The cationic herbicides paraquat, diquat and difenzoquat are largely used in different cultures worldwide. With this, there is an intrinsic risk of environmental contamination when these herbicides achieve natural waters. The goal of this work was to propose a novel and low-cost sorbent for the removal of the cited herbicides from aqueous medium. The proposed sorbent was prepared by loading polyurethane foam with sodium dodecylsulfate. The influence of several parameters (SDS concentration, HCl concentration and shaking time) on the loading process was investigated. The results obtained in this work demonstrated that all studied variables influenced the loading process, having significant effect on the extraction efficiency of the resulted PUF-SDS. At optimized conditions, the PUF was loaded by shaking 200mg of crushed foam with 200mL of a solution containing 5.0×10(-3)molL(-1) SDS and 0.25molL(-1) HCl, for 30min. The obtained PUF-SDS was efficient for removing the three herbicides from aqueous medium, achieving extraction percentages higher than 90%. The sorption process followed a pseudo second-order kinetics, which presented excellent predictive capacity of the amount of herbicide retained with time.

ABSTRACT The goal of this work was to propose a novel method for the solid-phase extraction of the herbicides diquat (DQT2+) and difenzoquat (DFQT+) from aqueous medium using polymeric Amberlite XAD-2 and XAD-4 resins in the presence of sodium dodecylsulfate (SDS). The addition of SDS to the medium was of fundamental importance in order to allow the formation of a negatively charged surface able to sorb the cationic solutes. Several factors that could influence the sorption process, such as SDS concentration in the medium, sorbent mass, pH, ionic strength, and initial concentration of the solutes were investigated. Kinetic studies were also performed to model the system and to identify the mechanisms that operate the sorption process of the herbicides. SDS concentration in the medium presented remarkable influence on the extraction efficiency, achieving maximum values when the ratios [SDS]/[herbicide] were approximately 90, for XAD-2, and 22 and 11 for DQT2+ and DFQT+, respectively, for XAD-4. The sorption process followed a pseudo second-order kinetic in all cases studied. It was also found that an intraparticle diffusion process controlled exclusively the sorption of the herbicides by the Amberlite XAD-2 and XAD-4 resins in the first 15 min, becoming less active with time.

The sulfentrazone dechlorination using bimetallic nanoparticles of Fe/Ni was studied. Different variables that could influence the sulfentrazone conversion were investigated, such as nitrogen atmosphere, pH and dosage of the nanoparticles and initial concentration of sulfentrazone. The best results were obtained using controlled pH (pH 4.0) and 1.0 g L−1 of nanomaterials, resulting in 100 % conversion in only 30 min. Kinetic studies were also conducted, evaluating the influence of different nanoparticle dosages (1.0 to 4.0 g L−1), system temperatures (20 to 35 °C) and nickel levels in the composition of the nanomaterials (0.025 to 0.10 gNi/gFe). The mechanism of sulfentrazone conversion has changed due a direct reduction on the catalytic activity sites and indirect reduction by atomic hydrogen. Both mechanisms have followed pseudo-first order models. The conversion rate improved when the dosage of the nanomaterials, system temperature and nickel content in the composition of the nanocomposites were increased. Finally, the conversion products were elucidated by mass spectrometry and toxicity assays were performed using Daphnia Similis. The results showed that the dechlorination product is less toxic than sulfentrazone.

This work investigates the effect of different variables on acetamiprid degradation in aqueous systems by Fe/Ni nanoparticles. The variables studied were pH (2.0-5.0), temperature (283-313 K), and nanoparticles dosage (0.200 the 0.500 g L-1). The reactions monitoring was made by HPLC. The degradation was greater than 90% in only 5 reaction minutes. The results showed that occurs the formation of hydroxyl radicals in the system because in the presence of tert-butyl alcohol, used as scavenger of these radicals, there was a significant reduction in the degradation rate of approximately 100-10%. Kinetic studies were performed and the results showed that the reaction kinetics followed a pseudo-first order. The degradation rate (k(obs)) was increased when dosage of the nanoparticles and temperature were increased. Regarding pH, the degradation rate increased with decreasing pH of the medium. Finally, the reuse of the nanoparticles was evaluated yielding a 70% of efficiency in acetamiprid degradation. (C) 2016 Elsevier B.V. All rights reserved.

