Iron oxides in plinthic soils on sedimentary deposits in northeastern Brazil

This study was conducted to examine the distribution and nature of Fe oxides in plinthic soils on the sediments of Barreiras Group (in the state of Piauí) and Itapecuru Formation (in the state of Maranhão) in Northeastern Brazil. Four pedons were selected: a "plinthic, dystrophic, epieutrophic Gray Podzolic with low activity clay" and a "dystrophic Plinthosol with low activity clay" (both Plinthic Kandiustalfs) on the Barreiras sediments, as well as an "eutrophic Plinthosol with low activity clay" and an "allic Plinthosol with low activity clay" (both Plinthustalfs) on the Itapecuru sediments. Soil samples were fractionated into > 2 mm (pisoliths), water-stable aggregates (plinthite) and matrices; the aggregates and matrices were further fractionated into sand, silt and clay sizes. Dithionite extractable iron (Fe d) and aluminum (Al d), as well as oxalate extractable iron (Fe o), were determined for all fractions, and X-ray diffraction analyses were performed on the pisoliths. It was observed that the Plinthustalfs contain more iron oxides, exhibit more extensive plinthite development and have a greater potential for further plinthite development than the Kandiustalfs. The distribution of values for the Fe d indicates that plinthite formation and induration in all soils were accompanied by an enrichment of Fe oxides in all particle size fractions. This Fe segregation was accompanied by aggregation of particles leading to a greater degree of crystallinity, as indicated by analysis of the ratios of Al d:Fe d. Larger ratios of goethite to hematite, and relatively smaller amounts of silicates in the more mature pisoliths were revealed by X-ray diffraction analysis. Ratios of Al d:Fe d were larger in the Kandiustalfs than in the Plinthustalfs, and also larger than expected for Al-substituted Fe oxides. According to ratios of Al d:Fe d, Fe mobilization in all soils has likely occurred under reducing conditions, facilitated by organic matter on the soil surface.

Chemical properties and mineralogy of soils with plinthite and petroplinthite in Iranduba (AM), Brazil

Large areas of Plinthosols with ferruginous materials such as plinthite and/or petroplinthite are fairly common in the Brazilian Amazon basin. This work was carried out to investigate the chemical behavior, mineralogical composition and weathering stage of four representative soil profiles with plinthite and petroplinthite, in Iranduba, AM (Central Amazon). Three well-drained soil profiles at high elevations were studied (P1, Plinthic Vetic Ferralsol; P2 and P3, Vetic Endopetric Plinthosol) and a contrasting poorly drained soil (P4 Haplic Plinthosol), located at low elevation. After profile descriptions, soil samples were collected from each horizon, air-dried, sieved (2 mm), and analyzed for particle-size distribution, pH, exchangeable cations (Al3+, Ca2+, Mg2+, K+, and Na+), as well as available P and total organic carbon (TOC) content. The minerals present in the clay and sand fractions, as well as in the ferruginous materials were identified by X-ray Diffraction (XRD). The weathering stage of these soils was assessed by means of Ki and Kr indexes, and the amounts of free and amorphous Fe and Al oxides by using dithionite citrate bicarbonate (DBC) and ammonium oxalate dissolution procedures, respectively. The results showed that all soils were extremely unfertile, with pH levels ranging between strong and moderate acidity, very low sum of bases and organic matter content, and of available P. The mineralogy of the soil profiles was very similar, mainly of the well-drained soils, with predominance of kaolinite and quartz in the clay and sand fractions, respectively. In the poorly-drained P4, 2:1 clay particles were also observed. These profiles can be considered highly developed according to the Ki index, however, the Ki value of P4 was higher, indicating that this soil was less developed than the others. In summary, these profiles with plinthite and petroplinthite can be characterized as highly developed and infertile soils and are, with exception of P4, well-drained.

Análise de suspensões de argilas por espectrometria de emissão óptica com plasma induzido com configuração axial

The goal of this study was to evaluate the feasibility of direct introduction of clay slurries in an inductively coupled plasma optical emission spectrometer with axial view configuration. Calibration was performed using a certified reference material with a mean particle size of 13 µm (IPT-42) and the analytical curve was applied for quantification of two others reference materials (IPT-28 and IPT-32) and four samples. It was demonstrated that the analytical curve thus obtained was not completely suitable for IPT-28 and samples due to different mineralogical phases determined by X-ray diffraction. After considering this effect, it was possible for most elements to obtain results in agreement with certified values or with values obtained by a conventional technique at a 95% confidence level. It was demonstrated that the ICP-OES with axial view configuration did not present any incompatibility with the direct introduction of a complex inorganic suspension.

