Estudo das características magnéticas e absorvedoras das ferritas de nizn, niznmn, mnzn, nimg, nicuzn e nicuznmg obtidas via método do citrato precursor

Were synthesized systems Ni0,5Zn0,5Fe2O4, i0,2Zn0,5Mn0,3Fe2O4, Mn0,5Zn0,5Fe2O4, Ni0,5Mg0,5Fe2O4, Ni0,2Cu0,3Zn0,5Fe2O4 and Ni0,2Cu0,3Zn0,5Mg0,08Fe2O4, the precursors citrate method. The decomposition of the precursors was studied by thermogravimetric analysis and spectroscopy in the infrared region, the temperature of 350°C/3h. The evolution of the phases formed after calcinations at 350, 500, 900 and 1100ºC/3h was accompanied by X-ray diffraction using the Rietveld refinement to better identify the structures formed. The materials were also analyzed by scanning electron microscopy, magnetic measurements and analysis of the reflectivity of the material. The samples calcined at different temperatures showed an increase of crystallinity with increasing calcination temperature, verifying that for some compositions at temperatures above 500°C precipitates of second phase such as hematite and CuO. The compositions of manganese present in the structure diffusion processes slower due to the ionic radius of manganese is greater than for other ions substitutes, a fact that delays the stabilization of spinel structure and promotes the precipitation of second phase. The compositions presented with copper precipitation CuO phase at a temperature of 900 and 1100ºC/3h This occurs according to the literature because the concentration of copper in the structure is greater than 0.25 mol%. The magnetic measurements revealed features of a soft ferrimagnetic material, resulting in better magnetic properties for the NiZn ferrite and NiCuZnMg at high temperatures. The reflectivity measurements showed greater absorption of electromagnetic radiation in the microwave band for the samples calcined at 1100ºC/3h, which has higher crystallite size and consequently the formation of multi-domain, increasing the magnetization of the material. The results of absorption agreed with the magnetic measurements, indicating among the ferrites studied, those of NiZn and NiCuZnMg as better absorbing the incident radiation.

Complexos metálicos de cobalto, níquel e cobre com a Pirazina-2-carboxamida e 4- hidrazida ácida piridincarboxílica: síntese e caracterização

This work involved the synthesis, characterization and proposing the molecular structure of coordination compounds involving ligands pyrazine-2-carboxamide (PZA) and 4- hydrazide acidic pyridine carboxylic (INH) and metals of the first transition series (M = Co2+, Ni2+ and Cu2+). For the characterization of the compounds used were analytical techniques such as infrared absorption spectroscopy average (FT-IR) molar conductivity measurements, CHN elemental analysis, EDTA Complexometric, measurement of melting point, X-ray diffraction by powder method, Thermogravimetry (TG) and Differential Thermal Analysis (DTA) and Simultaneous Differential Scanning Calorimetry (DSC). The absorption spectra in the infrared region suggested that the ligand coordination to the metal center occurs through the carbonyl oxygen atom and nitrogen alpha pyrazine ring to those complexes formed with PZA. For INH complexes with metal-ligand coordination is through the carbonyl oxygen and nitrogen of the terminal hydrazide grouping. The conductivity measurements of the complexes in aqueous solution they suggest to all behavior of the type 1:2 electrolytes, and conduct of non-electrolytes in acetonitrile. The results obtained by CHN elemental analysis and EDTA Complexometric allowed to infer the stoichiometry of the compounds synthesized. For all of the complexes obtained was possible to record the melting points, neither of which melted near the melting temperature of the free ligands. The X-ray diffraction showed that the complexes of pyrazinamide exhibited diffraction lines, suggesting that these compounds are crystalline, while compounds of isoniazid, with the exception of cobalt, exhibited diffraction lines, indicating that they are crystalline. The results from the TG-DTA and DSC allowed information regarding the dehydration and thermal decomposition of these complexes

Síntese, caracterizaçao e propriedades catalicas da peneira molecular nanoestruturada modificada com lantanio

