Study of an organically modified clay: Selective adsorption of heavy metal ions and voltammetric determination of mercury(II)

In this work, a hydrophilic clay, Na-montmorillonite from Wyoming, USA, was rendered organophilic by exchanging the inorganic interlayer cations for hexaclecyltrimethylammonium ions (HDTA), with the formulae of [(CH3)(3)N(C16H33)](+) ion. Based on fact that organo-clay has high affinities for non-ionic organic molecules, 1,3,4-thiadiazole-2,5-dithiol was loaded oil the HDTA-montmorillonite surface, resulting in the 1,3,4-thiadiazole-2,5-dithiol-HDTA-montmorillonite complex (TDD-organo-clay).The following properties of TDD-organo-clay are discussed: selective adsorption of heavy metal ions measured by batch and chromatographic column techniques, and utilization as preconcentration agent in a chemically modified carbon paste electrode (CMCPE) for determination of mercury(II).The main point of this paper is the construction of a selective sensor, a carbon paste electrode modified with TDD-organo-clay, its properties and its application to the determination of mercury(II) ions, as this element belongs to the most toxic metals. The chemical selectivity of this functional group and the selectivity of voltammetry were combined for preconcentration and determination. (c) 2005 Elsevier B.V. All rights reserved.

Organic complexation and translocation of ferric iron in podzols of the Negro River watershed. Separation of secondary Fe species from Al species

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Soil humus characteristics in virgin and cleared areas of the paraná river basin in Brazil

A study of the characteristics and distribution of the soil humus fractions in representative ecosystems of central Brazil was carried out with special emphasis on the comparison between the soils under virgin vegetation-Cerrado-and those subjected to cultivation. In spite of the contrasted vegetation and cultural practices in the sites studied, the soil humus showed analogous characteristics: there was a negligible amount of plant residues, the humic and fulvic acids amounted to approximately 70% of the total organic carbon, and about 40% of these humic substances were in extremely stable association with the soil mineral fraction, the HCl-HF treatment being required for their extraction. The stability of such organo-mineral complexes increased slightly in the cultured sites. The study of the humic acid fraction showed increased oxidation and aromaticity in most of the cultivated sites: the lowest values for the IR alkyl vibrations and H/C atomic ratios and the highest ones for the optical density at 465 nm were observed in sites transformed into orchards, whereas the above changes were small in those used as pasture. The 14C NMR spectra confirmed that the proportion of polyalkyl structures decreased in the humic acids of soils subjected to cultivation, as opposed to that of carboxyl groups. In spite of the high stability inferred for the organic matter throughout the wide area examined, the samples from the original Cerrado as well as from those transformed into pastures showed, in laboratory conditions, higher mineralization rates than those from the sites subjected to cultivation. This is partly attributed to the decreased proportions of extractable humic substances in the latter. © 1992.

Influência das propriedades de granulados de lactose nas características físicas dos comprimidos

The compaction behavior of powdered solids used in tablets can be dominated by the physical-chemical properties of the excipients because, frequently, they are present in much larger amounts than the drug in tablet formulation. The aim of this study was to evaluate the influence of the size of lactose granules on the physical characteristics of tablets produced in punches of various diameters, since this relation has not been explored in the literature. Granules were produced in several sizes by wet granulation and compressed in punches of different diameters by applying different forces. Size distribution, apparent density and flow of granules were evaluated, as well as the physical characteristics of the tablets (weight, friability, hardness and disintegration time). The results indicate that in situations where excipient characteristics predominate due to low drug content, as in the 7 mm punch, the selection of granule size is important for the mechanical strength of tablet. On the other hand, with the 9, 11 and 13mm punches, it was possible to produce strong tablet from all sizes of granules.

Produtividade de cana-de-açúcar sob adubação com torta de filtro enriquecida com fosfato solúvel

