975 resultados para Mayo, Carlos Alberto


Relevância:

80.00% 80.00%

Publicador:

Resumo:

In this work, electrochemical technology was used to treat synthetic wastewater containing Methyl Red (MR) and Blue Novacron (BN) by anodic oxidation using anodes platinum (Pt) and real samples of textile effluents using DDB anodes and platinum (Pt). The removal of color from the galvanostatic electrolysis of synthetic wastewater MR and BN, and the actual sample has been observed under different conditions (different current densities and temperature variation). The investigation of these parameters was performed in order to establish the best conditions for removal of color and chemical oxygen demand (BOD). According to the results obtained in this study, the electrochemical oxidation processes suitable for the degradation process of color and COD in wastewater containing such textile dyes, because the electrocatalytic properties of Pt and BDD anodes consumption energy during the electrochemical oxidation of synthetic solutions AN and MR and real sample, mainly depend on the operating parameters of operation, for example, the synthetic sample of MR, energy consumption rose from 42,00kWhm-3 in 40 mAcm-2 and 25 C to 17,50 kWhm-3 in 40mAcm-2 and 40 C, from the BN went 17,83 kWhm-3 in 40mAcm and 40°C to 14,04 kWhm- 3 in 40mAcm-2 and 40 C (data estimated by the volume of treated effluent). These results clearly indicate the applicability of electrochemical treatment for removing dyes from synthetic solutions and real industrial effluents

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The present study utilized the thermogravimetry (TG) and optical emission spectroscopy with inductively coupled plasma - ICP / OES to determine the calcium content in tablets of carbonate, citrate and calcium lactate used in the treatment of osteoporosis. The samples were characterized by IR, SEM, TG / DTG, DTA, DSC and XRD. The thermal analysis evaluated the thermal stability and physical-chemical events and showed that the excipients influence the decomposition of active ingredients. The results of thermogravimetry indicated that the decomposition temperature of the active CaCO3 (T = 630.2 °C) is lower compared to that obtained in samples of the tablets (633.4 to 655.2 °C) except for sample AM 2 (Ti = 613.8 oC). In 500.0 °C in the samples of citrate and calcium lactate, as well as their respective active principles had already been formed calcium carbonate. The use of N2 atmosphere resulted in shifting the initial and final temperature related to the decomposition of CaCO3. In the DTA and DSC curves were observed endo and exothermic events for the samples of tablets and active ingredients studied. The infrared spectra identified the main functional groups in all samples of active ingredients, excipients and tablets studied, such as symmetric and asymmetric stretches of the groups OH, CH, C = O. Analysis by X-ray diffraction showed that all samples are crystalline and that the final residue showed peaks indicative of the presence of calcium hydroxide by the reaction of calcium oxide with moisture of the air. Although the samples AM 1, AM 2, AM 3 and AM 6 in their formulations have TiO2 and SiO2 peaks were not observed in X-ray diffractograms of these compounds. The results obtained by TGA to determine the calcium content of the drugs studied were satisfactory when compared with those obtained by ICP-OES. In the AM 1 tablet was obtained the content of 35.37% and 32.62% for TG by ICP-OES, at 6 AM a percentage of 17.77% and 16.82% and for AM 7 results obtained were 8.93% for both techniques, showing that the thermogravimetry can be used to determine the percentage of calcium in tablets. The technique offers speed, economy in the use of samples and procedures eliminating the use of acid reagents in the process of the sample and efficiency results.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Hybrid systems formed from polymers and transition metals have now their physical and chemical properties extensively investigated for use in electronic devices. In this work, Titanium Dioxide (TiO2) from the precursor of titanium tetrabutoxide and the composite system Poly(Ethylene Glycol)-Titanium Dioxide (TiO2-PEG) were synthesized by sol-gel method. The PEG as acquired and TiO2 and composites powders were analyzed by X-Ray Diffraction (XRD), Spectroscopy in the Infrared region with Fourier transform (IRFT), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). In the XRD analysis were observed in the TiO2 crystal faces of one of its polymorphs - anatase phase, crystal planes in Poly (Ethylene Glycol) with considerable intensity and in the composite systems the mixture of crystal faces of their precursors isolated and reduction of crystallinity. The TG / DTG suggested increasing the thermal instability of PEG in the composite powders as TiO2 is incorporated into the system. Spectral analysis presented in the infrared overlapping bands for the polymer and metal oxide, reducing the intensity of symmetric stretching of ligand groups in the main chain polymer and angular deformations; were observed using SEM micrographs of the morphological changes suffered by composite systems with the variation of the oxide concentration. Analyses by impedance spectroscopy indicated that the increased conductivity in composite occurs in line with the addition of the metal oxide concentration in the composite system

