992 resultados para cation exchange capacity (CEC)


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This paper presents the results of a new investigation of the Guarani Aquifer System (SAG) in Sao Paulo state. New data were acquired about sedimentary framework, flow pattern, and hydrogeochemistry. The flow direction in the north of the state is towards the southwest and not towards the west as expected previously. This is linked to the absence of SAG outcrop in the northeast of Sao Paulo state. Both the underlying Piramboia Formation and the overlying Botucatu Formation possess high porosity (18.9% and 19.5%, respectively), which was not modified significantly by diagenetic changes. Investigation of sediments confirmed a zone of chalcedony cement close to the SAG outcrop and a zone of calcite cement in the deep confined zone. The main events in the SAG post-sedimentary history were: (1) adhesion of ferrugineous coatings on grains, (2) infiltration of clays in eodiagenetic stage, (3) regeneration of coatings with formation of smectites, (4) authigenic overgrowth of quartz and K-feldspar in advanced eodiagenetic stage, (5) bitumen cementation of Piramboia Formation in mesodiagenetic stage, (6) cementation by calcite in mesodiagenetic and telodiagenetic stages in Piramboia Formation, (7) formation of secondary porosity by dissolution of unstable minerals after appearance of hydraulic gradient and penetration of the meteoric water caused by the uplift of the Serra do Mar coastal range in the Late Cretaceous, (8) authigenesis of kaolinite and amorphous silica in unconfined zone of the SAG and cation exchange coupled with the dissolution of calcite at the transition between unconfined and confined zone, and (9) authigenesis of analcime in the confined SAG zone. The last two processes are still under operation. The deep zone of the SAG comprises an alkaline pH, Na-HCO(3) groundwater type with old water and enriched delta(13)C values (<-3.9), which evolved from a neutral pH, Ca-HCO(3) groundwater type with young water and depleted delta(13)C values (>-18.8) close to the SAG outcrop. This is consistent with a conceptual geochemical model of the SAG, suggesting dissolution of calcite driven by cation exchange, which occurs at a relatively narrow front recently moving downgradient at much slower rate compared to groundwater flow. More depleted values of delta(18)O in the deep confined zone close to the Parana River compared to values of relative recent recharged water indicate recharge occur during a period of cold climate. The SAG is a ""storage-dominated"" type of aquifer which has to be managed properly to avoid its overexploitation. (C) 2011 Elsevier Ltd. All rights reserved.

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In this paper, we study the influence of the National Telecom Business Volume by the data in 2008 that have been published in China Statistical Yearbook of Statistics. We illustrate the procedure of modeling “National Telecom Business Volume” on the following eight variables, GDP, Consumption Levels, Retail Sales of Social Consumer Goods Total Renovation Investment, the Local Telephone Exchange Capacity, Mobile Telephone Exchange Capacity, Mobile Phone End Users, and the Local Telephone End Users. The testing of heteroscedasticity and multicollinearity for model evaluation is included. We also consider AIC and BIC criterion to select independent variables, and conclude the result of the factors which are the optimal regression model for the amount of telecommunications business and the relation between independent variables and dependent variable. Based on the final results, we propose several recommendations about how to improve telecommunication services and promote the economic development.