The nanostructured molecular sieve SBA-15 was synthesized by the hydrothermal method, and modified with lanthanum with Si/La molar ratios of 25, 50, 75 and 100. The materials were evaluated as catalysts for the cracking of n-hexane model reaction. Type SBA- 15 and LaSBA-15 mesoporous materials were synthesized using tetraetilortosilicato as a source of silica, hydrochloric acid, heptahydrate lanthanum chloride and distilled water. Pluronic P123 triblock. polymer was used as structure template. The syntheses were carried out by 72 hours. The obtained SBA-15 samples were previously analyzed by thermogravimetry, in order to check the conditions of calcination for removal of organic template. Then, the calcined materials were characterized by X-ray diffraction, infrared spectroscopy, adsorption and desorption of nitrogen, scanning electron microscopy and X-ray microanalysis by dispersive energy. The acidity of the samples was determined using adsorption of n-bulinamina and desorption followed by thermogravimetry. It was found that the hydrothermal synthesis method was suitable for the synthesis of the SBA-15 mesoporous materials, with an excellent degree of hexagonal ordering. The reactions of catalytic cracking of n-hexane were carried out using a fixed bed continuous flow microreactor, coupled on-line to a gas chromatograph. From the catalytic evaluation, it was observed that the mesoporous materials containing lanthanum showed different results for the reaction of cracking of nhexane compared to the unmodified mesoporous material SBA-15. As a result of cracking was obtained as main products hydrocarbons in the range of C1 to C5. The catalyst that showed better properties in relation to the acidity and catalytic activity was LaSBA-15 with the ratio Si/La = 50

Avaliação oxidativa do biodiesel de pinhão manso em diferentes processos de purificação

The objective of this study was to analyze the oxidative stability of biodiesel from jatropha obtained from different purification processes, three wet processes with different drying (in a vacuum oven, conventional oven and in anhydrous sodium sulfate) and dry (purification with magnesium silicate adsorbent). Raw materials of different qualities (jatropha crop ancient and recent crop) were used. The Jatropha oil was extracted by mechanical extraction and refined. The Jatropha biodiesel was obtained by the transesterification reaction in ethyl route using alkaline catalysis. The biodiesel samples were characterized by analysis of water content, carbon residue, Absorption Spectroscopy in the Infrared Region and Thermogravimetry. Thermogravimetric curves of purified PUsv* PUsq* and had higher initial decomposition temperatures, indicating that the most stable, followed by samples PU* and PUSC*. Besides the sample SP* is a smaller initial temperature, confirming the sample without purification to be less thermally stable. The percentage mass loss of the purified samples showed conversion of about 98.5%. The results of analyzes carbon residue and infrared suggested that contamination by impurities is the main factor for decreased oxidative stability of biodiesel. The oxidative stability was assessed from periodic monitoring, using the techniques of Rancimat, peroxide index, acid value and Pressurized Differential Scanning Calorimetry. Samples of biodiesel from jatropha which showed better oxidative stability were of the best quality raw material and wet scrubbing: PUsq* with dry chemical, using anhydrous sodium sulfate and PUsv* with vacuum drying, which had oxidative stability 6 hours in Rancimat time 0 days, within the limits established by the Technical Regulation No. 4/2012 of the ANP, without the addition of antioxidant, suggesting that these procedures the least influence on the oxidative stability of biodiesel

Avaliação da poatencialidade da perlita natural e expandida na adsorção de metais

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

Síntese pelo método pechini e caracterização da zircônia dopada com cério e neodímio

