Repositório RCAAP

The degradation/mineralization of vinasse with electrochemical generated ozone was investigated using a solid polymer based reactor (Ti/b-PbO2/Nafion 111/steel 316). Ozonization was done at the natural pH (~4)of the vinasse as well as after changing the pH to 12. Degradation/mineralization was followed using uv-visible spectroscopy, chemical oxygen demand, COD, and total organic carbon, TOC, measurements. A current density of 0,15 A cm-2 was applied, resulting a 6,21% current efficiency furnishing a real ozone charge of 1,55 g h-1. After 10 h ozonization a significant decolorization of the vinasse was observed. The reduction in COD and TOC-values observed was somewhat higher under basic conditions. The vinasse oxidation mechanism by ozone is rather complex and can occur by direct molecular O3 or indirectly by OH generated through O3 decomposition. The high TOCvalues when compared with the spectrophotometric data suggest ozone is capable of destroying the parts of the organic structure responsible for the color. However, the ozonization did not mineralize a significant fraction of the aromatic structure as supported by the remaining absorbance in the uv-region after a 10 h ozonization period. The g (=COD/TOC) parameter suggests an increase in the vinasse biodegradability. Preliminary results after sedimentation and filtration of the degraded vinasse show this simple procedures are capable to significantly reduce almost all of the physico-chemical parameters of vinasse.

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This research aimed at understanding and analyzing the meanings and significances attributed by secondary school teachers to legal documents that guide the teaching of chemistry in high school. To do that, the work was exploited, from the legal guidings, the possible contradictions that there are in the implementation of education policies and, to a certain extent, these documents favor or create barriers to promote the changes in the school context. This research was anchored in historical and cultural theory of Vygotsky (1989, 1995, 2001). This study has qualitative character, which used semi-structured interview as a source of data collection that was conducted with secondary school chemistry teachers, who work in Stateowned school in a city of Triângulo Mineiro . The interviews were audio-recorded and accompanied by notes. Then they were heard and transcribed. The research results showed that most respondents did not know the legal guidings for secondary school deeply. Thus, the proposed reforms to education published in the legal guidings were not appropriate, they remain strange and little understood by teachers. However, teachers demonstrated, even modestly, be on a par of the discussions related to interdisciplinarity and contextualization. However, several obstacles were encountered to put these practices into action, such as work overload, lack of material resources, inappropriate physical infrastructure of schools, not enough number of classes per group, ill-prepared and insecure teachers; concern about fulfilling the curricular content proposed by legal guidings, inappropriate textbooks, lack of autonomy of teachers, repression and control of power by school administrators, the depreciation of the teacher, the discredit of the government's proposals, among others. The way teachers express themselves made it possible to understand the discouragement, hopelessness and degradation experienced by these professionals. By doing so, it was concluded that there is a rupture between meaning and significance of teaching activity, which makes the work of these professionals empty of meanings. This is due to the distance between what is proposed in the legal documents and school reality. This distance may decrease when educational policies involve the teachers both in the preparation and implementation of proposals for curriculum innovation.