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A retenção de Se pelos colóides do solo constitui importante processo para a manutenção da sanidade ambiental. A informação sobre a adsorção de Se em solos altamente intemperizados é restrita e existem poucos padrões quantitativos disponíveis para a definição de estratégias de remediação de áreas contaminadas. Quantidades crescentes de Se (5, 10, 25, 50, 100 e 250 mg L-1), na forma de Na2SeO3, foram adicionadas a amostras de dez Latossolos brasileiros [três Latossolos Vermelho-Amarelos (LVA-1, LVA-2 e LVA-3), dois Latossolos Vermelhos (LV-1 e LV-2), um Latossolo Vermelho eutroférrico (LVef), um Latossolo Vermelho acriférrico (LVwf), dois Latossolos Amarelos (LA-1 e LA-2) e um Latossolo Amarelo acriférrico (LAwf)]. Isotermas de adsorção foram construídas e foi verificado o ajuste dos resultados experimentais aos modelos de Langmuir e de Freundlich. A equação de Langmuir ajustou melhor os resultados de adsorção de Se do que a isoterma de Freundlich. Todas as isotermas apresentaram o formato tipo-L (exponencial), com exceção daquelas obtidas para o LVA-1 e para o LVA-2, que apresentaram comportamento tipo-C (linear). Valores de adsorção máxima (Ads máx), estimada pelo modelo de Langmuir, variaram de 135 (LVA-3) a 2.245 mg kg-1 (LA-1), enquanto os coeficientes de afinidade (K L) estiveram entre 0,002 (LVA-2) e 0,326 (LVA-3). A constante de afinidade estimada pelo modelo de Freundlich (Kf) variou de 13,7 (LVA-2) a 180,1 (LAwf). A adsorção máxima de Se foi mais elevada no LVef e nos Latossolos ácricos (LAwf e LVwf), enquanto os maiores valores de Kf foram encontrados no LV-2, LVef, LVA-3 e LVwf. Não houve correlação entre os atributos dos solos e as constantes de Langmuir. Valores de Kf correlacionaram-se com os teores de argila (r = 0,42*) e com a capacidade de troca de ânions (r = 0,64*).

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O objetivo deste trabalho foi avaliar possíveis efeitos da aplicação de taxas de água residuária de suinocultura (ARS), quanto às concentrações de cobre e zinco, tanto no solo quanto na água percolada de lisímetros de drenagem, durante o ciclo da cultura da soja. O experimento foi conduzido em ambiente protegido, onde havia 24 lisímetros de drenagem. Semeou-se soja cultivar CD 202, e foram aplicadas ARS nas seguintes dosagens: 0; 100; 200 e 300 m³ ha-1 no ciclo, combinadas com duas adubações na semeadura (com e sem adição da adubação recomendada na semeadura), em três repetições por tratamento. Foram feitas seis coletas do material percolado durante o ciclo da cultura e realizadas determinações de cobre e zinco. No solo, foram feitas três coletas em cada parcela experimental, para a determinação do pH, da matéria orgânica, da capacidade de troca catiônica, do cobre e do zinco. O delineamento foi em blocos casualizados, num esquema fatorial de 4 x 2. Observou-se que o cobre no solo não apresentou diferenças significativas com a aplicação de ARS e adubação, enquanto as concentrações de zinco no solo foram influenciadas pelas taxas aplicadas de ARS. As transferências de cobre e de zinco por percolação foram pouco expressivas.

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Actually, surveys have been developed for obtaining new materials and methodologies that aim to minimize environmental problems due to discharges of industrial effluents contaminated with heavy metals. The adsorption has been used as an alternative technology effectively, economically viable and potentially important for the reduction of metals, especially when using natural adsorbents such as certain types of clay. Chitosan, a polymer of natural origin, present in the shells of crustaceans and insects, has also been used for this purpose. Among the clays, vermiculite is distinguished by its good ion exchange capacity and in its expanded form enhances its properties by greatly increasing its specific surface. This study aimed to evaluate the functionality of the hybrid material obtained through the modification of expanded vermiculite with chitosan in the removal of lead ions (II) in aqueous solution. The material was characterized by infrared spectroscopy (IR) in order to evaluate the efficiency of modification of matrix, the vermiculite, the organic material, chitosan. The thermal stability of the material and the ratio clay / polymer was evaluated by thermogravimetry. To evaluate the surface of the material was used in scanning electron microscopy (SEM) and (BET). The BET analysis revealed a significant increase in surface area of vermiculite that after interaction with chitosan, was obtained a value of 21, 6156 m2 / g. Adsorption tests were performed according to the particle size, concentration and time. The results show that the capacity of removal of ions through the vermiculite was on average 88.4% for lead in concentrations ranging from 20-200 mg / L and 64.2% in the concentration range of 1000 mg / L. Regarding the particle size, there was an increase in adsorption with decreasing particle size. In fuction to the time of contact, was observed adsorption equilibrium in 60 minutes with adsorption capacity. The data of the isotherms were fitted to equation Freundlich. The kinetic study of adsorption showed that the pseudo second- order model best describes the adsorption adsorption, having been found following values K2=0,024 g. mg-1 min-1and Qmax=25,75 mg/g, value very close to the calculated Qe = 26.31 mg / g. From the results we can conclude that the material can be used in wastewater treatment systems as a source of metal ions adsorbent due to its high adsorption capacity