In this study five compositions were synthesized zirconia doped with cerium and neodymium ions in the system Ce10-xNdx Zr90O2 with 0,5 ≤ x ≤ 4,0 using the Pechini method. The powders were characterized by thermogravimetric analysis, differential thermal analysis, infrared spectroscopy and X-ray diffraction, with application of Rietveld refinement of the calcination temperatures of 350ºC/3h and 30 minutes at 900ºC/3h. All compositions stabilized with a mixture of cubic and tetragonal phase zirconia. The samples were pressed into bars and sintered at 1500°C/3h and 1500°C/6h, being characterized by Xray diffraction, with application of the Rietveld refinement, density and porosity using Archimedes method, scanning electron microscopy and resistance the three point bending. It has been observed the increase in strength with increasing sintering temperature for the compositions x = 2,0 and x = 4,0. For x = 2,0 the main phase was the cubic with 92,56% with crystallite size of 0,56 μm, density and porosity of 96,82% from 1,36%. For x = 4,0 was a mixture of cubic and tetragonal phase with 21% and 37,98%, respectively. The crystallite size was 54,21 nm and 49,64 nm with a density porosity of 97,45% and 1,32% respectively. In the analysis of the fracture surface was observed a greater amount of grain fracture intragranular type, which contribute to increase the mechanical strength of the ceramic. Increased addition of the neodymium ion in the crystal lattice of the zirconium showed a nearly linear behavior with increasing mechanical strength of the zirconia ceramic. Was obtained a bending resistance of 537 ± 38 MPa for the composition x = 2,0 predominantly attributed to cubic phase with 92,56%

Caracterização e aplicação de vermicultura natural e quimicamente modificada na adsorção de azul de metileno

Chemical modification of clays has been extremely studied in the search for improvements of their properties for use in various areas, such as in combating pollution by industrial effluents and dyes. In this work, the vermiculite was chemically modified in two ways, characterized and evaluated the adsorption of methylene blue dye. First was changed with the addition of a surfactant (hexadecyltrimethylammonium bromide, BHTA) making it an organophilic clay and then by adding an acid (HCl) by acid activation. Some analyzes were performed as X-ray fluorescence (FRX), X-ray diffraction (DRX), adsorption isotherms of methylene blue dye, infrared (FTIR) , scanning electron microscopy (SEM), thermal gravimetric analysis and spectroscopy energy dispersive (EDS). Analysis by FRX of natural vermiculite indicates that addition of silicon and aluminum, clay presents in its structure the magnesium, calcium and potassium with 16 % organic matter cations. The DRX analyzes indicated that the organic vermiculite was an insertion of the surfactant in the space between the lamellae, vermiculite and acid partial destruction of the structure with loss of crystallinity. The adsorption isotherms of methylene blue showed that there was a significant improvement in the removal of dye to the vermiculite with the addition of cationic surfactant hexadecyltrimethylammonium bromide and treatment with acid using HCl 2 mol/L. In acid vermiculites subsequently treated with surfactant, the adsorption capacity increased with respect to natural vermiculite, however was much lower compared vermiculite modified with acid and surfactant separately. Only the acidic vermiculite treated with surfactant adjusted to the Langmuir model. As in the infrared spectrometry proved the characteristics of natural vermiculite. In the organic vermiculite was observed the appearance of characteristic bands of CH3, CH2, and (CH3)4N. Already on acid vermiculite, it was realized a partial destruction with decreasing intensity of the characteristic band of vermiculite that is between 1074 and 952 cm-1. In the SEM analysis, it was observed that there was partial destruction to the acid treatment and a cluster is noted between the blades caused by the presence of the surfactant. The TG shows that the higher mass loss occurs at the beginning of the heating caused by the elimination of water absorbed on the surface between layers. In the organic vermiculite also observed a loss of mass between 150 and 300 °C caused decomposition of the alkylammonium molecules (surfactants)

Síntese e caracterização de óxidos de zinco e de magnésio suportados em A1SBA-15 para produção de biodiesel