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Many pollutants dumped in waterways, such as dyes and pesticides, have become so ubiquitous that they represent a serious threat to human health. The electrochemical oxidation is presented as an alternative clean, efficient and economic degradation of wastewater containing organic compounds and a number of advantages of this technique is to just not make use of chemical reagents, since only electrical energy is consumed during the removal of pollutants organic. However, despite being a promising alternative, still needs some tweaking in order to obtain better efficiency in the elimination of persistent pollutants. Thus, this study sought a relationship between a recently discovered phenomenon that reflects the participation of dissolved oxygen in solution in the electrochemical oxidation process, as an anomaly, present a kinetic model that shows instantaneous current efficiency (ICE) above 100% limited by theory, manifested for some experiments with phenolic compounds with H2SO4 or HClO4 as supporting electrolyte with electrodes under anodic oxidation on boron doped diamond (BDD). Therefore it was necessary to reproduce the data ICE exposes the fault model, and thus the 2-naphthol was used as phenolic compound to be oxidised at concentrations of 9, 12 and 15 mmol L-1, and H2SO4 and HClO4 to 1 mol L-1 as a supporting electrolyte under a current density of 30 mA cm-2 in an electrochemical reactor for continuous flow disk configuration, and equipped with anodes DDB at room temperature (25 oC). Experiments were performed using N2 like as purge gas for eliminate oxygen dissolved in solution so that its influence in the system was studied. After exposure of the anomaly of the ICE model and investigation of its relationship with dissolved O2, the data could be treated, making it possible for confirmation. But not only that, the data obtained from eletranálise and spectroscopic analysis suggest the involvement of other strongly oxidizing species (O3 (ozone) and O radicals and O2 -), since the dissolved O2 can be consumed during the formation of new strong oxidizing species, not considered until now, something that needs to be investigated by more accurate methods that we may know a little more of this system. Currently the performance of the electrocatalytic process is established by a complex interaction between different parameters that can be optimized, so it is necessary to the implementation of theoretical models, which are the conceptual lens with which researchers see

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Corrosion usually occurs in pipelines, so that it is necessary to develop new surface treatments to control it. Surfactants have played an outstanding role in this field due to its capacity of adsorbing on metal surfaces, resulting in interfaces with structures that protect the metal at low surfactant concentrations. The appearance of new surfactants is a contribution to the area, as they increase the possibility of corrosion control at specific conditions that a particular oil field presents. The aim of this work is to synthesize the surfactants sodium 12 hydroxyocadecenoate (SAR), sodium 9,10-epoxy-12 hydroxyocadecanoate (SEAR), and sodium 9,10:12,13-diepoxy-octadecanoate (SEAL) and apply them as corrosion inhibitors, studying their action in environments with different salinities and at different temperatures. The conditions used in this work were chosen in order to reproduce oil field reality. The study of the micellization of these surfactants in the liquid-gas interface was carried out using surface tensiometry. It was observed that cmc increased as salt concentration was increased, and temperature and pH were decreased, while cmc decreased with the addition of two epoxy groups in the molecule. Using the values of cmc and the Gibbs equation, the values of Gibbs free energy of adsorption, area per adsorbed molecule, and surface excess were calculated. The surface excess increases as salt concentration and temperature decreases, increasing as pH is increased. The area per adsorbed molecule and the free energy of adsorption decrease with salt concentration, temperature, and pH increase. SAXS results showed that the addition of epoxy group in surfactant structure results in a decrease in the repulsion between the micelles, favoring the formation of more oblong micellar structures, ensuring a better efficiency of metal coverage. The increase in salt and surfactant concentrations provides an increase in micellar diameter. It was shown that the increase in temperature does not influence micellar structure, indicating thermal stability that is advantageous for use as corrosion inhibitor. The results of inhibition efficiency for the surfactants SEAR and SEAL were considered the best ones. Above cmc, adsorption occurred by the migration of micelles from the bulk of the solution to the metal surface, while at concentrations below cmc film formation must be due to the adsorption of semi-micellar and monomeric structures, certainly due to the presence of the epoxy group, which allows side interactions of the molecule with the metal surface. The metal resistance to corrosion presented values of 90% of efficiency. The application of Langmuir and Frumkin isotherms showed that the later gives a better description of adsorption because the model takes into account side interactions from the adsorbing molecules. Wettability results showed that micelle formation on the solid surface occurs at concentrations in the magnitude of 10-3 M, which isthe value found in the cmc study. This value also justifies the maximum efficiencies obtained for the measurements of corrosion resistance at this concentration. The values of contact angle as a function of time suggest that adsorption increases with time, due to the formation of micellar structures on metal surface