Determinação da humificação da matéria orgânica de um latossolo e de suas frações organo-minerais

Laser-induced fluorescence spectroscopy was used to determine the humification degree of the organic matter of a whole soil, that is, soil without any physical or chemical treatment. Particle size was determined in physically separated fractions. The humification of organic matter, the depth of the soil and the planting system can be correlated. On the surface of the soil, no tillage provided the smallest humification in comparison with the conventional tillage and reduced tillage. The fractions of the superficial layer of the soil (0-20 cm) indicated larger humification in the fraction from 20 to 53 µm and the smallest in the fraction of <2 µm.

Caracterização de cinza do bagaço de cana-de-açúcar para emprego como pozolana em materiais cimentícios

This work presents the results of morphological and physical-chemical characteristics of a sugar cane bagasse ash material sample produced under controlled burning conditions. The investigation was carried out by analyzing chemical composition, X-ray diffraction, 29Si nuclear magnetic resonance, morphology, thermal analysis, particle size, specific surface, and density. Moreover, the pozzolanic activity of the ash was evaluated by pozzolanic activity index and Chapelle's method. The results suggest that the sugar cane bagasse ash has adequate properties to be used as pozzolan in construction materials.

Remoção de compostos orgânicos em água empregando carvão ativado impregnado com óxido de ferro: ação combinada de adsorção e oxidação em presença de H2O2

In this work, composites based on activated carbon/iron oxide (AC/Fe) were prepared in two different proportions (AC/Fe 5/1 and 1/1) and evaluated in the removal of the organic dye methylene blue (MB). Physical-chemical properties of the composites were determined by X-ray diffraction (XRD), adsorption/dessorption of N2 isotherm, temperature programmed reduction (TPR) and scanning electron microscopy (SEM). Results showed that goethite (α- FeOOH), with nanometer particle size, was formed over carbon surface for both composites. These materials showed high efficiency to remove MB from solution by combined adsorption and oxidation process. The AC/Fe 1/1 showed to be more active in (MB) oxidation then AC/Fe 5/1.

Síntese e caracterização de nanopartículas de óxido de ferro suportadas em matriz carbonácea: remoção do corante orgânico azul de metileno em água

In this work were prepared composites of iron oxide and carbonaceous materials in two different weight proportions (Carbon/Fe 1/1 and 1/2). The physico-chemical properties of the composites were determined by temperature programmed reduction (TPR), adsorption/dessorption of N2, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and pulse titration H2. The XRD and XPS analysis showed a cubic iron oxide phase, identified as maghemite, formed over the carbon surface. The particle size of maghemite showed to be within 10-30 nm. Carbon/Fe 1/2 was the most active in MB removal kinetics and ESI-MS studies showed that MB removal by both composites leads to oxidized intermediates.

Processamento e caracterização de espumas vitrocerâmicas do sistema sncp (Sio2-Na2o-Cao-P2 O5)

Glass-ceramics foams prepared from glasses of the SiO2-Na2O-CaO-P2O5 by replication process were obtained and characterized in terms of their chemical and physical properties by X-ray fluorescence, X-ray diffraction, laser diffraction, thermal analysis, density, mechanical strength, microstructural and cytotoxic analysis. The results showed that it is possible to produce glass-ceramic foams by the replication method with optimized properties but cytotoxic analysis indicates that the glass-ceramic foams are not bioactive materials. Mechanical strength values varying from 0.5 to 1.0 MPa and from 0.8 to 2.3 MPa were reached for mean particle sizes of 10 and 6 µm, respectively.

Production of silica gel from residual rice husk ash

This paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. Measurements of the chemical composition, X-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. The compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. The results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.

Avaliação da porosidade de microcápsulas contendo proteína bioativa por porosimetria de mercúrio e adsorção de nitrogênio

Microcapsules containing lactoferrin were produced by spray drying using dextrin:octenylsuccinate starch, as wall materials. Porosity characteristics of spray-dried microcapsules were investigated by mercury intrusion porosimetry and nitrogen adsorption. The outer and inner structures of microcapsules were studied by Scanning Electron Microscopy and sizes were determined by Laser Diffraction. Results indicate that all microcapsules presents adsorption isotherm of type II and that micropores on the microcapsules surface will be very few or none. Our results show that microstructure, surface area and size of microcapsules are affected by dextrin: octenylsuccinate starch proportion. Pore characteristics for various microcapsules are found to be different.

