Modification of a Brazilian smectite clay with different quaternary ammonium salts

In this work, a smectite clay from the State of Paraiba, Brazil, was treated with six different types of ammonium salts, which is an usual method to enhance the affinity between the clay and polymer for the preparation of nanocomposites. The clays, before and after modification, were characterized by X ray diffraction. The conformation of the salts within the platelets of the clay depended on the number of long alkyl chains of the salt. The thermal stability of the clays was also studied. The ammonium salts thermal decomposition was explained in light of their position within the organoclays.

Chemical constituents of the wood from Zanthoxylum quinduense Tul. (Rutaceae)

Phytochemical investigation of the wood from Zanthoxylum quinduense Tul. allowed the isolation and identification of norchelerythrine, decarine, 6-acetonyldihydrochelerythrine, syringaresinol, evofilin C, p-hydroxybenzaldehyde, vanillic acid, a mixture of β-sitosterol, stigmasterol and campesterol and a mixture of saturated and unsaturated fatty acids, and their esters derivatives. The structures of the isolated compounds were elucidated by spectroscopic techniques and comparison with literature data and the mixture of sterols and fatty acids were identified by GC/MS. The antifungal activity of the ethanolic extract, fractions and pure compounds against Fusarium oxysporum f. sp. lycopersici was determined by bioautography. Evofilin C and nochelerytrine were the only substances that present antifungal activity.

Utilização de argilas para purificação de biodiesel

This work describes the results of the purification of methyl biodiesel, obtained by oxidized soybean oil, using different methods. After the ester separation from the glycerin by decanting, the ester was purified each time with distillation, washing with water and adsorption with bauxite, bentonite and attapulgite. The removal of total contamination, unsaponifiable material, concentrations of free glycerin and soap were analyzed in the purified ester phase. The best result of purification was observed with the use of bentonite and bauxite, in the removal of soap and free glycerin respectively.

Pré-concentração de Cr(III) e análise de especiação de cromo empregando montmorilonita saturada com íons potássio

The clay mineral montmorillonite-K10 (MT), treated under acidic medium and saturated with potassium ions (MTK), was employed in sorption and desorption studies aiming the preconcentration of Cr(III) and the speciation analysis of chromium. The sorption process of Cr(III) was close to 100%, suggesting that MTK was a good material for Cr(III) preconcentration, although, the maximum recovery in HNO3 solution was near 89%. On the other hand, Cr(VI) practically was not retained in MTK, suggesting this material as an appropriate mineral phase to be used in speciation analysis of chromium in aqueous medium.

Adsorção do corante azul de metileno em partículas de argilominerais: análise dos tamanhos das partículas

Interactions of cationic dye methylene blue (MB) with clay particles in aqueous suspension have been extensively studied. As already known, the number of natural negative charges on the clay modifies significantly the particle sizes dispersed in water and therefore the nature of the interaction with the dye. This work evaluated with UV-Vis spectroscopy method how the clay particle sizes weighted on the adsorption and rearrangement of the dye molecules in aqueous system. The results obtained from light-scattering measurements confirmed that larger particles are found in suspensions containing the high-charged clays as the visible absorption band related to the MB aggregates (570 nm) on these suspensions prevailed.

Metodologias para reutilização do resíduo de terra diatomácea, proveniente da filtração e clarificação da cerveja

The earth diatomite is a material used by the industries in the filtration process and clarification of the beer. This material presents a reduced useful life due to the blockages of their pores during the filtration process. The objective of this work was to reactivate the properties of filtration of the earth diatomite, saturated with organic matter during the filtration stage, starting from a controlled thermal treatment. The obtained results demonstrated that the earth diatomite saturated with organic matter submitted to a controlled thermal treatment has their filtration properties reactivated, could be reused in the beer production process.

Pyrrolizidine alkaloids of senecio sp from Peru

Six pyrrolizidine alkaloids (PAs) (two saturated macrocyclic, three unsaturated macrocyclic and one unsaturated seco-macrocyclic) were isolated from native Peruvian Senecio species. The structures of these alkaloids were established by a complete NMR spectroscopic analysis, chemical transformations and comparison of their NMR data with those published for similar alkaloids. Three PAs were then tested for antifungal activity against Fusarium moniliforme, F. (Sheldon), F. oxysporum fs. lycopersici (Scheldt) and F. solani (Mart), no significant activity being observed.

Síntese e caracterização de argilas organofílicas contendo diferentes teores do surfactante catiônico brometo de hexadeciltrimetilamônio

The major applications of organoclays are in adsorption of organic polluents. The objective of this work was the synthesis and characterization of organoclays using differents amounts of cationic surfactant hexadecyltrimethylammonium bromide. The clays were characterized by low angle x-ray diffraction (XRD), scanning electron microscope (SEM), infrared with Fourier tranformation (FTIR), BET surface area, elemental analysis (CHN), Foster swell and adsorption of methylene blue. The surfactant can adsorb in differents forms in the interlamelar region changed the basal spacing. The presence of the surfactant adsorbed can be favorable or not in adsorption of the methylene blue due the different interactions dye-organoclays.

