[Co(en)(3)][Sb12S19]: a new antimony sulfide with a zeolite-like structure containing one-dimensional channels

Solvothermal synthesis affords access to the first truly three-dimensional anti mony-sufide framework which contains one-dimensional circular channels.

Rheological and electrical properties of NaY zeolite electrorheological fluid

The relations between the rheological and electrical properties of NaY zeolite electrorheological fluid and its solid phase are studied. It is found that then exist complex relations between its electrical and theological properties. The temperature spectra of dielectric properties of the fluid under high AC electric field are strongly field strength dependent. The relation between the DC conductivity of the fluid and the exciting electric field is experimentally presented as log sigma =A+BE1/2, when A is a strong function, but B, a very weak function of temperature. The shear stress of the fluid under a fixed electric field and temperature decreases with shear rate. A relaxation time for the adsorbed charges is estimated to be about 0.3 to 6.6 s in the temperature range from 280 to 380 K. The relaxation time qualitatively corresponds to the shear rate at which the shear stress begins to drop. The time dependent leaking current of the ER fluids under DC electric field is also measured. The conductivity increase is mainly caused by the structure evolution of particles. The experimental results can he explained with the calculations of Davis (J. Appl. Phys. 81(1997) pp.1985-1991) and Martin (J. Chem. Phys. 110(1999) pp.4854-4866). It is predicted that the NaY zeolite ER fluid strength would get degraded slowly.

Antimicrobial and mechanical properties of acrylic resins with incorporated silver-zinc zeolite - part I

Objective: The purpose of this in vitro study was to evaluate the antimicrobial activity of acrylic resins containing different percentages of silver and zinc zeolite, and to assess whether the addition of zeolite alters the flexural and impact strength of the resins. Background: The characteristics of acrylic resins support microorganism development that can threaten the health of the dentures user. Material and methods: A microwave-polymerised (Onda-Cryl) and two heat-polymerised (QC20 and Lucitone 550) acrylic resins were used. The materials were handled according to the manufacturers` instructions. Fifty rectangular-shaped specimens (8 x 10 x 4mm) were fabricated from each resin and assigned to 5 groups (n = 10) according to their percentage of Irgaguard B5000 silver-zinc zeolite (0%- control, 2.5%, 5.0%, 7.5% and 10%). Flexural strength and Izod impact strength were evaluated. The antimicrobial activity against two strains of Candida albicans and two strains of Streptococcus mutans was assessed by agar diffusion method. Data were analysed statistically by one-way ANOVA and Tukey`s test at 5% significance level. Results: The addition of 2.5% of Irgaguard B5000 to the materials resulted in antimicrobial activity against all strains. Flexural strength decreased significantly with the addition of 2.5% (QC20 and Lucitone 550) and 5.0% (Onda-Cryl) of Irgaguard B5000. The impact strength decreased significantly with the addition of 2.5% (Lucitone 550) and 5.0% (QC20 and Onda-Cryl) of zeolite. Conclusion: The addition of silver-zinc zeolite to acrylic resins yields antimicrobial activity, but may affect negatively the mechanical properties, depending on the percentage of zeolite.

Evaluation of the zinox and zeolite materials as adsorbents to remove H2S from natural gas

MELO, Dulce Maria de Araújo et al. Evaluation of the Zinox and Zeolite materials as adsorbents to remove H2S from natural gas. Colloids and Surfaces. A, Physicochemical and Engineering Aspects, Estados Unidos, v. 272, p. 32-36, 2006.