To overcome the challenge of meeting growing energy demand in a sustainable way, biodiesel has shown very promising as alternative energy can replace fossil fuels, even partially. Industrially, the biodiesel is produced by homogeneous transesterification reaction of vegetable oils in the presence of basic species used as catalysts. However, this process is the need for purification of the esters obtained and the removal of glycerin formed after the reaction. This context, the alternative catalysts have that can improve the process of biodiesel production, aiming to reduce costs and facilitate its production. In this study, the AlSBA-15 support with Si / Al ratio = 50 was synthesized, as like as the heterogeneous catalysts of zinc oxide and magnesium supported on mesoporous AlSBA-15 silica, in the concentrations of 5, 10, 15 and 30 %, relative to the support. The textural properties and structural characterization of catalysts and supports were determined by techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) coupled to the chemical analyzer, adsorption / desorption of N2, thermal analysis (TG / DTG), absorption spectroscopy in the infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Characterization results indicated that the support AlSBA-15 retained the hexagonal ordered after the incorporation of zinc oxide and magnesium oxide in the holder. For heterogeneous catalysts, ZnO-AlSBA-15, that was observed the presence of zinc oxide nanoparticles dispersed in the surface and interior channels of the mesoporous and microporous support. The catalytic activity was evaluated by the transesterification reaction of sunflower oil via methylic route, and some reaction parameters were optimized with the most active catalyst in biodiesel production by sunflower oil. For the series of heterogeneous catalysts, the sample with 30 % ZnO supported on AlSBA-15 showed a better conversion of triglyceride to methyl esters, about 95.41 % of reaction conditions: temperature 175 °C, with molar ratio of 42:1, stirring at 200 rpm and under a pressure of 14 bar for 6 h. The catalyst MgO-AlSBA-15 showed no catalytic activity in the studied reactions

Síntese hidrotérmica e caracterização estrutural de titanatos nanotubulares para aplicação na captura do dióxido de carbono

Nanostructured materials have been spreading successfully over past years due its size and unusual properties, resulting in an exponential growth of research activities devoted to nanoscience and nanotechnology, which has stimulated the search for different methods to control main properties of nanomaterials and make them suitable for applications with high added value. In the late 90 s an alternative and low cost method was proposed from alkaline hydrothermal synthesis of nanotubes. Based on this context, the objective of this work was to prepare different materials based on TiO2 anatase using hydrothermal synthesis method proposed by Kasuga and submit them to an acid wash treatment, in order to check the structural behavior of final samples. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), adsorption/desorption of N2, thermal analysis (TG/DTA) and various spectroscopic methods such as absorption spectroscopy in the infrared (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All the information of characterizations confirmed the complete conversion of anatase TiO2 in nanotubes titanates (TTNT). Observing the influence of acid washing treatment in titanates structure, it was concluded that the nanotubes are formed during heat treatment, the sample which was not subjected to this process also achieved a complete phase transformation, as showed in crystallography and morphology results, however the surface area of them practically doubled after the acid washing. By spectroscopy was performed a discussion about chemical composition of these titanates, obtaining relevant results. Finally, it was observed that the products obtained in this work are potential materials for various applications in adsorption, catalysis and photocatalysis, showing great promise in CO2 capture

Síntese e caracterização de compostos de coordenação homolépticos e heterolépticos com o ligante ácido kójico

The present work has as main objective to contribute to the coordination chemistry of the ligand kojic acid, with the synthesis and characterization of the homoleptic compounds [Al(kj)3], [Fe(kj)3], [Fe(kj)2], [Cu(kj)2] e [Ru(kj)3], and the new heteroleptic complexes, trans- K2[Fe(kj)2(CN)2] and trans-Na2[Ru(kj)2(CN)2]. The obtained compounds were characterized by vibrational spectroscopy in the infrared region (IV) and Electronic spectroscopy in the ultraviolet and visible region (Uv-Vis). The infrared results indicated the coordination of the bidentate ligand kojic acid, due to reductions in the values of the stretching frequencies of the carbonyl and double bonds, compared to the free ligand for all complexes obtained. The presence of new vibrational modes indicated the change of symmetry of the molecules in the new compounds synthesized. Additionally, the presence of vibrational modes assigned to metal-oxygen also contributed to confirm the ligand coordinating to the metal ions. Through this technique, was also possible to perform correlations of the numbers of vibrational modes, in the region 1400-900 cm-1 and the compounds geometry. The heteroleptic compounds exhibited υC≡N in 2065 and 2053 cm-1, respectively, for the trans-K2[Fe(kj)2(CN)2] and trans-Na2[Ru(kj)2(CN)2], indicating coordination of the cyano ligand to metal ions FeII e RuII. Comparing the obtained values with literature data was possible to identify the complex isomerism as trans. In relation to the results of electronic spectroscopy, studies of pH variation of kojic acid provided information on the distribution of electron density in the molecule, showing characteristic spectral profile of kojic ion and its protonated form (Hkj, kojic acid), with two bands at 215 and 269 nm, or deprotonated (kj-), with bands at 226 and 315 nm. The electronic spectra obtained for all complexes in aqueous medium, in the ultraviolet region, exhibited variations of the energies assigned to kojic acid intraligand transitions while in the visible region, only transitions assigned to charge transfer of iron and ruthenium complex have been identified