Relevância:

80.00% 80.00%

Publicador:

Resumo:

In this paper, the technique of differential pulse voltammetry (DPV) has been studied for monitoring the concentration of oxalic acid (OA) during their electrochemical oxidation (EO) in acidic medium using platinum anode supported on titanium (Ti / Pt). The DPV was standardized and optimized using a glassy carbon electrode modified with cysteine. The modification with cysteine was developed electrochemically, forming a polymeric film on the surface of the glassy carbon electrode. The formation of the polymer film was confirmed by analysis of scanning electron microscope and atomic force microscope, confirming the modification of the electrode. The electrochemical degradation was developed using different current densities 10, 20 30 and 40 mA cm -2 electrode with Ti / Pt observing the degradation of oxalic acid, and monitored using the method of KMnO4 titration. However, the analyzes with DPV showed the same behavior elimination of oxalic acid titration. Compared with the titration method classical observed and DPV could be a good fit, confidence limits of detection and confirming the applicability of the technique electroanalytical for monitoring the degradation of oxalic acid

Relevância:

80.00% 80.00%

Publicador:

Resumo:

A new self-sustainable film was prepared through the sol-gel modified method, previously employed in our research group; sodium alginate was used as the polymer matrix, along with plasticizer glycerol, doped with titanium dioxide (TiO2) and tungsten trioxide (WO3). By varying WO3 concentration (0,8, 1,6, 2,4 and 3,2 μmol) and keeping TiO2 concentration constant (059 mmol), it was possible to study the contribution of these oxides on the obtained films morphological and electrical properties. Self-sustainable films have analyzed by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XDR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electrochemical Impedance Spectroscopy (EIS). By the IR specters, it was possible identify the TiO2, and posteriorly WO3, addition has provided dislocation of alginate characteristics bands to smaller vibrations frequencies indicating an electrostatic interaction between the oxides and the polymer matrix. Diffractograms show predominance of the amorphous phase in the films. SEM, along with EDX, analysis revealed self-sustainable films showed surface with no cracks and relative dispersion of the oxides throughout the polymer matrix. From Impedance analysis, it was observe increasing WO3 concentration to 2,4 μmol provided a reduction of films resistive properties and consequent improvement of conductive properties

