Repositório RCAAP

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The Brazilian enormous potential in the availability of various raw materials in the production of biodiesel requires close attention, because the production of vegetable oils in Brazil is based, mostly, on soybean. However, the increased demand for soybean oil provided the elevation of its market price and, consequently, the cost of biodiesel, making it more expensive than diesel. Seeking a greater diversity of oil in biodiesel production and avoiding competition with food products, the jatropha curcas is becoming a very viable alternative to planting on degraded land, semi-arid or for reforestation. The superior productivity of Jatropha in soybean and its resistance to adverse conditions favor its growth. The use of jatropha s oil is an alternative to soybean and can be used without the need of performing all stages of the oil s treatment, requiring only minor adaptations or the choice of different methods of catalysis. The objective of this work was to study different types of catalysts (alkaline, acid and double), in two different types of vegetable oil from jatropha curcas: Crude and refined oils, in order to observe the physico-chemical properties of the produced biodiesel, as well as their oxidation properties.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The chemical fertilizer used in crops to meet the nutritional deficiencies of soil and consequently increase its fertility and productivity, can be a major responsible for contaminating the soil with heavy metals. In this way, this work presents an optimization study to extract copper, lead and cadmium in samples of mineral fertilizer (inorganic) using an ultrasonic bath for the sample preparation and determination by a flame atomic absorption spectrometry, comparing the results obtained by the proposed method with the official method designated by the Brazilian Ministry of Agriculture (Ministério da Agricultura, Pecuária e Abastecimento - MAPA). For the development of this work, different parameters were evaluated, such as the sonication time, the sample mass, composition and concentration of the extracting solution, in order to obtain the best condition for extraction and analytical determination of metals. After defining some parameters, comparison tests were performed using extraction by vortex agitation with ultrasonic bath in order to assess possible changes in extraction efficiency. A central composite design (PCC) comprising a two-level factorial design with three variables (23), plus a central point in triplicate and even experiments in six axial points (± α1), totaling 17 experiments was then performed to optimize the method employing a sample certified by the National Agency of Promotion of Fertilizers (Agência Nacional de Difusão de Adubos, ANDA). Other five samples, two of them certified by ANDA, were also analyzed using the optimized conditions. The favorable analytical conditions were 70 mg of sample, 5 min sonication and 50% (v/v) HNO3 as extractor solution, which provided efficiency extraction higher than 80% in most cases. The proposed method of sample preparation offers as main advantages the fastness, versatility and reduction of the volume of acids and sample, and then diminishes waste generation.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Aqueous solutions containing the commercial azo dye Red GRLX-220 were ozonated in acid (pH 4) and alkaline (pH 12) conditions. Ozone was electrochemically generated using a laboratory-made electrochemical reactor and applied using semi-batch conditions and a column bubble reactor. The applied current density was 20.0 and 25.0 A in acidic and basic media, respectively, resulting in a current efficiency of 8.9% and 6.4%, corresponding to an ozone application rate of 0, 550 g h and 0.480, respectively. Under these conditions and after 65 minutes of ozonation resulted in a large discoloration of the effluent (99% in acidic and 97% in alkaline media). The kinetics of color removal presented a dependence on the ozonation time through the presence of two linear segments, which were interpreted using a kinetic model of pseudofirst- order. Accordingly, it proposes the formation of intermediate species that precede the final stage of degradation. Both the removal of chemical oxygen demand (COD) and totality organic carbon (TOC) were slightly higher in alkaline media which were attributed to the presence of hydroxyl radical in the oxidation step. Evaluation of the oxidation feasibility by means of the COD/TOC radio indicates that the ozonation processes in both acid and alkaline conditions leads to a reduction in recalcitrance of the soluble organic matter. The calculations performed for the residual ozone showed that the use of the gas is maximum for short reaction time. The toxicity studies showed that the ozonation byproducts present lower toxicity than the initial solution of the dye.