Two major residues are produced by the sugarcane industry, the fibrous fraction following juice extraction (bagasse), and the harvest residue (straw). The structures of the lignins from these residues were studied by pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS), nuclear magnetic resonance (NMR), and derivatization followed by reductive cleavage (DFRC). Whereas the lignin from bagasse has a syringyl-rich p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) molar composition of 2:38:60, the lignin from straw is guaiacyl-rich (H:G:S of 4:68:28). The compositional differences were also reflected in the relative abundances of the different interunit linkages. Bagasse lignin was primarily β–O–4′ alkyl-aryl ether substructures (representing 83% of NMR-measurable linkages), followed by minor amounts of β–5′ (phenylcoumarans, 6%) and other condensed substructures. The lignin from straw has lower levels of β-ethers (75%) but higher relative levels of phenylcoumarans (β–5′, 15%) and dibenzodioxocins (5–5/4–O–β, 3%), consistent with a lignin enriched in G-units. Both lignins are extensively acylated at the γ-hydroxyl of the lignin side-chain (42% and 36% acylation in bagasse and straw), predominantly with p-coumarates (preferentially on S-units) but also with acetates (preferentially on G-units) to a minor extent. Tetrahydrofuran structures diagnostically arising from β–β-coupling (dehydrodimerization) of sinapyl p-coumarate or its cross-coupling with sinapyl alcohol were found in both lignins, indicating that sinapyl p-coumarate acts as a monomer participating in lignification. The flavone tricin was also found in the lignins from sugarcane, as also occurs in other grasses.

The composition of lipophilic phytochemicals in sugarcane bagasse and straw, the two major residues of sugarcane processing, was investigated in detail by gas chromatography and mass spectrometry. The composition of the lipids from sugarcane bagasse and straw was completely different from each other. While the extracts of sugarcane bagasse were dominated by n-aldehydes (ca. 48% of all identified lipids) and n-fatty alcohols (ca. 23%) with lower amounts of n-fatty acids (10%) and steroid ketones (14%), the extracts from sugarcane straw were strongly dominated by n-fatty acids (accounting for ca. 60% of all identified compounds) with significant amounts of steroid compounds, particularly sterols (10%) and steroid ketones (14%). Tocopherols and triterpenols were also found, being particularly abundant among the extractives of sugarcane straw. Sugarcane bagasse and straw can thus be considered as promising feedstocks for obtaining highly valuable phytochemicals of nutraceutical or pharmaceutical interest.

This study has been funded by the Spanish project AGL2011-25379 (co-financed by FEDER funds). Jorge Rencoret thanks the CSIC for a JAE-DOC contract of the program “Junta para la Ampliacion de Estudios” cofinanced by Fondo Social Europeo (FSE). AGL thanks CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior) for financial support.

Abstract The hydraulic behavior of faults during production is a key issue in reservoir management. The correct assessment of dynamic fault hydraulic behavior can optimize the number of wells, the injection design and the well design used in the production network. In an offshore sandstone turbidite reservoir, water breakthrough was detected and attributed to fault reactivation induced by depletion. Assuming that the fault leakage can be attributed to fault reactivation, we describe a geomechanical modeling that was able to support the hypothesis that fault reactivation should be expected in response to depletion in the studied reservoir. The modeling main inputs are the fault and reservoir geometries as well as the complete geomechanical model, built by integrating data from well logs, seismics, pressure measurements, image logs, leakoffs, minifracs, drilling events, measured stress paths and mechanical properties obtained in laboratory or derived by published and in house empirical equations. The program simulates in real time the reactivation of any number of faults in a 3D visualization environment in response to the estimated stress tensor and fault zone mechanical properties for different time steps of the flow model. Any number of scenarios can be simulated in a batch-processing mode, in order to assess the uncertainty associated to the value of several input parameters (e.g. cohesion, friction angle, magnitude and orientation of the maximum horizontal stress, etc.) and to evaluate different production strategies. A key parameter to the successful replication of fault reactivation in the reservoir was the stress path value (A), i.e, the ratio between the variation of the total horizontal minimum stress with respect to the variation of pore pressure during production (A=deltaShmin/deltaP). Leak-off tests performed within the reservoir provide A=0.8, which is a consistent one for an ensemble made by a cemented fault zone in contact with a pristine poorly consolidated sandstone reservoir. Given that such an ensemble is a widespread one, our results might be useful to address dynamic fault hydraulic behavior in poorly consolidated reservoirs in general. Introduction Accessing the hydraulic behavior of faults during production is a key issue in the reservoir management. Faults can produce unexpected compartmentalization and/or faults can be reactivated during injection or depletion, in both cases, dramatically changing the expected distribution of pressures, stresses and water breakthrough in a petroleum field. Conversely, the correct assessment of the dynamic fault hydraulic behavior during production can optimize the number of wells used in the production network, the injection design and the well design as well. Here we present a case of an offshore deep water sandstone turbidite reservoir, where unexpected water breakthrough was detected and attributed to fault reactivation induced by depletion. The reservoir is made by thick channels, with an average porosity of 25% and permeability around 1000 mD. Several faults intersect the oil/water contact within the reservoir. Assuming that the leakage of a fault can be attributed to fault reactivation, in this paper we describe an analytical geomechanical modeling that was able to support the hypothesis that fault reactivation should indeed be expected in response to the observed depletion. First, we will briefly present some key aspects of the methodology. Second, we will describe how the geomechanical model was built and applied to the faults using in-house software solutions. Finally, we will compare and discuss results of fault stability obtained from our analytical geomechanical model under original pressures and depleted pressures.