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Materials consisting of perovskite-type oxides (ABO3) have been developed in this work for applications in fuel cell cathodes of solid oxide type (SOFC). These ceramic materials are widely studied for this type of application because they have excellent electrical properties, conductivity and electrocatalytic. The oxides LaMnO3, LaFeO3, LaFe0.2Mn0.8O3 e La0.5Fe0.5MnO3 were synthesized by the method of microwave assisted combustion and after sintering at 800°C in order to obtain the desired phases. The powders were characterized by thermogravimetry (TG), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and voltammetric analysis (cyclic voltammetry and polarization curves). The results obtained by XRF technique showed that the microwave synthesis method was effective in obtaining doping oxides with values near stoichiometric. In general, powders were obtained with particle size less than 0.5 μm, having a porous structure and uniform particle size distribution. The particles showed spherical form, irregular and crowded of varying sizes, according to the analysis of SEM. The behavior of the oxides opposite the thermal stability was monitored by thermogravimetric curves (TG), which showed low weight loss values for all samples, especially those of manganese had its structure. By means of Xray diffraction of the samples sintered at 800°C was possible to observe the formation of powders having high levels of crystallinity. Furthermore, undesirable phases such as La2O3 and MnOx were not identified in the diffractograms. These phases block the transport of oxygen ions in the electrode/electrolyte interface, affecting the electrochemical activity of the system. The voltammetric analysis of the electrocatalysts LF-800, LM-800, LF2M8-800 e L5F5M-800 revealed that these materials are excellent electrical conductors, because it increased the passage of electrical current of the working electrode significantly. Best performance for the oxygen reduction reaction was observed with iron-rich structures, considering that the materials obtained have characteristics suitable for use in fuel cell cathodes of solid oxide type

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The alginates are copolymers of 1→4-linked β-D-mannuronic acid (M) and α-Lguluronic acid (G) residues that are arranjed in a block structure along a linear chain. Titanium dioxide, TiO2, is a ceramic material and can exist in three distinct crystallography forms: anatase, brookite and rutile. composites of organic and inorganic materials have better properties than the components alone. Thus, this study aims to synthesize, characterize and analyze the composite NaAlg-TiO2 in the form of powder and film. The synthesis of composite powders was performed using the sol-gel process and obtain the composite film was performed using the slow evaporation process, then the composites were analyzed by infrared spectroscopy, fluorescence x ray, thermal analysis, attenuated total reflection (ATR), x ray diffraction and impedance spectroscopy. The X ray diffraction patterns of composite powders show that with increasing calcination temperature, there were no complete transition of rutile-anatase crystalline phase, since at all temperatures studied (300, 500, 700, 900 and 1100ºC) were observed peaks of anatase phase. Thermal analysis shows that at 400°C caused the decomposition of sodium alginate in sodium carbonate and above 600°C, we observe an exothermic peak related to the decomposition of sodium carbonate and in the presence of titanium dioxide becomes sodium titanate. The XRD results confirm the formation of sodium carbonate at 700ºC and the formation sodium titanate in the temperature range 900-1100ºC. The sodium titanate influenced the electrical properties of the material, because with increasing temperature there was a decrease in conductivity, probably due to the creation of Ti vacancies, since the sodium can induce the reduction of surface Ti4+ ions into Ti3+ species. The infrared spectra of the composites in the form of powder and film showed a small shift in the bands compared to the spectrum of pure alginate, indicating that these shifts, even small ones, have evidence of miscibility between the polymer and ceramic material

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Three studies were performed using tailings kaolin for the synthesis of zeolite A. The first synthesis of zeolite A was performed using a kaolin waste generated from the beneficiation of kaolin for paper production process was studied. The kaolin waste was thermally activated at a temperature range of 550-800°C. For comparison was performed a synthesis pattern of Zeolite A(procedure IZA). The prepared materials were characterized by 27Al MAS NMR, X-ray diffraction and scanning electron microscopy with microprobe rays. The pre-tramento proved to be the most appropriate and suitable temperatures are between 600 and 700°C. Observed the formation of zeolite A in all materials, reaching 52% crystallinity, and the presence of phase sodalite and amorphous material. The second study was the use of a highly reactive metakaolin originating from the Jari region in the synthesis of zeolite A by a new method of hydrothermal synthesis. The zeolite is obtained pure and highly crystalline employing the Jari kaolin calcined at 600 ° C for 2h when the transformation to metakaolin occurs. Get to zeolite phase A at 4pm. The best crystallization time was of 24 h afforded a crystallinity of 67.9%. The third study was the evaluation of the NaOH / metakaolin and crystallization time on the synthesis of zeolite NaA from a sample of kaolin waste, named Kaolin Coverage. The experiments were performed using statistical design (axial points) and rejoinder the center point. The samples were characterized by X-ray diffraction (XRD), scanning microscopic analysis and chemical analysis using an EPMA microprobe. The results showed that a relationship exists between the amount of NaOH added and the crystallization time. The experiment performed using the lowest ratio NaOH / metakaolin (0.5) and shorter (4 h) produced an amorphous material. The increase ratio of NaOH / metakaolin and crystallization time leads to formation of a more crystalline NaA phase, but the presence of phase with sodalite as impurities

