Biohydrometallurgical/UV production of ferrous sulphate heptahydrate crystals from pyrite present in coal tailings

The objective of this work was to develop a biohydrometallurgical/UV radiation route to produce ferrous sulphate heptahydrate (melanterite) from the pyrite present in coal tailings. The experimental work was carried out with a pyrite concentrate obtained from gravimetric processing of coal tailing. At laboratory scale it was performed the oxidation of pyrite in an aqueous medium in packed bed leaching columns in an oxidising environment with the presence of acidophilic bacteria (Acidithiobacillus ferrooxidans). The recirculation of the liquor allowed obtaining an iron-rich extract. The conversion of Fe³⁺ to Fe²⁺ was performed using ultraviolet irradiation (UV). Finally, the solution was evaporated allowing the formation of iron sulphate crystals. The results demonstrated that it is possible to produce high purity ferrous sulphate heptahydrate crystals using coal tailings as raw material.     

Multiresidue determination of pesticides in honey samples by gas chromatography–mass spectrometry and application in environmental contamination

A simple and fast multiresidue method has been developed to determine 48 pesticides within the major groups of pesticides (organohalogen, organophosphorous, pyrethroids and organonitrogen) in representative samples of locally produced honey, in Bauru (State of São Paulo, Brazil) during 2003–2004. The recovery results found ranged from 76% to 95% and the limits of detection were lower than 0.01 mg/kg for gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS-SIM). The results indicated that most pesticides found in the samples belonged to the organohalogen and organophosphorous groups and lower levels of residues of some organonitrogen and pyretroids were also detected. Malathion residues were detected in all the samples, in a high concentration, owing to its applications to control dengue mosquitoes in the area studied.     

Influence of the wettability of silicon substrates on the thickness of sol-gel silica films

The fabrication of thick optical films by spinning from solution on silicon substrates is an important technique for integrated optics applications. In particular, several authors have studied the conditions under which the thickness of sol-gel silica films deposited on silicon wafers from solutions of water, tetraethoxysilane (TEOS) and ethanol can be maximized. The influence of processing parameters, such as composition, ageing period of the solution and spinning rate, have been studied. The effect of the wettability of the silicon substrate on the film thickness was investigated. The wetting characteristics of the silicon surface may be changed by adequate chemical cleaning methods. The hydrophilic wafers obtained by controlled oxidation of the silicon were found to have greater affinity to the film forming solution and to lead to thicker films than hydrophobic wafers obtained by etching the silicon surface with HF solution.     

Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil

Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml^-1 or µg F g^-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg^-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible.     

Non‐Linear Predictive Control of a Three‐Phase Catalytic Reactor

In this work, the predictive control of a three‐phase catalytic reactor is considered. A predictive control algorithm, which has a non‐linear internal model represented by functional link networks, is proposed. This network structure has been shown to have a good non‐linear approximation capability, with the advantage that the estimation of its weight is a linear optimization problem. The results show the potential of the proposed procedure when it is applied to the 2‐methyl‐cyclohexanol production process, which is a non‐linear, distributed parameter and time‐varying process, typical of many important industrial systems.     

Method for in-field evaluation of the stator winding connection of three-phase induction motors to maximize efficiency and power factor

The performance of the oversized three-phase induction motors can be improved, both in terms of efficiency and power factor, with the proper change of the stator winding connection, which can be delta or star, as a function of their load. A practical method is proposed to quickly and easily evaluate which stator winding connection is more appropriate for the actual motor load profile, in order to increase the motor efficiency and power factor. This new method is suitable for in-field evaluation, because it requires only the use of inexpensive equipment and has enough accuracy to allow a proper decision to be made. The automatic change of the stator winding connection, as a function of the motor line current, is also analyzed. When properly applied, these methods can lead to the improvement of the efficiency and power factor of permanently oversized motors, motors with a load variation between low load and near full load during their duty cycle, and/or motors driving high-inertia, low duty cycle loads. The proposed methods are particularly suitable to industrial plants where typically many electric motor systems are oversized and/or can have a wide load variation. In these conditions, the active and reactive electrical energy bill can be significantly reduced.     