This work reports the development of a quick and easy method for simultaneous determination of paracetamol (PA) and caffeine (CA) in pharmaceutical formulations using Flow Injection Analysis with Multiple Pulse Amperometric detection (FIA-MPA). A singleline flow injection system was employed using a home-made electrochemical wall-jet cell in the three electrode configuration. Boron-doped diamond electrode (BDD; ~8000 ppm) was used as the working electrode. The strategy used in the simultaneous determination of PA and CA by FIA-MPA was the application of three sequential and cyclic potential pulses in function of the time: (1) +1.20 V/50ms: oxidation of PA and selective quantification of PA; (2) +1.55 V/50ms: oxidation of both analytes (CA e PA) and quantification of CA through the subtraction of the current signal detected at + 1.20 V. However the current detected at +1.20 V should be multiplied for a correction factor; (3) +0.40V/100ms: potential pulse applied in order to avoid contamination of BDD working electrode (probably due to the adsorption of PA or CA or oxidations products). The PA oxidation current detected at +1.20 V is greater than the PA current detected at +1.55 V, a simple subtraction between currents detected at the two potential pulses does not directly yield the CA oxidation current. To circumvent this problem, we applied a correction factor (fator = iPA+1,55 V/iPA+1,2 V) that corresponds to the exact difference between the current detected for PA at +1.20 V and +1.55 V. Then, the current originating from CA oxidation detected at +1.55 V can be calculated using the following equation: [iCA = i+1,55 V (fator x i+1,20 V)]. Besides this, several parameters of the FIA-MPA system were studied and/or optimized: potential pulses times, current sampling in each transient signal, flow rate and injection volume. Both compounds displayed good linearity over a large concentration range (1.0 755 mg L-1 for PA and 1.0 315 mg L-1 for CA), with excellent correlation coefficients for both analytes (R = 0.999). The correction factor is constant over a large PA concentration range (9.9-177.0 mg L-1; correction factor = 0.771 ± 0.012; n = 13). The proposed method was used for the determination of PA and CA in pharmaceutical formulations and the obtained results were similar to those obtained by HPLC. Recovery studies were also carried out (~ 100 %).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

In this work was developed an electrochemical immunosensor that can detect label free specific antibody for visceral leishmaniasis using graphite electrode modified with poly(4-HPA) as a platform and DPV as electrochemical technique support. Therefore, investigations of main structural characteristics, thermal and electrochemical poly(4-HPA), obtained by electropolymerization of acid 4-HPA, were conducted using the following techniques: FTIR, UV-vis and Fluorescence. The FTIR spectra showed that the functional groups present in the monomer are preserved and that new groups are formed after electropolymerization, and the obtained polymer is 1,2,4,5-tetra-substituted, with strong evidences that these two new substituents are diphenyl ethers and ring-ring bonds, which justifies the increase in the extension of conjugation and the presence of new chromophore groups observed in UV-vis and Fluorescence studies. Thus, it was possible to discuss about the structure of poly(4-HPA), as well as propose the possible reaction mechanisms involved in its formation. These studies were of great importance in the search for a better understanding and discussion of the results. The thermal stability of the polymer, evaluated by TGA shows that the poly(4-HPA) presents a complex and heterogeneous structure and do not exhibits good thermal stability after 100 ° C. It was also investigated the growth of polymer in function of the number of potential scans. Through of this investigation it was possible obtained a profile for the increased electrochemical response of this material in relation to the time of electropolymerization, and such profile showed that the number of potential scans used in electrosynthesis is a good parameter to be used at the studies of this material. For the immunosensor development, the immobilization of the rK39 antigen, specific for visceral leishmaniasis, onto EG/poly(4-HPA) was confirmed through electrochemical studies. A electrochemical detection of IgG+ was conducted using CV and DPV techniques, using Coomassie Brilliant Blue G-250 and ruthenium hexamine II chloride as possible indicators of the formation of Antigen-Antibody complex. The Coomassie was efficient to indicate the surface modification of EG/poly(4-HPA) with rK39, however, did not show satisfactory sensitivity for IgG+, as well as selectivity for the non-complementary target (IgG-, negative control). However, the ruthenium hexamine II chloride, showed high efficiency to indicate the surface modification of EG/poly (4-HFA) with rK39 and good sensitivity for IgG+ and selectivity towards IgG-; enabling the development of the electrochemical immunosensor proposed in this work.