This study was undertaken to obtain information about the behavior of sulfentrazone in soil by evaluating the sorption and desorption of the herbicide in different Brazilian soils. Batch equilibrium method was used and the samples were analyzed by high performance liquid chromatography. Based on the results obtained from the values of Freundlich constants (Kf), we determined the order of sorption (Haplic Planosol < Red-Yellow Latosol < Red Argisol < Humic Cambisol < Regolitic Neosol) and desorption (Regolitic Neosol < Red Argisol < Humic Cambisol < Haplic Planosol < Red-Yellow Latosol) of sulfentrazone in the soils. The process of pesticide sorption in soils was dependent on the levels of organic matter and clay, while desorption was influenced by the organic matter content and soil pH. Thus, the use of sulfentrazone in soils with low clay content and organic matter (low sorption) increases the probability of contaminating future crops.

We analyzed borehole breakout data and drilling-induced tensile fractures derived from resistivity image logs run at 10 oil wells to derive the orientation of the maximum horizontal stress S-Hmax from the Potiguar Basin in the continental margin of Brazil. Stress magnitudes are derived from density logs for the vertical stress, mini-frac tests for the minimum horizontal stress S-hmin, and rock strength laboratory analysis to estimate the S-Hmax magnitudes. We compared these results with the stress regime and S-Hmax orientation derived from nine earthquake series located in the crystalline basement, where seismicity is concentrated, and previous breakout data from the basin. In the basin, the S-Hmax gradient is 20.0MPa/km, and the S-Hmax/S-hmin ratio is 1.154, indicating a normal tectonic stress regime from 0.5 to 2.0km, whereas the S-Hmax gradient of 24.5MPa/km and S-Hmax/S-hmin ratio of 1.396 indicate a transition from a normal to strike-slip stress regime at 2.5 to 4.0km. The deeper stress regime in the basin is similar to that in the basement at 1-12km depth. This transition of the tectonic stress regime is consistent with an incipient tectonic inversion in the basin. We note that the S-Hmax orientation rotates from NW-SE in the western part of the Potiguar Basin to E-W in its central and eastern parts, roughly following the shoreline geometry, indicating that local features such as flexural stresses influence the local (scale<100km) stress pattern. We also conclude that the basement is critically stressed, but not the basin.