A comparative study of hydroxyapatite nanoparticles synthesized by different routes

In this study, bioactive hydroxyapatite nanoparticles were prepared by two different methods: wet chemical precipitation and biomimetic precipitation. The aim was to evaluate the morphology, particle-size, crystallinity and phases of the powders obtained by traditional wet chemical precipitation and the novel biomimetic precipitation using a supersaturated calcium solution. The nanoparticles were investigated by transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results revealed that the nanoparticles were formed by hydroxyapatite with a high crystallinity and controlled morphology. Additionally, it was found that the shape and size of the nanoparticles can be modified with each preparation method.

Characterization and use of swine deep bedding ashes in cementitious composites

The deep bedding is a swine alternative production, especially in the finishing phase, whose byproduct can be recycled, reducing the environmental impact. The objectives of this study were to characterize the ash coming from the controlled burning of the swine deep bedding (SDBA) based on rice husk, and to evaluate their performance in composites as a partial substitute for Portland cement (PC). To measure the differences between SDBA and rice husk ash (RHA) as a reference, we have characterized: particle size distribution, real specific density, x-ray diffraction, electrical conductivity, scanning electron microscopy, chemical analysis and loss on ignition. Samples were prepared for two experimental series: control, and another one with the partial replacement of 30% of SDBA in relation to the mass of the Portland cement. According to the results obtained for physical and mechanical characterization, the composites with SDBA can be used as a constructive element in the rural construction.

Nutrient accumulation and biomass production of alfafa after soil amendment with silicates

Studies on the use of silicate correctives in agriculture show that they have great potential to improve soil chemical characteristics, however, little information is available on the reactivity rates of their particle-size fractions. This study investigated whether the reactivity rates obtained experimentally could be considered in the calculation of ECC (effective calcium carbonate) for soil liming, promoting adequate development of alfalfa plants. Six treatments were evaluated in the experiment, consisting of two slag types applied in two rates. The experimental ECC was used to calculate one of the rates and the ECC determined in the laboratory was used to calculate the other. Rates of limestone and wollastonite were based on the ECC determined in laboratory. The rates of each soil acidity corretive were calculated to increase the base saturation to 80%. The treatments were applied to a Rhodic Hapludox and an Alfisol Ferrudalfs. The methods for ECC determination established for lime can be applied to steel slag. The application of slag corrected soil acidity with consequent accumulation of Ca, P, and Si in alfalfa, favoring DM production.

Foregut morphology of Macrobrachium carcinus (Crustacea, Decapoda, Palaemonidae)

ABSTRACT Macrobrachium carcinus is a Brazilian native prawn with recognized potential for use in aquaculture activities. The aim of this study was to describe and illustrate in detail the morphology of the M. carcinus foregut. The foregut comprises the mouth, esophagus and stomach. It is lined by a simple cylindrical epithelium overlain by chitinous cuticle. The cardiac chamber is well supplied with muscles and lined with chitin thickened in places to form a complex, articulating set of ossicles. The ossicles and setae inside the cardiac chamber seem to direct the food movement through the cardiac chamber and sort the food according to particle size as digestion takes place. Twenty-one basic ossicles were observed in the stomach ofM. carcinus and are divided into seven categories, reflecting their presumed functional roles. The significance of these morphological features is discussed in terms of its implication in feeding management that can support future commercial farms of this important fishery resource.

Development of a Bacillus sphaericus tablet formulation and its evaluation as a larvicide in the biological control of Culex quinquefasciatus

This study aimed to analyze the final fermentation culture of Bacillus sphaericus 2362, standardize it and develop an active tablet formulation for use in urban mosquito breeding sites. It was performed in three phases: analysis and standardization of a B. sphaericus fermented culture; physical, chemical, and biological analysis of the active powder (solubility, residual humidity, particle size, resting angle, flowing off time, compacted density, and biological activity against Culex quinquefasciatus larvae); and the development of fast-disintegrating tablets. Five formulations with differing compositions were developed and a UV protector was added to the selected formulation. The formulation products with or without UV protector, as well as the active powder caused 100% larval mortality from 1 day to 2 months after a single treatment under simulated field conditions. These results show that the UV protector does not affect the initial larvicide activity of B. sphaericus, nor its persistence over a period of two months.