In recent years different research groups are trying to find a regularity between the chemical analysis and various types of coffees selected through tasting. Besides the coffee beams selected for drinks that are most appreciated ( soft , gourmet, hard ) coffee husk are not discarded and much used by the roasted company. The add of roasted coffee husk (30-50%) allows the reduction of costs of coffee sold in the domestic market and are therefore routinely used in the composition of our daily coffee. This study aimed to examine and quantify the chemical constituents of coffee husk named mellow (bark of Coffea Arabica, without parchment, cultivar Mundo Novo) subjected to medium roasting, from Cerrado Mineiro. Although other studies are found in literature on the chemical composition of coffee husks there is not any scientific work that brings a detailed analysis of the chemical constituents of the shell (epicarp) and a comparison with the coffee (Coffea arabica). Thus, the analysis of macromolecular chemical composition of coffee husk by wet analysis, by spectroscopy in the ultraviolet (UV), by high performance liquid chromatography (HPLC) and by chemical composition of volatiles (mass spectrometry, MS) were made in comparision to that of coffee. Additionally, and viewing to a possible application of the bark of coffee in the coffee culture, it was studied its allelopathic action: the phytotoxic activity of dichloromethane extracts in pre-and post-emergent [germination of Panicum maximum (capim colonião)] treatment on growth of root and shoot, and analysis of secondary metabolites present in the dichloromethane extract of the bark of coffee. Chemical analysis of the roasted coffee husk revealed a well differentiated composition of roasted coffee bean. The results coming from insoluble solids (66.03% for coffee, 55.38% for coffee rusk) and aqueous extract (34.41% for coffee, 39, 46% for coffee rusk) of activity may suggest a taste very close, which explains the addition of the powdered coffee rusk of the coffee trade. Significant changes occurred in levels of all studied parameters: humidity (3.0% for coffee, 3.0% coffee rusk k), insoluble solids (66.03% for coffee, 55.38% for coffee rusk), aqueous extract (34.41% for coffee, 39, 46% for coffee rusk), the lipid content (11.62% for coffee, 4.52% for coffee rusk), Klason lignin (33.50% for coffee, 13.23% for coffee rusk), holocellulose (47.19% for coffee, 32.15% for coffee rusk), extractives methanol / water (34.41% for coffee, 39.46% for coffee rusk), phenolic compounds (75.99 mg mg-1 for coffee, 23.63 mg mg-1 for the coffee rusk), proanthocyanidins (16.52 mg mg-1 for coffee, 21.97 mg mg-1 for the shell), pH (5.23 for coffee, 4.21 for coffee rusk), caffeine (3.85% for coffee, 0.81% for coffee rusk l) and antioxidant activity (EC50 1,10 mg mg-1 of DPPH and coffee, 6,41 mg mg-1 of DPPH for coffee rusk), By presenting some compositions below the coffee beans (except lipid contents), the coffee husk has chemical characteristics undesirable for consumption. Evaluation of allelopathy in dichloromethane extracts of coffee husk, showed that the secondary metabolites were effective in inhibiting the development of the root (at a concentration of 100 mg mL-1), while inhibiting the development of the shoot allelopathy, the extract of coffee grounds was more efficient (at a concentration of 100 and 200 mg mL -1), a significant inhibition in the growth of roots and shoots of the weed Panicum maximum (capim colonião). Anyway, these results suggest the use of coffee husk as an adjunct to control weeds.

With the increase in biodiesel production, it is expected that large quantities of glycerol are available on the market at reasonable prices. It is moreover relevant and promising to search for processes that lead to the glycerol value-added products. Furthermore, glycerol is considered one of the 12 key molecules most promising for use in future bio-refineries. In this sense, this dissertation aimed to contribute to a better understanding of the reaction of steam reforming of glycerol using platinum catalysts supported on carbon. This system has been used lately as an excellent provider of synthesis gas at low temperatures, which, integrated with other catalytic systems, can produce hydrogen (with WGS) and fuel (to SFT) in a single reactor. In this thesis, we evaluated the effect of particle size of platinum and the pH of the feed solution in the reaction of steam reforming of glycerol. For this study, we used commercial catalysts BASF (E-Tek) supported on carbon (Vulcan X-72), containing 5,0, 10,0 and 20,0% by weight of Pt catalysts containing 0,5, 1,0, 2,0 and 3,0% by weight of Pt, supported the same type of carbon, but prepared in the laboratory, via dry impregnation of aqueous solution of hexacloroplatinium followed by drying at 120 ° C for 12 hours. The prepared and commercial catalysts were characterized by the technique of volumetric chemisorption of CO to obtain the number of active sites available, dispersion and average size of the metal particle. For this characterization, the catalysts were activated using the same procedure that is done before the catalytic tests, or raising the temperature to 1°C/min to 350°C under a flow of ultra pure H2, staying in for 2 hours. These catalysts were evaluated for the reforming reactions of glycerol gas at atmospheric pressure, varying the reaction temperature (275-350 °C), the mean residence time (WHSV = 33, 66, 99 min-1) and pH of the aqueous solution glycerol (30% by weight) of food. The pH was modified, reaching values of 3 and 10, adding acid (HNO3) or base (NH4OH) compounds, respectively, in aqueous, near neutral (pH = 6,5) of 30% by weight of glycerol. The results showed that the reaction of hydrogenolysis of glycerol is sensitive to the structure, both for activity and for selectivity. In other words, the reaction rate and selectivity to products of degradation / decomposition (breaks C C bonds), mainly synthesis gas, increased with the size of the metal particle. While, acetol, product formed by the breakup of the preferential binding C O (via dehydration) for C C, is preferentially formed when small particles are present. The catalytic tests for the change in pH of the solution proved to be more selective gas (CO) in basic medium. Alongside the formation of CO, we observed the production of acetol was favored in several situations: in flow (WHSV) high and / or conversions and low in acid, by adding inorganic acid. The lower the temperature of reaction, less carbon monoxide and more acetol are formed. This trend of decrease of CO selectivity was more marked in percentage terms for the reaction in acidic than basic. Furthermore, the increased selectivity to acetol is greater, in percentage terms in basic medium in relation to acid. With these results, a proposed reaction mechanism was presented.

