regenerated using a 0.1 mol L-1 NaOH solution. Results were satisfactory for treatment of wastewater from the electroplating industry.

ANÁLISE EXPLORATÓRIA DAS CONCENTRAÇÕES DOS METAIS NA, CA, MG, SR E FE EM EXTRATO AQUOSO DE PETRÓLEO, DETERMINADOS POR ICP OES, APÓS OTIMIZAÇÃO EMPREGANDO PLANEJAMENTO DE EXPERIMENTOS

AbstractThe purpose of this study was to evaluate the best operating conditions of ICP OES for the determination of Na, Ca, Mg, Sr and Fe in aqueous extract of crude oil obtained after hot extraction with organic solvents (ASTM D 6470-99 modified). Thus, the full factorial design and central composite design were used to optimize the best conditions for the flow of nebulization gas, the flow of auxiliary gas, and radio frequency power. After optimization of variables, a study to obtain correct classification of the 18 samples of aqueous extract of crude oils (E1 to E18) from three production and refining fields was carried out. Exploratory analysis of these extracts was performed by principal component analysis (PCA), hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA), using the original variables as the concentration of the metals Na, Ca, Mg, Sr and Fe determined by ICP OES.

Thermal decomposition and stability in a series of heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X=Cl, Br, I)

Heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X= Cl, Br, I), which have metal-metal bonds, have been prepared in order to study their thermal stabilities as a function of the halogen coordinated to mercury atoms. The characterization of the above complexes was carried out by elemental analysis, IR and NMR spectroscopies. Their thermal behaviour has been investigated and the final product was identified by IR spectroscopy and by X-ray powder diffractogram.

Estudo eletroquímico de Fe[Fe(CN)5NO] em eletrodo de pasta de grafite

Nitroprussiato de ferro (FeNP) foi sintetisado e caracterizado por Infravermelho e absorção atômica. FeNP foi incorporado em eletrodo de pasta de grafite empregando-se como técnica de estudo a voltametria cíclica. O comportamento eletroquímico do eletrodo de pasta de grafite contendo FeNP apresenta dois processos eletródicos com potencial médio (Em) de (Em)1 = 0,24 V e (Em)2 = 0,85 V ( KCl =1,0M; v = 20 mV.s-1 vs ECS) atribuídos aos pares redox ( FeII/FeIII ) e FeII(CN)5NO/ FeIII(CN)5NO, respectivamente. A intensidade de corrente dos pares redox aumenta, linearmente com a velocidade de varredura indicando um controle de adsorção. O eletrodo de pasta de grafite modificada com FeNP apresenta estabilidade por vários dias. O estudo eletroquímico do eletrodo de pasta de grafite modificada com FeNP foi examinado em várias soluções de eletrólitos suporte sendo que a natureza do cátion afetam a intensidade de corrente e os potenciais dos pares redox ,deslocando (Em)1 para potenciais mais positivos na sequência: K+ >Na+>Li+ enquanto que a natureza do anion (Cl-, NO3-,SO4=) não afeta os pares redox. Os voltamogramas obtidos em diferentes concentrações de KCl (0,05 - 2,5 M)exibem deslocamentos do (Em)1 para potencial de valores mais positivos. Este deslocamento é linear com a variação da concentração do eletrólito suporte. A inclinação da reta é de 66 mV por década de concentração indicando a ocorrência de um processo quase nernstiano. O potencial médio permanece praticamente constante em pH entre os valores de 3,0 e 8,0. Um outro processo eletródico com (Em)3 = 0,47 V ocorre em pH < 3, sendo este atribuído a formação de novas espécies intermediárias.

Determinação direta e simultânea de Al, As, Fe, Mn e Ni em cachaça por espectrometria de absorção atômica em forno de grafite

Este trabalho propõe um método simples, rápido e confiável para determinação direta e simultânea de Al, As, Fe, Mn e Ni em cachaça por espectrometria de absorção atômica em forno de grafite (GFAAS). A superfície superior da plataforma do tubo de grafite foi revestida com filme à base de tungstênio (WxCyOz).O programa de aquecimento otimizado (temperatura, tempo de rampa, tempo de patamar) foi o seguinte: secagem 1 (100ºC, 5 s, 5 s); secagem 2 (120ºC, 5 s, 5 s); pirólise (1300ºC, 10 s, 30 s); atomização (2200ºC, 1 s, 6 s) e limpeza (2550ºC, 1 s, 3s). Os desvios padrões relativos (n=3) foram < 4,4%, < 0,7%, < 11%, < 6,0%, < 1,2% para os elementos Al, As, Fe, Mn e Ni, respectivamente. A exatidão foi avaliada por meio de testes de adição e recuperação dos analitos em 8 amostras de cachaças comerciais, e as recuperações situaram-se nos seguintes intervalos: 80 - 105% (Al), 81 - 92% (As), 82 - 108% (Fe), 83 - 106% (Mn), 83 - 108% (Ni). Os limites de detecção calculados foram 9,7 µg L-1 Al, 2,3 µg L-1 As, 12 µg L-1 Fe, 14 µg L-1 Mn e 0,8 µg L-1 Ni.