Síntese e caracterização de ferritas de níquel dopadas com cobalto e efeito da substituição nas suas propriedades magnéticas

The ferrite composition Ni1 - xCoxFe2O4 (0 ≤ x ≤ 0.75) were obtained by the method of microwave assisted synthesis and had their structural and magnetic properties evaluated due to the effect of the substitution of Ni by Co. The compounds were prepared: according to the concept of chemical propellants and heated in the microwave oven with power 7000kw. The synthesized material was characterized by absorption spectroscopy in the infrared (FTIR), Xray diffraction (XRD) using the Rietveld refinement, specific surface area (BET) , scanning electron microscopy (SEM) with aid of energy dispersive analysis (EDS) and magnetic measurements (MAV). The results obtained from these techniques confirmed the feasibility of the method of synthesis employed to obtain the desired spinel structure, the ferrite, nickel ferrite as for nickel doped with cobalt. The results from XRD refinement ally showed the formation of secondary phases concerning stages α - Fe2O3, FeO, (FeCo)O e Ni0. On the other hand, there is an increase in crystallite size with the increase of cobalt in systems, resulting in an increased crystallinity. The results showed that the BET systems showed a reduction in specific surface area with the increase of cobalt and from the SEM, the formation of irregular porous blocks and that the concentration of cobalt decreased the agglomerative state of the system. The magnetic ferrites studied showed different characteristics according to the amount of dopant used, ranging from a very soft magnetic material (easy magnetization and demagnetization ) - for the system without cobalt - a magnetic material with a little stiffer behavior - for systems containing cobalt. The values of the coercive field increased with the increasing growth of cobalt, and the values of saturation magnetization and remanence increased up to x = 0,25 and then reduced. The different magnetic characteristics presented by the systems according to the amount of dopant used, allows the use of these materials as intermediates magnetic

Aplicação da termogravimetria na determinação do teor de ferro em comprimidos: um estudo comparativo com a espectrofotometria

This study used the Thermogravimetry (TG) and molecular absorption spectroscopy in UV-visible region to determine the iron content in herbal medicinal ferrous sulfate used in the treatment of iron deficiency anemia. The samples were characterized by IR, UV, TG / DTG, DTA, DSC and XRD. The thermoanalytical techniques evaluated the thermal stability and physicochemical events and showed that the excipients interfere in the decomposition of the active ingredients. The results of thermogravimetry showed that the decomposition temperature of the active principle Fe2(SO4)3 (T = 602 °C) is higher as compared to samples of tablets (566 586 °C). In the DTA and DSC curves were observed exothermic and endo events for samples of medicines and active analysis. The infrared spectra identified key functional groups exist in all samples of active ingredients, excipients and compressed studied, such as symmetric and asymmetric stretching of OH, CH, S=O. The analysis by X-ray diffraction showed that all samples had crystallinity and the final residue showed peaks indicating the presence of silicon dioxide, titanium dioxide and talc that are excipients contained in pharmaceutical formulations in addition to iron oxide. The results obtained by TG to determine the iron content of the studied drugs showed a variance when compared with those obtained by theoretical and UV-visible, probably due to formation of a mixture of Fe2O3 and Fe2(SO4)3. In one tablet was obtained FE content of 15.7 % and 20.6 % for TG by UV-visible, the sample EF 2 was obtained as a percentage of 15.4 % and 21.0 % for TG by UV-visible . In the third SF samples were obtained a content of 16.1 % and 25.5 % in TG by UV-visible, and SF 4 in the percentage of TG was 16.7 % and 14.3 % UV-visible

Adsorção dos gases NH3, NO e H2S em fosfato de vanadila, hidrogeno fosfato de vanadila e fosfatos de vanadila dopados por Al, Co, Mn e Cr