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A polymer derived from 3-hydroxi phenyl acetic acid, poly-(3-HFA) was produced over a graphite electrode in an aqueous acid media through cyclic voltammetry with the intention to form an interface for biomolecule detection for a biosensor development. Cyclic voltammograms show that electropolymerization process begins around +0.9V, with the appearance of an oxidation wave reaching a peak potential at +1.06V. This wave is pointed as being the monomer oxidation for its cation-radical form. With a second cycle there is a current values decrease of this wave and a redox pair waves appears between +0.3 and +0.7V. This pair refers to the redox process of the polymeric film, growing over the electrode surface. As the sweep number increases it is observed a large current values increase of these redox waves, pointing the formation of electroactive material with a low insulating behavior. The electrical properties of this polymer were determined through electrochemical impedance spectroscopy (EIS) and the electrochemical quartz crystal microbalance (EQCM). high frequency and another in low frequency ranges, suggesting the existence of two time constants, which can be confirmed through Bode diagram. This result suggest that the poly-(3- HFA) electrochemical behavior is controlled by kinetic processes in high frequency ranges and by mass transport in low frequency ranges. The obtained result were simulated by a set of physical resistances and capacitances to fit to the experimental data, seeking the better circuit to represent it, which the first time constant is referred to an electronic transference on the electrode surface between the polymer and the solution and the second refers to mass transport processes in poly-(3-HFA) inner layers. For the EQCM result, it is observed that the charge/frequency profile present a linear behavior, namely, a rigid film is being deposited over the electrode surface and the Sauerbrey equation is valid for the mass calculus. It is observed that, on the first cycle, the mass values remained constant until around +0.9V, exactly where the electropolymerization process begins. After 1.0V, the monomer, reaching its oxidation potential, begins to form the cation-radical structures which adsorbs on the electrode proved by the mass values increase. During the reverse potential sweep, there is an additional mass increase due to the part of the monomer oxidation over this range. After this point, a little mass values decrease is observed, however, remaining constant until the end of the cycle.

The present investigation objectified analyzes the limits and possibilities formatted of webquest to introduce the research on teaching formation on chemistry. For so, we started from the research choiced from Demo (1997; 2002) Maldaner (2000) and Galiazzi (2003) that pointed, between others characteristics of research job, the new elaboration of knowledge by the allowing that by himself assume how author of your formation, I mean, it´s capable of build knowledge from own initiating, learning how to learn. The investigation occur on discipline context of supervised curricular probation in chemistry IV from a licenciature in chemistry from Itumbiara GO. Opted for one investigation of qualitative kind, ruled on case studying, for develop on natural scene, reach on a descriptive scenery, reach on a descriptive data, focus on process and the variables that interfere on the research way. To catch and register the data were used the questionnaire, recording in audio and camp notes. The analyses shows that the elaboration of webquest become possible the development of capacities ah abilities needed to the research: the search and the new construction of the knowledge. But the academician present difficult to the decisions and dependence to models and standard to be followed. The result indicate the necessity of this abort during the initial formation of the teacher for the same become better your practice on research to your context and become a researcher. The webquest produced were changed, seen that some groups showed bigger interest and dedication, once that the work with the research need a give a bigger time to study and base. How consequence, the webquest sows the meaning potency on research teaching formation to become possible the use of informations available on building of knowledge from an emancipated form. Meanwhile we should detach that this is a process that once mobilized on initial formation, must be extend during all the existence and teacher practice with different formative strategy.

