Composição química de um resíduo alcalino da indústria de papel e celulose (DREGS)

Dregs is an alkaline solid by-product generated in the cellulose manufacturing industry that could be used to correct soil acidity. The present study aimed to evaluate the chemical composition of this product and some of its properties. The dregs presented 354 g kg-1 of calcium, neutralization capacity of 80.3%, and pH 10.7, besides low concentration of sodium (10.2 g kg-1), lead (62.9 mg kg-1) and cadmium (5.6 mg kg-1). Thus, it is a product that can safely be used to increase the soil pH.

Determinação voltamétrica por redissolução anódica de Cu(II) em águas residuárias empregando um eletrodo de pasta de carbono modificado com quitosana

The electrochemical applications of a CPE modified with chitosan for the determination of Cu(II) in wastewater samples using anodic stripping voltammetry are described. The best voltammetric response was observed for a paste containing 25% m/m of chitosan. A 0.10 mol L-1 NaNO3 solution (pH 6.5) as supporting electrolyte, a pre-concentration potential of -0.20 V, pre-concentration time of 270 s and a scan rate of 25 mV s-1 were selected. The calibration graph was linear in the Cu(II) concentration range from 2.0 x 10-7 to 7.4 x 10-6 mol L-1, with a detection limit of 8.3 x 10-8 mol L-1.

Funcionalização de nanotubos de Carbono

Carbon nanotubes are very stable systems having considerable chemical inertness due to the strong covalent bonds of the carbon atoms on the nanotube surface. Many applications of carbon nanotubes require their chemical modification in order to tune/control their physico-chemical properties. One way of achieving this control is carrying out functionalization processes where atoms and molecules interact (covalent or non-covalent) with the nanotubes. We review some of the progress that has been made in chemical functionalization of carbon nanotubes. Emphasis is given to chemical strategies, the most used techniques, and applications.

Composição química e atividade biológica das folhas e frutos de Triphasia trifolia

The chemical composition of the essential oils from leaves and fruits of Triphasia trifolia was analyzed by GC-FID and GC-MS. The major constituents of oil obtained from leaves were sabinene (35.4%) and myrcene (34.1%), while the prevalent compounds in oil from fruits were sabinene (37.2%), beta-pinene (23.95) and gamma-terpinene (16.3%). Both oils showed moderate antimicrobial activity. The fruit decoction was also investigated leading to the isolation of the coumarins isopimpinelin, (R)-byakangelicin and (S)-mexoticin. From leaves were isolated the coumarins (R)-byakangelicin, aurapten, (S)-mexoticin, isosibiricin, isomerazin and coumurrayin and the flavonoid vitexin. All coumarins showed cholinesterase inhibition on TLC tests.

Estudo comparativo de métodos para a determinação da concentração de carbono em solos com altos teores de Fe (Latossolos)

Soil organic matter (SOM) plays an important role in physical, chemical and biological properties of soil. Therefore, the amount of SOM is important for soil management for sustainable agriculture. The objective of this work was to evaluate the amount of SOM in oxisols by different methods and compare them, using principal component analysis, regarding their limitations. The methods used in this work were Walkley-Black, elemental analysis, total organic carbon (TOC) and thermogravimetry. According to our results, TOC and elemental analysis were the most satisfactory methods for carbon quantification, due to their better accuracy and reproducibility.

Lipídios estruturados obtidos a partir da mistura de gordura de frango, sua estearina e triacilgliceróis de cadeia média: I- Composição em ácidos graxos e em triacilgliceróis

The purpose of this study is to analyze the interactions that occur in binary and ternary fat blends between medium and long chain triacylglycerols and their structured lipids obtained by chemical interesterification through the analysis of their physico-chemical properties. The synthesized structured triacylglycerols presented from 14.8 to 58.4% medium chain fatty acids, from 15.7 to 37.2% saturated fatty acids, from 19.2 to 47.5% monounsaturated fatty acids, and from 6.7 to 15.2% essential fatty acids. Chemical interesterification modified the behavior of binary and ternary mixtures and new types of triacylglycerol groups were formed.

Síntese de padrões cromatográficos e estabelecimento de método para dosagem da composição de ésteres de ácidos graxos presentes no biodiesel a partir do óleo de babaçu

Several alkyl esters were synthesized, purified, characterized by ¹H NMR and employed as standards for establishing chromatographic methods to monitor their formation in the synthesis of biodiesel. The efficiency of the chromatographic methods was confirmed with the products of enzymatic transesterification of babassu oil with different alcohols (C2 to C4), using Lipozyme as catalyst.

Influência da temperatura de secagem sobre o rendimento e a composição química do óleo essencial de Tanaecium nocturnum (barb. Rodr.) bur. & K. Shum

The yields and chemical compositions of the essential oils obtained by steam distillation of the fresh and dried (30 and 40 ºC) leaves, stems and roots of Tanaecium nocturnum are reported. The identification and quantification of the volatile constituents were accomplished by GC/MS and GC/FID, respectively. The essential oils obtained from the various parts of the plant were constituted mainly of benzaldehyde. Large losses and variations in the quantities of the components during the drying process were observed. The presence of mandelonitrile in higher concentration in the stem and roots indicates that this species produces cyanogenic glycosides.