PreviousNext No Access13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013Applications of stress polygon to constrain stress magnitudes and faulting style in Potiguar Basin, northeast BrazilAuthors: Álvaro F. Campassi ReisCláudio C. LimaFrancisco Hilário R. BezerraJoaquim M. FerreiraAderson F. do NascimentoÁlvaro F. Campassi ReisPETROBRAS;Search for more papers by this author, Cláudio C. LimaPETROBRAS;Search for more papers by this author, Francisco Hilário R. BezerraUFRN/PPGGSearch for more papers by this author, Joaquim M. FerreiraUFRN/PPGGSearch for more papers by this author, and Aderson F. do NascimentoUFRN/PPGGSearch for more papers by this authorhttps://doi.org/10.1190/sbgf2013-395 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The construction of the stress polygon is based on the assumption that the admissible stress state on the crust, at any depth or pore pressure, is limited by the frictional strength of preexisting fractures and faults critically oriented to the present tectonic stress field. In this paper we use the stress polygons to constrain stress magnitudes in two different geological domains in Potiguar Basin. In the pos-rift sequence (Açu and Alagamar formations) a present normal faulting regime was observed from 0.5 to 2.0 km, a maximum horizontal stress (SHmax) gradient of 20 MPa/km and a SHmax/Shmin ratio of 1.154. In the deeper rift sequence (Pendência Formation) a transitional (normal to strike-slip) present faulting regime was observed from 2.5 to 4.0km, which is characterized by a SHmax gradient of 24.5 MPa/km and a SHmax/Shmin ratio of 1.396. The deeper regime in the Basin also takes place in the surrounding basement at 1-12 km depth, according to published focal mechanisms. We concluded that this dual stress regime is consistent with an incipient tectonic inversion in the basin. Keywords: tectonics, inversion, sediment, faultsPermalink: https://doi.org/10.1190/sbgf2013-395FiguresReferencesRelatedDetailsCited ByMorphology of submarine canyons along the continental margin of the potiguar basin, NE BrazilMarine and Petroleum Geology 13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013ISSN (online):2159-6832Copyright: 2013 Pages: 2001 publication data© 2013 Published in electronic format with permission by the Brazilian Geophysical SocietyPublisher:Society of Exploration Geophysicists HistoryPublished: 09 Jan 2014 CITATION INFORMATION Álvaro F. Campassi Reis, Cláudio C. Lima, Francisco Hilário R. Bezerra, Joaquim M. Ferreira, and Aderson F. do Nascimento, (2013), "Applications of stress polygon to constrain stress magnitudes and faulting style in Potiguar Basin, northeast Brazil," SEG Global Meeting Abstracts : 1919-1923. https://doi.org/10.1190/sbgf2013-395 Plain-Language Summary KeywordstectonicsinversionsedimentfaultsPDF DownloadLoading ...

Multivariate models were developed using Artificial Neural Network (ANN) and Least Square - Support Vector Machines (LS-SVM) for estimating lignin siringyl/guaiacyl ratio and the contents of cellulose, hemicelluloses and lignin in eucalyptus wood by pyrolysis associated to gaseous chromatography and mass spectrometry (Py-GC/MS). The results obtained by two calibration methods were in agreement with those of reference methods. However a comparison indicated that the LS-SVM model presented better predictive capacity for the cellulose and lignin contents, while the ANN model presented was more adequate for estimating the hemicelluloses content and lignin siringyl/guaiacyl ratio.

The present work reports the development of a method for the determination of lead in aviation gasoline samples by electrothermal atomic absorption spectrometry (ETAAS). The samples were emulsified before injecting into the spectrometer in order to avoid the high instability observed in the signals when the samples were injected directly without any treatment. Stable detergent emulsions were obtained by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of aviation gasoline. These emulsions generated constant integrated absorbance signals for 5h at least. Several parameters related to the emulsion formation (Triton X-100 and HNO3 concentrations) and temperature program (pyrolysis and atomization temperatures and heating rate and the final temperature of the drying step) were evaluated. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion influenced the sensitivity of the lead measurements as well as the heating rate utilized in the drying step. The use of a chemical modifier was necessary, being that the Pd conventional modifier presented better performance than the permanent Ir modifier. The limits of detection and quantification derived for the methodology were 1.2 and 4.0μg L−1. Six samples of aviation gasoline were analyzed and the lead concentrations varied between 11.6 and 64.2μg L−1. A recovery test was performed in order to attest the accuracy of the procedure and recovery percentages between 88 and 112% were observed.

This paper reports the development of a method for the determination of copper and iron in jet fuels employing the electrothermal atomic absorption spectrometry (ETAAS). In order to allow the direct determination of the analytes, the samples were injected into the graphite furnace as detergent emulsions in order to avoid their volatilization during analysis. The results obtained in this work indicated that a stable emulsion can be formed by mixing 1mL of a 7% m/v Triton X-100 solution containing 10% v/v HNO3 with 4mL of jet fuel. The injection of emulsions provided integrated absorbance signals with suitable sensitivity and precision for 300min at least. The addition of chemical modifier was not necessary because background values were always very low, allowing the use of pyrolysis temperature around 1000°C for both analytes. Both Triton X-100 and HNO3 concentrations in the solution used to form the emulsion had remarkable influence on the sensitivity as well as the heating rate employed in the drying step. Under the best conditions established in the present work, limits of detection of 0.50 and 0.46μgL−1 were observed for copper when oil-based and aqueous standards were added to the emulsions for calibration, respectively. For iron, the limits of detection were 0.88 and 0.90μgL−1 for oil-based and aqueous standards, respectively. The method was applied in the determination of Cu and Fe in five samples of jet fuels and a recovery test was performed, producing recovery percentages between 95% and 105%.