It were studied the allelopathy potential of the extracts of the root, of the stem and of the leaves of Origanum majorana L., as the inhibition of the germination of seeds of Panicum maximum (grass-colonião), the rehearsal was accomplished in boxes gerbox, with light period of 10 hours and 7 days, with solutions of the extracts diclorometânicos of the root, stem and leaf of O. majorana in the concentrations: 50,100 and 200 ppm, as well as it was made the negative rehearsal (white) with Panicum maximum for analysis of the results. The inhibition increased substantially with the increase of the concentration of the extracts, and the extracts of the root, stem and leaf of O. majorana presented inhibition of 100% of the germination in the concentration of 200 ppm. The extract of the root presented inhibition of 80% of the germination in the concentration of 100 ppm and the extract of the leaves of O. majorana presented efficiency of 83% in the inhibition of the root and aerial part, even in the lowest concentration (50 ppm). The extract of the stem was also shown efficient inhibiting 80% of the root and aerial part in the concentration of 100 ppm. Later they were classified the present secondary metabólitos in the root, stem and leaves, of the species in study for thin layer chromatography (TLC), in the root were identifying: flavonoids, triterpenes, steroids and polyphenols. In leaves and stems were identifying: flavonoids, anthraquinone anglicones, triterpenes, steroids, tanines and polyphenols. The active extracts were analyzing through gas chromatography coupled mass spectrum, identifying: beta-farnesene, delta-decalactone and lactone of acid 5-hidroxy- 2-decenoic.

The cellulose of sugarcane bagasse was chemically modified for producing cellulose sulfate acetate, which was tested as an additive in mortars of Portland cement (CPV ARI) in the civil construction. The material was produced by simultaneous acetylation and sulfonation, and besides cellulose sulfate acetate, two byproducts were generated, which presented different solubility in water. The obtained materials had been characterized by Infrared spectroscopy (IV), and revealed that only one of the derivatives showed the characteristic band of sulfate groups (807 cm-1) in the infrared spectrum, which was cellulose sulfate acetate. This material was then characterized by determination of the degree of substitution of acetyl groups by chemical route (DSacetyl), determination of the degree of substitution of sulfate groups (DSsulf) by Elemental Analysis, Nuclear Magnetic Resonance (13C-NMR), X-ray Diffraction, determination of reduced viscosity and Thermogravimetric Analysis (TGA). The results have shown that the cellulose derivative showed a DSacet of 2.7 and DSsulf of 0.063. Compared to the 13C-NMR spectrum of cellulose acetate (derivative that occurs only in the incorporation of acetyl groups), the presence of sulfate groups in the sample of cellulose sulfate acetate shifted the position of C6 peak for lower field in 13CNMR spectrum, due to not shield carbon caused by the incorporation of electronegative groups. According to the diffractogram obtained to the cellulose sulfate acetate, it appears that the sample sulfoacetylated presents an X-ray diffraction pattern mainly amorphous, mainly due to the presence of a pronounced halo at about 2θ = 22 °. By measuring the reduced viscosity of the solution of cellulose sulfate acetate, it was found that the presence of ionic sulfate groups in the sample is the causes to reduced viscosity increase to more dilute concentrations (below 1 mg/mL). In the synthesis of cellulose sulfate acetate is produced a polyelectrolyte that due to the presence of sulfonic groupsmay be able to act as an additive for mortars in the construction industry due to its high solubility in water. The evaluation of cellulose sulfoacetate as additive to mortars was based on results of fluidity, mechanical strength to compression of hardened mortar and potential resistance of adhesion strength. The best results were obtained for the polymer/cement ratio of 0.60% with which it was achieved an increase of 13.80% in consistency and 21.05% on the potential resistance of adhesion strength, while the strength to compression remained nearly constant compared to the reference without additive. Then, it was possible to synthesize the sulfate cellulose acetate obtained from sugarcane bagasse and apply it as additive for mortars in civil construction.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Universidade Federal de Uberlândia