Dramatic increases in the price of crude oil, and consequently, transportation fuels, coupled with increased environmental concerns have resulted in rapid growth in biodiesel production. Thus, so does production of the primary coproduct, glycerol, which has become a worrying factor because for every ton of biodiesel produced, are generated 100 Kg of glycerol. Because this reality research has been developed to search alternatives for the use of glycerol. So, an application for this alcohol is the search for value-added chemicals such as propylene glycol and others. Reactions of aqueous phase reforming of glycerol were performed without the addition of hydrogen and streaming using monometallic catalysts of Re and Pt and bimetallic Pt-Re all supported on carbon Black . We used an aqueous solution of glycerol feeding 80% m / m, temperature of 275°C and 30 bar pressure. WHSV was varied and the content thus evaluating Re, its influence on the Pt catalysts, the stability and activity. The catalysts was characterized for temperature-programmed reduction (TPR); chemisorption of CO studies; temperature-programmed desorption-CO (TPD-CO); temperature-programmed desorption-isopropylamine (TPD-IPA). Studies of RTP for the bimetallic catalysts Pt-Re showed that rhenium interacts strongly with the platinum and possibly, precursor species are formed bimetallic alloy. CO chemisorption experiments resulted in the formation of the alloys of Pt-Re / C. The results of TPD-CO demonstrated that the addition of Re to the catalyst Pt / C changes the surface of Pt and collaborates with the weakening of bond strength of the CO molecule to the sites involved. Through the catalytic reactions studied and a qualitative analysis of chromatograms from high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GCMS) was possible to verify from the reaction of aqueous phase reforming of glycerol, the formation 1,2-propanediol and other products.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

In the present work was carried out experimental design for the best reaction conditions of the process of transesterification by soybean oil. There were two plans for an ethanol process route and two for the route methyl, the variables employed were: time (min), speed (RPM), alcohol: oil molar ratio, percentage of catalyst, catalyst type, temperature (0C). The catalysts tested were: NaOH, KOH and potassium ethoxide to the ethylic route and for the methylic route were: NaOH, KOH and potassium methoxide. The condition in which was obtained the highest yield for the production of biodiesel via ethylic route was: time: 60 minutes, speed 100 rpm; ethanol: oil molar ratio: 12:1; percentage of catalyst: 0.2%; type catalyst: potassium ethoxide, temperature: 350C. The condition in which was obtained the highest yield for biodiesel production via methanol route was: time: 30 minutes, speed: 100 rpm, methanol: oil molar ratio: 6:1; percentage of catalyst: 0.2%; type catalyst: KOH; temperature: 55 0C. The biodieseis obtained under optimum conditions of each plan were submitted to physical-chemical properties: acid value, moisture content, density at 20 0C, kinematic viscosity at 40 0C, oxidative stability and carbon residue. The results are consistent with the allowable values of ANP (Resolution 07/2008), with the exception of the parameter oxidative stability of methyl biodiesel from soybeans. The soybean oil used as feedstock for biodiesel production was also subjected to physical and chemical analysis and the values showed that the transesterification of oil would be viable.

A simple, effective and low cost for copper determination in biodiesel, without decomposition of the sample is presented. The samples of biodiesel were diluted in a hydro-ethanolic solution (containing HCl as supporting electrolyte) generating a homogeneous ternary system (water-ethanol-biodiesel) in which copper was detected directly using potentiometric stripping constant current using a gold working electrode. The composition of the ternary system was optimized homogeneous aqueous solution of 5 mL 0.1 mol L-1 HCl, 15 mL of ethanol and 0.1 mL (0.088 g) of biodiesel. The detection limit was estimated at 200 ng g-1 (applying deposition time 300 s). In validation tests the method was free from interference, matrix and other metals, and their accuracy was compared with square wave voltammetry with anodic stripping (SWASV) in aqueous solution after extraction of the metal and atomic absorption spectrometry flame (FAAS) after acid mineralization. In another study, the proposed method was applied for copper determination in biodiesel samples exposed to simulated conditions of storage. The samples of biodiesel produced in the laboratory were doped with the antioxidant tert-butyl hydroquinone (TBHQ). The storage conditions were simulated by static immersion corrosion tests in biodiesel (with and without TBHQ) using copper plates. Measures of oxidative stability (induction period by Rancimat) and release the metal in different stages of corrosion were carried out. After 24 h of static immersion test, pure biodiesel and doped with TBHQ had induction times below the limit set by EN 14214 (6 h). The release of copper was more intense in the pure biodiesel (without TBHQ) showing that the corrosion process is delayed in the presence of TBHQ, which acted as a corrosion inhibitor. In parallel, mass spectrometry revealed the presence of considerable amounts of tert-butyl quinone (TBQ) in biodiesel doped with TBHQ and exposed to the etching process. Thus, we do believe that TBHQ molecules adsorb on the copper surface to inhibit corrosion, and then they are catalytically oxidized to TBQ. The results of mass spectrometry also indicated the formation of new molecules of high molecular weight only in the biodiesel doped with TBHQ and deteriorated by the corrosion process. MS-MS spectra provided evidence of the formation of new molecules originated from free radicals of long chain molecules (derived from fatty acids) and TBQ radicals during biodiesel deterioration.