In this work were synthesized the materials called vanadyl phosphate, hydrogen vanadyl phosphate and vanadyl phosphate doped by transition metals with the aim in adsorption the following compounds: ammonia, hydrogen sulfide and nitrogen oxide. To characterize the starting compounds was used DRX, FTIR, FRX and TG analysis. After the characterization of substrates, proceeded de adsorption of NH3 and H2S gases in reactor, passing the gases with continuous flow for 30 min and room temperature. Gravimetric data indicate that the matrices of higher performance in adsorption of ammonia was those doped by aluminum and manganese, obtaining results of 216,77 mgNH3/g and 200,40 mgNH3/g of matrix, respectively. The matrice of higher performance in adsorption of hydrogen sulfide was that doped by manganese, obtaining results of 86,94 mgH2S/g of matrix. The synthesis of substrates VOPO4.2H2O and MnVOPO4.2H2O with nitrogen oxide was made in solution, aiming the final products VOPO4.G.nH2O and MnVOPO4.G.nH2O (G = NO and n = number of water molecules). The thermo analytical behavior and the infrared spectroscopy are indicative of formation of VOPO4.2,5NO.3H2O compound. Results of scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) of materials vanadyl phosphate and vanadyl phosphate modified after reaction in solid state or in solution with the gases show morphology changes in substrates, beyond the formation of orthorhombic sulfur crystals over their respective hosts when these adsorb hydrogen sulfide

Estudo do desempenho de resinas poliméricas para remoção de H2S do gás natural

The natural gas (NG) is a clean energy source and found in the underground of porous rocks, associated or not to oil. Its basic composition includes methane, ethane, propane and other components, like carbon dioxide, nitrogen, hydrogen sulphide and water. H2S is one of the natural pollutants of the natural gas. It is considered critical concerning corrosion. Its presence depends on origin, as well as of the process used in the gas treatment. It can cause problems in the tubing materials and final applications of the NG. The Agência Nacional do Petróleo sets out that the maximum concentration of H2S in the natural gas, originally national or imported, commercialized in Brazil must contain 10 -15 mg/cm3. In the Processing Units of Natural Gas, there are used different methods in the removal of H2S, for instance, adsorption towers filled with activated coal, zeolites and sulfatreat (solid, dry, granular and based on iron oxide). In this work, ion exchange resins were used as adsorbing materials. The resins were characterized by thermo gravimetric analysis, infrared spectroscopy and sweeping electronic microscopy. The adsorption tests were performed in a system linked to a gas-powered chromatograph. The present H2S in the exit of this system was monitored by a photometrical detector of pulsing flame. The electronic microscopy analyzes showed that the topography and morphology of the resins favor the adsorption process. Some characteristics were found such as, macro behavior, particles of variable sizes, spherical geometries, without the visualization of any pores in the surface. The infrared specters presented the main frequencies of vibration associated to the functional group of the amines and polymeric matrixes. When the resins are compared with sulfatreat, under the same experimental conditions, they showed a similar performance in retention times and adsorption capacities, making them competitive ones for the desulphurization process of the natural gas

Preparo e caracterização de membranas de quitosana modificadas com poli (ácido acrílico)

The aim of this study was to generate an asymmetric biocompactible and biodegradable chitosan membrane modified by the contact with a poly(acrylic acid) solution at one of its sides at room temperature and 60◦C. The pure chitosan membrane, as well as the ones treated with poly(acrylic acid) were characterized by infrared spectroscopy (FTIRATR) at angles of 39◦, 45◦ and 60◦ , swelling capacity in water, thermal analysis (TG/DTG), scanning electronic microscopy (SEM) and permeation experiments using metronidazole at 0,1% and 0,2% as a model drug. The results confirmed the presence of ionic interaction between chitosan and poly(acrylic acid) by means of a polyelectrolyte complex (PEC) formation. They also showed that such interactions were more effective at 60◦C since this temperature is above the chitosan glass transition temperature wich makes the diffusion of poly(acrylic acid) easier, and that the two treated membranes were asymmetrics, more thermically stable and less permeable in relation to metronidazole than the pure chitosan membrane