Principal component analysis applied to feature-oriented band ratios of hyperspectral data: A tool for vegetation studies

This paper presents a simple but effective method to identify and map the distribution of vegetation using hyperspectral data, which involves band ratios and principal component analysis (PCA). Using spectral data from the literature, we devised spectral indices focused on specific vegetation constituents (band positions are in nm): chlorophyll-a (461/422 and 807/638); chlorophyll-b (520/470 and 807/648); @-carotene (520/442); carotenoids (539/490 and 807/490); anthocyanin (510/530); phytochrome P730 (845/730), phytochrome P660 (778/658); lignin (1028/2101); cellulose (2211/2400); nitrogen (1731/1691); and leaf water content (1066/1452). In a second step, these indices were submitted to PCA. PCA eigenvector loadings were examined to decide which of the principal component (PC) images concentrate information directly related to the spectral signatures of specific vegetation constituents. An important aspect of this approach was that it predicted whether the target surface type would be highlighted by dark or bright pixels in the relevant PC image. Finally, the optimal PCs are selected and combined in a colour composite. In this study, we applied this method to atmospherically corrected Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data collected in the Alto Paraíso de Goiás (APG) region of central Brazil. The results from identifying and mapping the distribution of vegetation in the APG region were very encouraging. Photosynthetic and non-photosynthetic vegetation or a mixture of both were mapped on the basis of feature-oriented PC loadings. Discriminations between vegetation types were made, including identifying riparian forests, burn grasslands and resurgence zones, crops and several types of savannah and pastures.     

The use of remote-sensing techniques to monitor dense reservoir networks in the Brazilian semiarid region

Reservoirs are the main water source in the Brazilian semiarid region, especially in the crystalline-geology watersheds, forming high-density reservoir networks (HdRN). However, in most cases, the construction of these reservoirs has been done without technical supervision. The objective of this work was to map and evaluate the spatial distribution of the 25,000 km² Orós Reservoir Basin (ORB) HdRN, in semiarid Brazil, with the help of remote-sensing tools associated with geographic information systems (GIS). Using LANDSAT 5 images of the end of the 2011 rainy season of the ORB, the remote-sensing technique allowed the identification of 6002 polygons, which corresponded to only 4717 reservoirs (implying a misidentification of 21%). Between 2002 and 2011, a 17.5% increase (and 1.81% annual increase) in the number of reservoirs in the basin was observed, still lower than the annual increment from 1970 to 2002, when an average increase of 2.64% per year was observed, in other studies. The perimeter of the reservoirs ranged from 0.250 to 560 km and the individual water surface area ranged from 0.004 to 195.0 km², resulting in a total surface of 465.0 km². Analysing the surface area of the strategic reservoirs, results showed that the estimation of the surface area (from remote sensing with manual polygon adjustment) yielded values very close to those of the on-site monitored areas, with R² = 0.99 and normalized difference index ranging from ?0.02 to +0.09. The reservoir density in the ORB in 2011 was 0.19 reservoirs km^–2, higher than the recommended optimum density of 0.15 reservoirs km^–2 basin. Analysis of reservoir density by municipality recorded values ranging from 0.02 to 0.40 reservoirs km^–2. The sedimentary-geology municipalities presented a reservoir density on average 80% lower than the that of the crystalline-geology municipalities, indicating a strong relationship between geology and reservoir density. Neither population density nor rainfall explained the spatial distribution of reservoirs within the basin, both yielding R² lower than 0.1. This remote-sensing survey of reservoirs demonstrated two major flaws: the misidentification of shadows as reservoirs and the inability to identify the presence of macrophytes, which negatively affected the number and surface area of the target reservoirs. Despite these problems, remote sensing has been shown to be a technique of great potential in the planning and management of water resources in regions with dense reservoir networks.