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The contamination by metal ions has been occurring for decades through the introduction of liquid effluent not treated, mainly from industrial activities, rivers and lakes, affecting water quality. For that the effluent can be disposed in water bodies, environmental standards require that they be adequately addressed, so that the concentration of metals does not exceed the limits of standard conditions of release in the receptor. Several methods for wastewater treatment have been reported in the literature, but many of them are high cost and low efficiency. The adsorption process has been used as effective for removal of metal ions. This paper presents studies to evaluate the potential of perlite as an adsorbent for removing metals in model solution. Perlite, in its natural form (NP) and expanded (EP), was characterized by X-ray fluorescence, X-ray diffraction, surface area analysis using nitrogen adsorption (BET method), scanning electron microscopy and Fourier transform infrared spectroscopy. The physical characteristic and chemical composition of the material presented were appropriate for the study of adsorption. Adsorption experiments by the method of finite bath for model solutions of metal ions Cr3+, Cu2+, Mn2+ and Ni2+ were carried out in order to study the effect of pH, mass of the adsorbent and the contact time on removal of ions in solution. The results showed that perlite has good adsorption capacity. The NP has higher adsorption capacity (mg g-1) than the EP. According to the values of the constant of Langmuir qm (mg g-1), the maximum capacity of the monolayer was obtained and in terms of proportion of mass, we found the following order experimental adsorption: Cr3+ (2.194 mg g- 1) > Ni2+ (0.585 mg g-1) > Mn2+ (0.515 mg g-1) > Cu2+ (0.513 mg g-1) and Cr3+ (1.934 mg g-1)> Ni2+ (0.514 mg g-1) > Cu2+ (0.421 mg g-1) > Mn2+ (0.364 mg g-1) on the NP and EP, respectively. The experimental data were best fitted the Langmuir model compared to Freundlich for Cu2+, Mn2+ and Ni2+. However, for the Cr3+, both models fit the experimental data

Relevância:

80.00% 80.00%

Publicador:

Resumo:

In this study, we worked with the validation of a methodology for analysis of bioactive amines in shrimp, considering it to be one of the main products of the northriograndense trade balance, maintaining the state of Rio Grande do Norte topped the list of Brazilian exports of this product the last decade. The sector of the Brazilian shrimp works exclusively with gray shrimp Litopenaeus Vannamei since the late 1990s. This study used liquid chromatography with conductimetric detector, using as the mobile phase methylsulfonic 3 mM acid (MSA) with gradient and phase C18 column with reverse the development of methodology for the analysis of bioactive amines in shrimp. In the sample preparation was used as 5% trichloroacetic acid (TCA) extraction solution. Validation analysis of biotativas amines (putrescine - PUT, histamine - HIST, agmatine - AGM, spermidine - EPD and spermine - EPN) in shrimp, the linear working range was 0.1 to 2.0 mg L-1 to was sensitive, homoscedastic, in effect, selective, accurate and precise array. Thus, considered feasible for these determinations bioactive amines in this array. Determined the concentration of these amines in fresh shrimps (AGM = 0.61 ± 0.05 mg kg- 1 EPD = 2.57 ± 0.14 mg kg-1 and EPN = 1.79 ± 0.11 mg kg-1), and freezing weather predetermined in cooked shrimp (AGM = 6.28 ± 0.18 mg kg-1, EPD = 12.72 ± 0.02 mg kg- 1 and EPN = 22.30 ± 0.60 mg kg-1), the shrimp with twenty-four hour stay at room temperature (PUT = 879.52 ± 28.12 mg kg-1, AGM = 848.13 ± 19.40 mg kg-1, ESPD = 13.59 ± 0.97 mg kg-1 and ESPN = 18.47 + 1.57 mg kg-1). In shrimp subjected to freezing for a week, two weeks, three weeks and four weeks, the results showed that there is an increase in the content of agmatine (7.31 ± 0.21 mg kg-1) while in spermine ( 1.22 ± 0.14 mg kg-1) and spermidine (below limit of quantification) there was a decrease in the freeze time, while there is a decrease in the level of spermidine not reaching detectad. The putrescine was only found in shrimp that remained for 24 hours at room temperature and histamine was not found in any of the samples