This work describes the development of analytical methodology for Ni(II) determination in ethanol fuel applying also to other alcoholic matrices (whisky and sugar cane spirits). The method involves the use of a flow injection (FI) preconcentration system and flame atomic absorption spectrometry (FAAS). The flow manifold was made up of four threeway solenoid valves, peristaltic pump and a minicolumn packed with the biosorbent obtained from tangerine peel Ponkan trated with NaOH. Middle Infrared Spectroscopy, Thermogravimetric Analysis and X-ray Diffraction were used to characterize the biosorbent. The point of zero charge of in natura tangerine peel and trated with NaOH were 4.8 and 6.0, respectively. Adsorption isotherms were used in order to identify the largest capacity of removal and the mechanisms involved between the material and the Ni(II). Multivariate methods were used (full factorial design 24 and response surface) for examine the best chemical and flow variables. The optimized conditions of the preconcentration system were: sample flow rate 4.27 mL min-1, eluent concentration of 1.0 mol L-1, biosorbent mass to 48.22 mg and sample initial pH 6.0. Test of homogeneity and stability (40 preconcentration/elution cycles) of the biosorbent used in the proposed method, as well evaluating the linear range (10.3 - 75 μg L-1), precision (R.S.D. de 0.90%), enrichment factor (11.783), sampling frequency (15 samples h-1), efficiency of concentration (3.1008 min-1), consumption index (0.85 ml), detection limits (3.1 μg L-1) and quantification (10.3 μg L-1) were performed to assess the analytical performance. The proposed methodology was applied in alcohol fuel samples, sugar cane spirits and whisky were found recovery to 99 - 110%.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Campomanesia pubescens (DC.) O. Berg, também conhecida como gabiroba pilosa, pertence à família Myrtaceae. Este gênero apresenta 25 espécies distribuídas do México à Argentina, e 15 delas são nativas do Brasil, e podem ser encontradas nos estados da Bahia, Espírito Santo, Minas Gerais, São Paulo, Goiás, Distrito Fede-ral, Mato Grosso do Sul e no Tocantins. O objetivo deste trabalho foi avaliar o teor de compostos fenólicos, identificar os constituintes voláteis (óleo essencial), determinar a atividade antioxidante e antimicrobiana de partes da planta (raiz, caule, folha e fru-to). Os teores de compostos fenólicos totais determinados pelo método de Folin-Ciocalteau, foi de 19,3 para a raiz, 114,0 caule, 115,0 folha e 31,0 para o fruto, ex-pressos em equivalente de ácido gálico / grama de amostra. O teor de proantociani-dinas foi de 1,9 para a raiz, 7,6 caule, 17,3 folha e 2,1 para o fruto em equivalentes de catequina/grama de amostra. A atividade antioxidante foi avaliada pelo o método de seqüestro de radical livre 2,2 difenil-1-picrilhidrazil (DPPH). Os valores de CE50 encontrados para os extratos metanólicos foram: fruto 56,6 μg/mL, folha 6,6 μg/mL, caule 7,4 μg/mL e para a raiz 8,0 μg/mL. Os resultados mostraram que C. pubes-cens é uma boa fonte natural de antioxidantes. Os óleos essenciais foram analisa-dos por CG/EM. Os principais compostos identificados na raiz foram Biciclogerma-creno, Espatulenol, Germacreno-D e Viridiflorol, ao passo que, para o óleo essencial do caule, foram identificados como principais o Eucaliptol, Espatulenol e Bicicloger-macreno. O óleo essencial dos frutos contém aproximadamente 80% de monoterpe-nos, destacando-se Limoneno e Eucaliptol. O óleo essencial das folhas é constituído por 55,36% de sesquiterpenos e os componentes principais são Biciclogermacreno, Germacreno-D e Eucaliptol. Os óleos essenciais apresentaram atividade antimicro-biana contra bactérias Gram-positiva e Gram-negativa testadas, e estes resultados podem levar a uma alternativa para o controle de bactérias em doenças bucais.