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Among the various layered silicates, vermiculite has been used as one of the adsorbent material by presenting the ion exchange capacity which facilitates the removal of organic compounds which are potential pollutants in relation to the water surface. The importance of the modification of clay minerals by hydrophobization with carnauba wax establishes the increase in oil removal capacity in aqueous medium, it contributes to a better environment for life in ecosystems. The vermiculite when expanded decreases its hydrophobicity requiring the use of a hydrophobizing leaving - the organoclay. In this work were used in the process of modifying the particle sizes of vermiculite -18+16, -16 +20 and -20 +35 #. Samples of vermiculite hydrophobized with carnauba wax and clay mineral without hydrophobizing were characterized with physicochemical analyzes and analytical. Techniques were used: thermal analysis (thermogravimetry and derivative thermogravimetry), infrared spectroscopy, scanning electron microscopy, fluorescence rays - x adsorption tests. The TG / DTG was used to evaluate the thermal behavior of expanded vermiculite and carnauba wax and samples hidrofobizadas with percentages of 5, 10 and 15 % by weight of hydrophobizing. The results of FTIR confirmed increase of the characteristic signs of carnauba wax in samples hidrofobizadas as the greatest amount of hydrophobizing the clay mineral used in hydrophobization. Thermogravimetry and FTIR show based on the results that coating the surface of the vermiculite occur homogeneously. The data obtained by the technique of x-ray fluorescence with loss on ignition confirmed the results of thermogravimetric analysis in relation to the percentage of wax incorporated. The fluorescence indicates through information provided by the analysis shows that the material covered - is homogeneous. The mev inspection was used to texture and morphology of the clay mineral with and without carnauba wax. The scanning electron microscopy confirms the deposition of wax evenly over the surface of the mineral as indicated by the other techniques. To verify the adsorption capacity of the clay without hydrophobizing hydrophobized and used a fixed volume of water to 1 ½ liters in each experiment with 3 g to 50 g of oil sample. The results show that better extraction of oil for the material processed corresponds to 260 % relative to the weight of the sample coated and greater than 80 % of the oil drop in the system

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The biochemical and functional characterization of wasp venom toxins is an important prerequisite for the development of new tools both for the therapy of the toxic reactions due to envenomation caused by multiple stinging accidents and also for the diagnosis and therapy of allergic reactions caused by this type of venom. PLA(1) was purified from the venom of the neotropical social wasp Polybia paulista by using molecular exclusion and cation exchange chromatographies; its amino acid sequence was determined by using automated Edman degradation and compared to the sequences of other vespid venom PLA(1)'s. The enzyme exists as a 33,961.40 da protein, which was identified as a lipase of the GX class, liprotein lipase superfamily, pancreatic lipases (ab20.3) homologous family and RP2 sub-group of phospholipase. P. paulista PLA(1) is 53-82% identical to the phospholipases from wasp species from Northern Hemisphere. The use restrained-based modeling permitted to describe the 3-D structure of the enzyme, revealing that its molecule presents 23% alpha-helix, 28% beta-sheet and 49% coil. The protein structure has the alpha/beta fold common to many lipases; the core consists of a tightly packed beta-sheet constituted of six-stranded parallel and one anti-parallel beta-strand, surrounded by four alpha-helices. P. paulista PLA(1) exhibits direct hemolytic action against washed red blood cells with activity similar to the Cobra cardiotoxin from Naja naja atra. In addition to this, PLA(1) was immunoreactive to specific IgE from the sera of P. paulista-sensitive patients. (c) 2007 Elsevier Ltd. All rights reserved.