Electrochemical and physical characterization of Ni-Cu-Fe alloy for chlor-alkali hydrogen cathodes

This work describes the development of an alternative acetate bath for the electrochemical codeposition of Ni-Cu-Fe electrodes at low pH that is stable for several weeks and produces electrodes with good performance for chlor-alkali electrolysis. Physical characterization of the electrode surface was made using X ray absorption spectroscopy (XAS), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). The evaluation of the material as electrocatalyst for the hydrogen evolution reaction (her) was carried out in brine solution (160 g L-1 NaCl + 150 g L-1 NaOH) at different temperatures through steady-state polarization curves. The Ni-Cu-Fe electrodes obtained with this bath have shown low overpotentials for the her, around 0.150 V at 353 K, and good stability under continuous long-term operation for 260 hours. One positive aspect of this cathode is that the polarization behavior of the material shows only one Tafel slope over the temperature range of 298 - 353 K.

Reatividade do [Fe(CO)2(eta2-CS2)(PPh 3)2] frente a compostos de Cu(I): síntese de espécies binucleares heterometálicas contendo CS2 em ponte entre Fe(0) e Cu(I)

Este trabalho contempla a síntese e caracterização espectroscópica de dois compostos carbonílicos heterometálicos do tipo [Fe(CO)3(m-CS2)(PPh3 )(CuX)], X = Cl, ClO4. Os dados provenientes da espectroscopia no infravermelho e de RMN de 31P{¹H} foram conclusivos quanto à proposição da geometria octaédrica distorcida ao redor do átomo de ferro (0), como também sobre a natureza bimetálica de ambos compostos. Estes dados esclareceram o modo de coordenação dos grupos carbonilos, da trifenilfosfina (PPh3), bem como a disposição do ligante dissulfeto de carbono em ponte entre os átomos de Fe (0) e Cu (I).

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Pure and Fe(III)-doped TiO2 suspensions were prepared by the sol gel method with the use of titanium isopropoxide (Ti(OPri)4) as precursor material. The properties of doped materials were compared to TiO2 properties based on the characterization by thermal analysis (TG-DTA and DSC), X-ray powder diffractometry and spectroscopy measurements (FTIR). Both undoped and doped TiO2 suspensions were used to coat metallic substrate as a mean to make thin-film electrodes. Thermal treatment of the precursors at 400ºC for 2 h in air resulted in the formation of nanocrystalline anatase TiO2. The thin-film electrodes were tested with respect to their photocatalytic performance for degradation of a textile dye in aqueous solution. The plain TiO2 remains as the best catalyst at the conditions used in this report.

Danos causados pelo Zucchini lethal chlorosis virus (ZLCV) sobre a produção de frutos comerciais de abobrinha de moita 'Caserta'

O ZLCV é um tospovírus encontrado com freqüência causando severos danos em cucurbitáceas. Nesse trabalho avaliaram-se os danos causados pelo ZLCV em abobrinha de moita 'Caserta', em campo na ESALQ/USP, Piracicaba-SP, onde esse vírus é freqüente. Plantas obtidas pela semeadura direta foram monitoradas periodicamente quanto à infecção pelo ZLCV por meio dos sintomas e por PTA-ELISA. Monitorou-se ainda a contaminação com Papaya ringspot virus - type W e Zucchini yellow mosaic virus, desconsiderando a produção dessas plantas. As plantas foram agrupadas em função da época de aparecimento dos sintomas do ZLCV, avaliando a produção de frutos comerciais (FC) e não comerciais (FNC) de cada grupo e comparando com a de plantas que permaneceram sem sintomas até o final do experimento. As plantas que apresentaram sintomas até os 23 dias após a emergência (DAE) não produziram qualquer tipo de frutos. FC foram colhidos de plantas que apresentaram sintomas a partir dos 42 DAE. Mesmo assim, houve redução de 78,5 % na produção de FC. Plantas que mostraram sintomas por ocasião da última colheita (55 DAE) apresentaram redução na produção de FC de 9,6 %. A infecção com o ZLCV até o início da frutificação inviabiliza a produção de FC de abobrinha de moita 'Caserta'.

Operational parameters of soybean seeding in santa fe system

The use of no tillage system associated with the crop-livestock integration is an alternate managing that promotes the accumulation of dry matter in the soil, an essential fact to make the system sustainable and profitable. The aim of this study was to evaluate the operational performance of a planter-tractor set on maize straws intercropped with Urochloa, in different seeding modes. The soybean crop was seed on the intercropping of two forage species (Urochloa brizantha and Urochloa ruziziensis) in five cropping systems: MBL (Maize with Urochloa in the maize seeding row, mixed with base fertilizer and deposited at 0.10 m), MBE (Maize with Urochloa seeded between rows at the same day of seeding maize), MBC (Urochloa between rows of maize seeded with the covering fertilizer at the V4 stage), MBLA (Maize with Urochloa by broadcast seeding at the V4 stage ) and MS (Single Maize: control). The following variables were evaluated: dry mass of maize straw, dry mass of forages and total dry mass of straw; and for the operational parameters the speed of seeding, wheel slippage, traction force and average power at the drawbar. The results showed that the amount of straw produced by maize intercropping with Urochloa, interferes in the operational performance of the tractor-planter at the operation of soybean seeding, i.e., areas with higher amount of straw promote greater energy demand, as well as higher wheel slippage.