This work reports the theoretical study of the mechanism of polymerization of 3-hydroxyphenylacetic acids (3-HPA) and 3-hydroxybenzoic acid (3-HBA) and characterization of polymeric material obtained in the electropolymerization of 3-HBA.From the molecular modeling of 3-HPA and intermediates, analysis of the properties derived from the electronic structure, it was possible to propose a mechanism for the electropolymerization reaction. Carbon-6 presents the higher increase in the amount of partial charge, through the processes of 3-HPA oxidation to form cr3-HPA deprotonation followed by this lead to the r3-HPA. The pairing should occur between the SOMO beta of cr3-HPA and SOMO alpha r3-HPA forming the ether bond observed in the experimental IR. We also investigated the electropolymerization of 3-HBA in three different pH values (0.5, 7.0, 12), and you can see that in an acid medium the formation of electrochemically active material is more evident. The study of electrical properties by cyclic voltammetry utlize cationic and anionic probes revealed that the film formed has anionic structure. The 3-HBA and poly (3-HBA) were characterized by spectroscopic techniques (FTIR, UV/Vis, fluorescence), thermal analysis (TGA and DTA) and structural analysis (DRX and MEV). The FTIR spectra showed that the functional groups are preserved in the polymer structure and also highlights the emergence of the ether group in the polymer structure. The analysis of UV/Vis revealed a band broadening and increased extent of absorption of the polymer in the visible region, indicating the extent of conjugation in the polymer structure. The diffractograms obtained for the monomer and polymer are characteristic of crystalline structures. Based on the studies of the electronic structure of 3-HBA and intermediaries, a mechanism for the electropolymerization reaction was proposed, in which the carbon 6, similarly to 3-HPA, should be attacked and the pairing should occur between the SOMO beta of cr3-HBA with the SOMO alpha r3-HBA, the lower energy gap, forming a polyether as elucidated in the FTIR spectra. The propagation of the reaction occurs through the pairing of radicals from the oxidation and deprotonation of the monomer with cation radicals from oxidation of the oligomers formed.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

The calorific value of sewage sludge produced in treatment plant STP Uberabinha was determined in this work, in order to evaluate its potential energy and thus point the possibility of using this biomass as fuel, plus the fact of this use contribute to solution the problem of disposal of this solid in the environment. Obtained by anaerobic digestion, followed by dewatering in centrifugal this material are destined for the municipal landifill of the city of Uberlândia-MG. As the quantities of sludge generated have been increasing in recent years, the physical chemical characterization of this waste is the first step for its energy use, leading to an environmentally conscious management. Thus thermal analysis, including thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimeter (DSC) in nitrogen atmosphere, analysis of the content of carbon, beyond Fourier transform infrared spectroscopy (FTIR) of the sludge, to knowledge of the main groups organic and inorganic present in material, were performed. The experimental results indicated a accentuated exotherm in the DTA curve around 450°C, characteristic of the decomposition of carbon refractory, and enthalpy content 2,4 time that of the first exotherm located at 302°C. Calorimeter analysis revealed a higher calorific value of anaerobically digested sludge equal to 16,2 MJ.kg-1 which compares favorably with values previously reported in the literature for other sludge generated in sewage treatment plants sewage domestic. In addition, the calorific value for this sludge proved to be of the same order of magnitude of the energy potential of biomass as wet wood or even superior to other biomass used for energy generation such as sugar cane bagasse into briquette, with the possibility better performance when its use as fuel. This residue also presented relationship volatile solids /total solids (VS/TS) 65%, and almost entirely in front of the total organic carbon content of total carbon, contributing positively to the energy use of its combustion.