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The Layered Double Hydroxides has become extremely promising materials due to its range of applications, easily obtained in the laboratory and reusability after calcination, so the knowledge regarding their properties is of utmost importance. In this study were synthesized layered double hydroxides of two systems, Mg-Al and Zn-Al, and such materials were analyzed with X-ray diffraction and, from these data, we determined the volume density, planar atomic density, size crystallite, lattice parameters, interplanar spacing and interlayer space available. Such materials were also subjected to thermogravimetric analysis reasons for heating 5, 10, 20 and 25 ° C / min to determine kinetic parameters for the formation of metaphases HTD and HTB based on theoretical models Ozawa, Flynn-Wall Starink and Model Free Kinetics. In addition, the layered double hydroxides synthesized in this working ratios were calcined heating 2.5 ° C / min and 20 ° C / min, and tested for adsorption of nitrate anion in aqueous solution batch system at time intervals 5 min, 15 min, 30 min, 1h, 2h and 4h. Such calcined materials were also subjected to exposure to the atmosphere and at intervals of 1 week, 2 weeks and 1 month were analyzed by infrared spectroscopy to study the kinetics of regeneration determining structural called "memory effect"

Relevância:

80.00% 80.00%

Publicador:

Resumo:

In this work a study was done using electrochemical cyclic voltammetry and differential pulse voltammetry for isoniazida (INH), ethambutol (EMB), rifampicina (RIF) and pyrazinamide (PZA) using the electrode boron-doped diamond (BDD) as working electrode. It also verified the applicability of the technique of differential pulse voltammetry in the quantification of the active compounds used in the treatment of tuberculosis, subsequently applying in samples of pharmaceutical formulation. Among the four active compounds studied, isoniazid showed the best results for the detection and quantification using differential pulse voltammetry. At pH 4 and pH 8, for the calibration curves to INH showed good linearity, with quantification limits of 6.15 mmol L-1 (0,844 ppm) and 4.08 mmol L-1 (0.560 ppm) for the respective pH. The proposed method can be used to determine drug isoniazid, for recovery values were obtained in approximately 100%

Relevância:

80.00% 80.00%

Publicador:

Resumo:

This study investigates the chemical species produced water from the reservoir areas of oil production in the field of Monte Alegre (onshore production) with a proposal of developing a model applied to the identification of the water produced in different zones or groups of zones.Starting from the concentrations of anions and cátions from water produced as input parameters in Linear Discriminate Analysis, it was possible to estimate and compare the model predictions respecting the particularities of their methods in order to ascertain which one would be most appropriate. The methods Resubstitution, Holdout Method and Lachenbruch were used for adjustment and general evaluation of the built models. Of the estimated models for Wells producing water for a single production area, the most suitable method was the "Holdout Method and had a hit rate of 90%. Discriminant functions (CV1, CV2 and CV3) estimated in this model were used to modeling new functions for samples ofartificial mixtures of produced water (producedin our laboratory) and samples of mixtures actualproduced water (water collected inwellsproducingmore thanonezone).The experiment with these mixtures was carried out according to a schedule experimental mixtures simplex type-centroid also was simulated in which the presence of water from steam injectionin these tanks fora part of amostras. Using graphs of two and three dimensions was possible to estimate the proportion of water in the production area