The present paper reports the optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry (GF AAS) employing a strategy based on the injection of the samples as detergent emulsions. The method was optimized in relation to the experimental conditions for the emulsion formation and taking into account that the three analytes (Cu, Fe and Pb) should be measured in the same emulsion. The optimization was performed in a multivariate way by employing a three-variable Doehlert design and a multiple response strategy. For this purpose, the individual responses of the three analytes were combined, yielding a global response that was employed as a dependent variable. The three factors related to the optimization process were: the concentration of HNO3, the concentration of the emulsifier agent (Triton X-100 or Triton X-114) in aqueous solution used to emulsify the sample and the volume of solution. At optimum conditions, it was possible to obtain satisfactory results with an emulsion formed by mixing 4 mL of the samples with 1 mL of a 4.7% w/v Triton X-100 solution prepared in 10% v/v HNO3 medium. The resulting emulsion was stable for 250 min, at least, and provided enough sensitivity to determine the three analytes in the five samples tested. A recovery test was performed to evaluate the accuracy of the optimized procedure and recovery rates, in the range of 88–105%; 94–118% and 95–120%, were verified for Cu, Fe and Pb, respectively.

This paper describes the extraction/pre-concentration of Zn from diesel oil and its determination by Flame Atomic Absorption Spectrometry (FAAS), proposed as a novel approach for these kinds of analyses and the multivariate optimization of the proposed procedure. The extraction of Zn is based on the emulsification of an aqueous solution containing Triton X-114 and HNO3 with diesel oil samples followed by breaking of the emulsion by heating. The aqueous phase obtained after the emulsion breaking was collected and used for Zn quantification by FAAS. The methodology was optimized using a Doehlert design and the system variables were the concentrations of surfactant and HNO3 in the solution employed in the emulsification and the temperature used in the emulsion breaking. The ratio between absorbance and the time required to break the emulsions was taken as response. Two sets of experiments, using different emulsifier agents, were run: the first one using Triton X-100 and the second one using Triton X-114. At optimized conditions, the emulsions were prepared by mixing 10mL of diesel oil with 2mL of a solution containing 5% w/v of Triton X-114 and 15% v/v of HNO3 and broken by heating at 80°C. The proposed analytical procedure was applied in the analysis of six real samples of diesel oil and a recovery test was carried out by spiking the samples with known amounts of Zn (25 and 50μgL−1), added as organometallic oiled standard. Recovery percentages achieved in this test were between 92 and 109%.

This present work proposes a new approach for diesel oil preparation for metals determination by ICP-MS. The proposed methodology is based on the extraction of the elements of interest into an aqueous phase employing the extraction induced by emulsion breaking procedure. In this approach, the diesel oil was emulsified with an acid surfactant (Triton X-114) solution in order to form a stable water-in-oil emulsion. Further, the emulsion was broken by centrifugation for 60 min at 3200 rpm, yielding two separated phases: (i) the upper organic phase, containing the diesel oil mixed with the surfactant and (ii) the lower acidic aqueous phase, containing the elements of interest that were extracted from oil. Then, the lower phase was collected, diluted and the analytes were determined by ICP-MS using the internal standardization method. The optimization of the methodology was carried out by analyzing the effect of several parameters that could affect the extraction efficiency such as the concentrations of HNO3 and Triton X-114 in the solution used for emulsification (and extraction), the extraction and collection times and the calibration strategy. The limits of detection and quantification for the elements of interest (Al, Cu, Mn, Ni, Sn and V) were in the range of 26–88 ng L−1 and 86–295 ng L−1, respectively. The accuracy of the methodology was tested by the analysis of spiked samples, since there are no certified samples of diesel oil available in the market. The recovery percentages were in the range of 84–113%. The developed methodology was successfully applied in the metals determination in five commercial diesel oils of different brands.