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A series of studies was conducted to establish a methodology for the accurate and efficient determination of betaine in different feed ingredients. The final methodology involves an extraction step in which the feed sample is heated for 3h in a methanolic KOH solution using a Goldfisch apparatus. Impurities are removed by the addition of activated charcoal and concentrated (36%) HCl. After centrifugation the extractant is passed through a strong cation exchange resin (Dowex 50W-X12, H+). The betaine retained in the column is eluted with 1.5 N HCl. A 2 nil aliquot of the elute is air dried and reconstituted with 1 ml of deionised water. HPLC separation with a cation exchange column (Partisil SCX-10) is used for the separation of betaine from other compounds. The mobile phase is kept constant at 50mm KH2PO4 in water, and eluted compounds are detected by UV absorbance (200nm). The flow rate is maintained at 1.5ml min(-1). This assay is very accurate over the range of betaine concentrations from 15 to 650 mug ml(-1), with a lower detection limit in feeds of approximately 500 mug g(-1) when 4g of sample is extracted. Recovery assays done with standard betaine hydrochloride and hard red wheat resulted in a consistent recovery of 80%. Betaine content was quantified in several feed ingredients, including alfalfa (1.77 mg kg(-1)), wheat (3.96 mg kg(-1)), wheat middlings (4.98 mg kg(-1)) and poultry meal (0.77 mg kg(-1)). Betaine in corn and soybean meal was not detectable by this method, even when 16g of sample was used (<125 mg kg(-1)). Betaine present in several feed ingredients should influence choline supplementation to animal feeds and may have implications for human health. (C) 2002 Society of Chemical Industry.

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Titanium(IV) oxide, coated on the surface of silica gel (surface area, 308 m2 g-1; amount of Ti(IV) per gram of modified silica gel, 1.8 x 10(-3) mol), was used to adsorb CrO4(2-) ions from acidic solutions. The exchange capacity increased at lower pH values and was affected to some extent by the acid used. The material was used to preconcentrate Cr(VI) from 0.5 ppm solutions of chromate very efficiently and virtually 100% recovery was achieved in every instance.

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SnO2 supported membranes, presenting 3.0 nm average pore size, have been produced by sol casting on alumina tubular substrate using aqueous colloidal suspensions prepared by sol-gel route. The selectivity and flux throughout SnO2 membrane were analyzed by permeation experiments, using a laboratory tangential filtration pilot equipped with a monotubular membrane. To evaluate the effect of the surface charge at the membrane-solution interface, aqueous salt solutions (NaCl, Na2SO4, CaCl, and CaSO4) of different ionic strength have been filtered and the results correlated with the values of zeta potential measured at several pH. The results show that the retention coefficient is dependent on the electrolyte present in aqueous solution decreasing as: (dication, monoanion) > (monocation, monoanion) approximate to (monocation, dianion) > (dication, dianion). The surface charge and the cation adsorption capacity play a determinant role in these selectivity sequences. (C) 2001 Elsevier B.V. B.V. All rights reserved.

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The high rate of mineralization of organic matter on savannah soils, which is reached fi ve times faster than in temperate regions, leads us to the challenge of electing the best system of management that maintains and/or increase it in soil, guaranteeing its quality and sustainability. In this sense the present research aimed to study the effects of green, organic and mineral manure on the chemical properties on the chemical properties of an Oxisol, on Savannah area, cultivated with cotton (Gossypium hirsutum) under conventional tillage and no-tillage in the pasture fi eld (Brachiaria decumbens) for 20 years. The experimental design was a randomized block design with split plots. The main plots consisted of two treatments: conventional tillage and no-tillage, and the subplots of six treatments: control (no fertilizer), mineral fertilizer recommended for the crop, according to the soil chemical analysis, organic fertilizer (cattle manure - 20 t ha-1), organic fertilizer (cattle manure - 20 t ha-1) + 1/2mineral fertilization recommended according to the analysis of soil, green manure-1 (Crotalaria juncea) and green manure-2 (Pennisetum americanum). There were studied the following soil chemical properties: P, OM, pH, K, Ca, Mg, Al, Al + H, S, exchange capacity cations and base saturation. The soil samples for the analysis were performed on layers of 0,00-0,05 m, 0,05-0,10 and 0,10-0,20 m. Then it came the following conclusions: the fertilization interfere in soil chemical properties and the preparation did not interfere, the cattle manure and its association with the mineral fertilizer caused increasing level elements in the soil, Crotalaria juncea and Pennisetum americanum did not infl uence on soil chemical properties.

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)