Phosphorus is considered an essential element for plants and it is found in small amounts in Brazilian soils. The filter cake residue, composed of a mixture of bagasse and decanting sludge, has high levels of organic matter, phosphorus and calcium. The phosphorus present in the filter cake is organic, and its release, as it happens to the nitrogen, occurs gradually by mineralization and by microorganisms attack in the soil. This study aimed to evaluate sugarcane vegetative growth and yield under fertilization with filter cake enriched with soluble phosphate. The experiment was carried out in Presidente Prudente, São Paulo State, Brazil, by using a randomized complete block design, in a 5x4 factorial scheme, where the first factor consisted of filter cake doses (0 t ha-1, 0.5 t ha-1, 1.0 t ha-1, 2.0 t ha-1, and 4.0 t ha-1) and the second of phosphorus fertilizer doses (0 kg ha-1, 50 kg ha -1, 100 kg ha-1, and 200 kg ha-1 of P 2O5), with 4 repetitions, totalizing 80 plots. The experiment evaluated the tiller number, at 30, 60, 90, and 120 days after planting, oBrix, and yield. The stalk yield and tillering were influenced by the filter cake rates applied to the soil. Filter cake doses and their combination with phosphate did not change the juice quality (Brix) at harvest.

Study of adsorption and preconcentration by using a new silica organomodified with [3-(2,2′-dipyridylamine)propyl] groups

In this work, a silica surface chemically modified with [3-(2,2′-dipyridylamine)propyl] groups, named [3-(2,2′- dipyridylamine)propyl]silica (Si-Pr-DPA) was prepared, characterized, and evaluated for its heavy metal adsorption characteristics from aqueous solution. To our knowledge, we are the first authors who have reported the present modification. The material was characterized using infrared spectroscopy, SEM, and NMR 29Si and 13C solid state. Batch and column experiments were conducted to investigate for heavy metal removal from dilute aqueous solution by sorption onto Si-Pr-DPA. From a number of studies the affinity of various metal ions for the Si-Pr-DPA sorbent was determined to follow the order Fe(III) > Cr(III) >> Cu(II) > Cd(II) > Pb(II) > Ni(II). Two standard reference materials were used for checking the accuracy and precision of the method. The proposed method was successfully applied to the analysis of environmental samples. This ligand material has great advantage for adsorption of transition-metal ions from aqueous medium due to its high degree of organofunctionalization associated with the large adsorption capacity, reutilization possibility, and rapidity in reaching the equilibrium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PLA and Montmorilonite Nanocomposites: Properties, Biodegradation and Potential Toxicity

The concern related to solid waste increases efforts to develop products based on biodegradable materials. At present, PLA has one of the highest potentials among biopolyesters, particularly for packaging. However, its application is limited in some fields. In order to optimize PLA properties, organo-modified montmorilonites have been extensively used to obtain nanocomposites. Although PLA nanocomposites studies are widely reported in the literature, there is still few information about the influence of organoclays on de biodegradation process, which is a relevant information, since one of the main purposals related to the final disposal of biopolymers as PLA is composting. Besides, in the last years some research has been conducted in order to evaluate the potential toxicity of montmorilonite, unmodified or organo-modified. Since the use of montmorilonite is expanding in different applications, human exposure and risk assessment are important issues to be investigated. In this context, this review intends to compile available information related to common organoclays used for PLA nanocomposites, its properties, biodegradation analysis and potential toxicity evaluation of nanocomposites, focused on montmorilonite as filler. Two issues of relevance were pointed out. The first is food safety and quality, and the second consideration is the environmental effect. © 2013 Springer Science+Business Media New York.

Momentos nulos e regularidade wavelet na detecção de falhas em sinais

Pós-graduação em Engenharia Elétrica - FEIS

Geração automática de código para microcontroladores aplicada a um ambiente de co-projeto de hardware e software

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Propriedade antimicrobiana de óleos essenciais de plantas condimentares com potencial de uso como conservante em carne e hambúrguer bovino e testes de aceitação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Solução numérica das equações de Navier-Stokes em um canal-tipo estenose usando métodos compactos e não compacos de alta ordem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Atividade antibacteriana de óleos essenciais de especiarias em alimentos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Labor preparatoria relativa a la documentación básica que habrá de presentarse a la Conferencia Mundial

Propone un criterio para la formulacion de estrategias para el adelanto de la mujer hasta el ano 2000 en el contexto de las metas y objetivos y subtemas del Decenio de las NU para la mujer. Sugiere un esbozo del informe que se ha de presentar al organo preparatorio de la Conferencia Mundial, en su tercer periodo de sesiones en 1985, incluidas las principales cuestiones que se han de abordar.

Uso de antioxidantes naturais em hambúrgueres preparados com carne mecanicamente sepada de tilápia

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanocompósitos baseados no sistema epoxídico DEGBA/DETA modificado com uma resina epoxídica de silsesquioxano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)