Voltammetric determination of L-dopa using an electrode modified with trinuclear ruthenium ammine complex (Ru-red) supported on Y-type zeolite

The L-dopa is the immediate precursor of the neurotransmitter dopamine. Unlike dopamine, L-dopa easily enters the central nervous system and is used in the treatment of Parkinson's disease. A sensitive and selective method is presented for the voltammetric determination of L-dopa in pharmaceutical formulations using a carbon paste electrode modified with trinuclear ruthenium ammine complex [(NH3)(5)Ru-III-O-Ru-IV(NH3)(4)-O-Ru-III(NH3)(5)](6+) (Ru-red) incorporated in NaY zeolite. The parameters which influence on the electrode response (paste composition, potential scan rate, pH and interference) were also investigated. The optimum conditions were found to an electrode composition (m/m) of 25% zeolite containing 6.7% Ru, 50% graphite and 25% mineral oil in acetate buffer at pH 4.8. Voltammetric peak currents showed a linear response for L-dopa concentration in the range between 1.2 x 10(-4) and 1.0 x 10(-2) Mol l(-1) (r = 0.9988) with a detection limit of 8.5 x 10(-5) mol l(-1). The variation coefficient for a 1.0 x 10(-3) mol l(-1) L-dopa (n = 10) was 5.5%. The results obtained for L-dopa in pharmaceutical formulations (tablet) was in agreement with compared official method. In conclusion, this study has illustrated that the proposed electrode modified with Ru-red incorporated zeolite is suitable valuable for selective measurements of L-dopa. (C) 2004 Elsevier B.V. All rights reserved.

Encapsulation of titanium (IV) silsesquioxane into the NH4USY zeolite: Preparation, characterization and application

This work describes the encapsulation of titanium (IV) silsesquioxane into the supercavities of NH4USY ultra stabilized zeolite, after chemical treatment. The modified zeolite was characterized by Fourier transform infrared spectra, Nuclear magnetic resonance, scanning electronic microscopy, X-ray diffraction and thermogravity. This encapsulated titanium (IV) silsesquioxane can adsorb Azure A chloride after treatment with H3PO4, without modifier leaching problems. In an electrochemical study, the cyclic voltammograms of the graphite paste modified electrode, shows two redox couples with formal potential (E-0) -0. 1 V and 0.21 V to I and II redox couples respectively (v = 700 mV s(-1); Britton Robinson buffer (B-R) solution, pH 3) versus SCE ascribed to a monomer and dimmer of azure. This paper shows the use of ultra stabilized zeolite in the electrochemical field as host for molecules with nanometric dimensions. (c) 2006 Elsevier Ltd. All rights reserved.

Utilização de rejeitos de Caulins na Síntese de Zeólita A

Three studies were performed using tailings kaolin for the synthesis of zeolite A. The first synthesis of zeolite A was performed using a kaolin waste generated from the beneficiation of kaolin for paper production process was studied. The kaolin waste was thermally activated at a temperature range of 550-800°C. For comparison was performed a synthesis pattern of Zeolite A(procedure IZA). The prepared materials were characterized by 27Al MAS NMR, X-ray diffraction and scanning electron microscopy with microprobe rays. The pre-tramento proved to be the most appropriate and suitable temperatures are between 600 and 700°C. Observed the formation of zeolite A in all materials, reaching 52% crystallinity, and the presence of phase sodalite and amorphous material. The second study was the use of a highly reactive metakaolin originating from the Jari region in the synthesis of zeolite A by a new method of hydrothermal synthesis. The zeolite is obtained pure and highly crystalline employing the Jari kaolin calcined at 600 ° C for 2h when the transformation to metakaolin occurs. Get to zeolite phase A at 4pm. The best crystallization time was of 24 h afforded a crystallinity of 67.9%. The third study was the evaluation of the NaOH / metakaolin and crystallization time on the synthesis of zeolite NaA from a sample of kaolin waste, named Kaolin Coverage. The experiments were performed using statistical design (axial points) and rejoinder the center point. The samples were characterized by X-ray diffraction (XRD), scanning microscopic analysis and chemical analysis using an EPMA microprobe. The results showed that a relationship exists between the amount of NaOH added and the crystallization time. The experiment performed using the lowest ratio NaOH / metakaolin (0.5) and shorter (4 h) produced an amorphous material. The increase ratio of NaOH / metakaolin and crystallization time leads to formation of a more crystalline NaA phase, but the presence of phase with sodalite as impurities

Quantitative estimation of Br, Cl, K and Na in sample blood by NAA

Neutron activation analysis, using Au as flux monitor, was applied to determine the concentrations of Br, Cl, K and Na in blood of healthy male and female blood donors, selected from blood banks and hematological laboratories from different regions of Brazil. The aims of this study were to collect more reference values of the Brazilian population as well as to perform hematological investigations. The advantages as well as the limitations of using this nuclear procedure are discussed.