Avaliação geoquímica de óleos brasileiros com ênfase nos hidrocarbonetos aromáticos

Aromatic compounds are still poorly evaluated in geochemical studies of Brazilian oil samples. For this reason, the objective of this work was to analyze and evaluate 26 oil samples from four Brazilian sedimentary basins. Aromatic hydrocarbon fractions have been analyzed by gas chromatography coupled to mass spectrometry. The results were also compared with previously evaluated saturated hydrocarbon data. Maturation parameters obtained using the 4- and 1-methyl-dibenzothiophenes and trimethyl-dibenzothiophenes led to the best results because a better grouping was observed. For this correlation, the samples were grouped by maturity degree enabling the routine use of these parameters to evaluate oil maturity levels.

Estudo teórico e experimental de espectros infravermelho de ésteres de ácido graxo presentes na composição do biodiesel de soja

In this work, theoretical and experimental infrared spectra of fatty acid methyl esters (FAME) contained in soybean biodiesel were analyzed seeking the assignments of the relevant vibrational modes to characterize crude soybean oil and soybean biodiesel. The results showed the usefulness of infrared spectra for monitoring saturated and unsaturated compounds as well as impurities (mainly glycerol) in raw samples. This is the first step toward proposing an efficient molecular spectroscopy routine to certify biodiesel fuel.

Desenvolvimento sustentável e pensamento complexo: estudo de caso: o uso de argilas como catalisadores

Use of clays as catalyzers in heterogeneous processes has increased significantly given their low cost, safety and commercial availability. However, interconnected political, economic, social, environmental, geological, and chemical aspects should be considered for chemical processes to satisfy sustainable development concepts. This concept requires complex thinking involving different areas of knowledge in dialogue, contrasting with classical thought, which is linear and Cartesian. Thus, this paper discusses the principles of complex thought in the concept of sustainable development exemplified by use of clay as a clean technology in organic synthesis.

Caracterização de resíduo sólido formado em biodiesel de sebo bovino

The nature of the solid residue formed in beef tallow biodiesel from two commercial producers in Brazil was determined by comparative analytical techniques, namely, gas chromatography with flame ionization detector (GC-FID) and thermogravimetry (TG). Pure monopalmitin and monostearin were used as reference standards for both methodologies. Analyses were carried out before and after filtration of the solids formed, which allowed the observation that the formation of precipitate reduced the levels of monoglycerides in the beef tallow biodiesel. The chromatographic and thermogravimetric results confirmed the nature of the residue as saturated monoglycerides, predominantly monostearin and monopalmitin.

Avaliação da potencialidade de microalgas dulcícolas como fonte de matéria-prima graxa para a produção de biodiesel

In this work, the fatty acid quantity and composition of six freshwater microalgae and soybean grains was determined by direct transesterification and gas chromatography analysis. The results showed that all the freshwater microalgae species presented a higher quantity of fatty acid than soybean grain. Choricystis sp. (A) provides 115% more fatty acids per gram of biomass than soybean grain. With regard to the fatty acid composition, Choricystis sp. (A) showed an adequate proportion of saturated and unsaturated fatty acids, with lower quantity of polyunsaturated fatty acids and, akin to some marine microalgae, constitutes an alternative raw material for biodiesel production.

Análise exploratória rápida e não destrutiva (screening) da presença de elementos químicos tóxicos em material escolar por fluorescência de raios x

Compulsory in Brazil, toy certification aims to prevent possible risks in toy use. The Brazilian National Institute of Metrology (INMETRO) establishes the maximum concentration of toxic elements (TE) that may be present in toys. This study evaluates the presence of TE in different crayons, gouache and modeling clays using X-ray fluorescence. This technique is fast, has low operating cost and minimum sample pretreatment, resulting in a clean procedure without reagent consumption and waste generation. Bromine (in gouache) and Barium (in crayons) were the only potentially TE identified in the samples studied.

Desenvolvimento de um método analítico baseado em microextração líquido-líquido para a determinação de cromo (VI) em amostras aquosas com detecção por espectrometria de absorção atômica em chama

In this study, a method for determination of hexavalent chromium in aqueous samples using liquid-liquid microextraction (LLME) and detection by Flame Atomic Absorption Spectrometry (F AAS) was developed. The LLME procedure was based on the extraction of Cr (VI) by acetone at a sample pH of 1.2. The use of saturated ammonium sulphate solution allowed effective separation of the aqueous and organic phases and acetone extracted chromium. The sample pH, acetone volume and stirring time were optimized by a full factorial design.