Avaliação da composição química de fermentados alcoólicos de jabuticaba (myrciaria jabuticaba)

This work aimed to characterize the chemical composition of samples of alcoholic beverages fermented from jabuticaba produced in five successive crops. Up to 2005 most of the results didn't meet the current legal standards for wines and there was a negative correlation between parameters such as pH and volatile acidity, pH and total acidity, volatile acidity and alcohol content (p<0.01). The implementation of Good Manufacturing Practices and must sulfitation during the 2006 harvest lowered volatile acidity and more than 60% of the samples were in accordance with legislation. Also, a significant improvement in alcohol content was found (p<0.05)

Composição química dos óleos essenciais das folhas de seis espécies do gênero Baccharis de "Campos de Altitude" da mata atlântica paulista

The essential oils from the leaves of six species of the Baccharis genus (B. dracunculifolia, B. microdonta, B. regnelli, B. schultzii, B. trimera, and B. uncinella), collected in the "Campos de Altitude" of the Atlantic Forest (SP), were extracted using hydrodistillation procedures and analyzed by GC and GC/MS. There was a predominance of sesquiterpenes in all studied oils as b-elemene in B. dracunculifolia and B. regnelli, a-humulene in B. trimera, g-gurjunene in B. schultzii, bicyclogermacrene in B. regnelli, d-cadinene in B. regnelli and B. uncinella, spathulenol in B. schultzii, caryophyllene oxide in B. microdonta and guaiol in B. uncinella. However, a high amount of monoterpenes was also observed in B. uncinella (a-pinene), B. regnelli (d-car-3-ene) and B. schultzii (limonene). The chemical compounds of the essential oils of B. schultzii, B. regnelli and B. microdonta are described for the first time in this work.

Bioprocessos para remoção de dióxido de carbono e óxido de nitrogênio por micro-algas visando a utilização de gases gerados durante a combustão do carvão

The aim of this work was to study the removal of CO2 and NO by microalgae and to evaluate the kinetic characteristics of the cultures. Spirulina sp. showed µmax and Xmax (0.11 d-1, 1.11 g L-1 d-1) when treated with CO2 and NaNO3. The maximum CO2 removal was 22.97% for S. obliquus treated with KNO3 and atmospheric CO2. The S. obliquus showed maximum NO removal (21.30%) when treated with NO and CO2. Coupling the cultivation of these microalgae with the removal of CO2 and NO has the potential not only to reduce the costs of culture media but also to offset carbon and nitrogen emissions.

Composição e atividade antibacteriana dos óleos essenciais de Senecio crassiflorus var. crassiflorus

The essential oils of leaves, aerial and underground stems of Senecio crassiflorus var. crassiflorus were extracted by hydrodistillation and their analyses were performed by GC/MS. Qualitative and quantitative differences have been found between the analyzed parts. The main compounds of the essentials oils of the leaves were found to be oxygenated sesquiterpenes, while the oils from the aerial and underground stems showed sesquiterpene hydrocarbons as major constituents. Furthermore, the essential oils were tested against Staphylocccus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus. The essential oil of the leaves was shown to be the most active.

Otimização da análise isotópica de UF6 utilizando-se a técnica de espectrometria de massas por quadrupolo

A procedure for determining of the isotope ratio 235U/238U in UF6 samples was established using a quadrupole mass spectrometer with ionization by electron impact. The following items were optimized in the spectrometer: the parameters in the ion source that provided the most intense peak, with good shape, for the most abundant isotope; the resolution that reduced the non linear effects and the number of analytical cycles that reduced the uncertainty in the results. The measurement process was characterized with respect to the effects of mass discrimination, linearity and memory effect.

Conteúdo lipídico e composição de ácidos graxos de microalgas expostas aos gases CO2, SO2 e NO

The objective of the present work was to verify the lipid content and the fatty acid composition of the microalgae Spirulina sp., Scenedesmus obliquus, Synechococcus nidulans and Chlorella vulgaris cultivated in a medium containing CO2, SO2 and NO. The microalga Scenedesmus obliquus presented the highest lipid content (6.18%). For the other microalgae the lipid content ranged from 4.56 to 5.97%. The major monounsaturated fatty acids content was 66.01% for S. obliquus. The PUFA were obtained in major amount by the microalgae Spirulina sp. (29.37%) and S. nidulans (29.54%). The palmitoleic acid was in larger amount, with 41.02% concentration (Spirulina sp.).

Avaliação do efeito da concentração de carbonato na eletrodeposição de cobre sobre discos de aço-carbono

Mild steel blankets were covered with electrolytic copper thin layer, from cyanide bath, being evaluated the influence of the carbonate concentration in the physiochemical properties of those deposits. The cell voltage decreased as the current intensity decreased, but the adherence of the deposit was not enhanced, showing that the increment of carbonate concentration causes substantial problems. Chemical solubilization reactions of air-bearing carbon dioxide and oxidation of free cyanide ions through dissolved oxygen evolved in the anodic processes contribute to the copper plating to occur in an inefficient way. The best optimal conditions require a carbonate concentration below 50 g L-1.