Enraizamento de estacas de pinheira (Annona squamosa L.), gravioleira (Annona muricata L.) e atemoeira (Annona squamosa L. x Annona cherimola L.) tratadas com ácido indolbutírico (IBA), ácido naftalenoacético (NAA) e bioestimulante

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis and characterization of zeolite NaP using kaolin waste as a source of silicon and aluminum

The synthesis of zeolite NaP using kaolin waste, from the Amazon region, as a predominant source of silicon and aluminum has been studied. The zeolitisation process occurred in hydrothermal conditions using static autoclaving and the effects of time, temperature, and the Si/Al ratio were investigated. The starting material and the phases formed as reaction products were characterized by XRD, SEM and FTIR. The results showed that pure zeolite NaP is hydrothermally synthesized, at 100 °C for 20 hours, using metakaolin waste material in alkaline medium in presence of additional silica. The XRD and SEM analyses indicate that the synthesized zeolite presents good crystallinity.

Síntese de pigmentos zeolíticos a partir de zeólita A derivada de rejeito de caulim da Amazônia

Pigmentos tipo ultramar foram sintetizados com sucesso a partir de zeólita NaA derivada de caulim e rejeito de caulim. Tal rejeito tem sido uma excelente fonte de silício e alumínio na síntese de zeólitas, por ser uma matéria-prima “natural” com alta concentração de caulinita e baixos teores de impurezas, além do menor custo em comparação àquelas matérias-primas industrializadas. A zeólita NaA derivada de tal rejeito apresenta características estruturais favoráveis a síntese de pigmentos ultramar, sua estrutura encapsula as espécies de enxofre formadas, que agem como cromóforos, e impedem que essas espécies se oxidem e seja liberado elevados teores de gases tóxicos durante a reação. Zeólita NaA foi misturada com enxofre e carbonato de sódio em diferentes proporções com o objetivo de verificar a influência dessa variação na cor e na tonalidade dos pigmentos. Após calcinação a 500 °C por 5 horas os produtos foram caracterizados por DRX, FRX e Raman, além da classificação visual por cor e tonalidade por meio de fotografias. O resultado foi produtos com coloração que variaram do azul ao verde com diferentes tonalidades, ambas influenciadas pela quantidade de aditivos, pela taxa de resfriamento após calcinação e pela granulometria. Assim, pode-se dizer que quantidades diferentes dos mesmos aditivos na mesma matriz zeolítica proporcionam aumento de intensidade da cor, que a taxa de resfriamento após calcinação e granulometria da matriz zeolítica provoca mudança da cor. A partir de DRX foi observado que a estrutura da zeólita NaA não é transformada para o tipo sodalita, como normalmente observado na literatura. Por espectroscopia Raman foram identificadas as espécies de enxofre responsáveis pela coloração no pigmento zeolítico, sendo: S₆ ^2- o responsável pela cor amarela e o S₃^- pela cor azul, e que a mistura dos dois resultou na cor verde, que predominou nesse trabalho. Por fim, o aproveitamento de rejeito de caulim na produção de pigmentos zeolíticos parece ser uma boa proposta de produção sustentável.

As-synthesized TEA-BEA zeolite: Effect of Si/Al ratio on the Knoevenagel condensation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

One-step glycerol oxidehydration to acrylic acid on multifunctional zeolite catalysts

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)