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Poly(vinyl chloride) (PVC) pipes were chemically modified aiming at the production of a sulfonated polymer, using dehydrochlorinated PVC samples as intermediates. Two intermediates were formed: (1) partially dehydrochlorinated PVC with long sequences of conjugated double bonds and (2) the product of partial dehydrochlorination of PVC and nucleophilic substitution of chlorine by hydroxyl groups. The infrared spectra showed that dehydrochlorinated samples are heterogeneous materials, showing different proportions of elimination products, hydroxyl substitution and partial oxidation. Samples dehydrochlorinated with PEG 400 (DPVCA) for 24 hours and PEG 400 for 15 minutes (DPVCD) showed the highest sulfonation yield, what is related to the sulfonation mechanism occurring predominantly due to the presence of hydroxyl groups in a mixture of vinyl alcohol and vinyl chloride units. The sulfonation was confirmed by the presence of a medium intensity band at 1180 cm-1 assigned to sulfonic groups. Both materials showed ion exchange properties but DPVCD is a more promissory material due the value obtained 1.125 mmols/g. These results show that the discarded PVC can be modified chemically to produce a new material with new perspectives to the work as ion exchanger.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

In this study, a methodology was developed for removal of copper in hydrated ethanol fuel, using baru almonds (Dypterix alata). To investigate the adsorption capacity of baru almonds, studies were accomplished being varied the type of chemical treatment, strip sizes, time of contact, and pH of the solution, seeking the construction of adsorption isotherms and the determination of ideal conditions of the process, using as working solution the hydrated ethanol fuel sample acquired in a local fuel station. Different techniques were applied for the characterization of the material such as thermogravimetric analysis (TGA), superficial charge of the material (pHpcz), and Fourier-transformed infrared spectroscopy (FT-IR). TGA results indicated that almonds after acid treatment presented larger thermal degradation when compared with in natura almonds. The pHpcz of in natura and acid-treated almonds were 6.85 and 4.10, respectively. The confirmation of the functional groups of the acid-treated almonds by FT-IR suggests the presence of proteins, fatty acids, carbohydrates, and lipids. The largest capacity of copper removal was observed for the following conditions: treatment with 0.5 mol L-1 HNO3, granulometry range from 250 to 500 μm, 45 minutes as contact time, and pH solution at 7.0. Data of copper removal were adjusted to Langmuir and Freundlich models. The Langmuir parameters were qmax (mg g-1) of 5.80 and b (L mg-1) of 0.1013, and Freundlich parameters were Kf (L mg-1) of 0.753 and 1/n of 0.474. Tests for copper removal applied in commercial samples of hydrated ethanol fuel presented satisfactory results, with an average removal value of 92.60% for the initial concentration (spiked) of 25.00 mg L-1 of Cu(II) in the samples.

Electrochemically generated ozone was applied on degradation of the herbicide 2,4- dichlorophenoxyacetic acid (2,4-D), in acid and alkaline solutions, under semi-batch condition using a column bubble reactor. Oxidation of 2,4-D was studied using different experimental approaches in order to assess the oxidative process (degradation and partial mineralization) from different points of view. Structural changes of 2,4-D during ozonation were quantified monitoring the decrease of the integrated absorbance (190-310 nm) while its conversion in ozonation by-products and/or mineral substances was quantified using the Gas Chromatography (GC) and Total Organic Carbon (TOC) techniques. Measurements of TOC and Chemical Oxygen Demand (COD) revealed that only a small amount of 2,4-D was mineralized during ozonation. Also verified is that alkaline conditions resulted in a more rapid removal and/or degradation of 2,4-D. Pseudo-first order kinetics was used in order to determine the different rate constants obtained for degradation of 2,4-D. Oxidation susceptibility of the organic matter measured through the COD/TOC ratio revealed that ozonation (acid and alkaline conditions) can lead to a reduction in the recalcitrance nature of the degraded organic matter in comparison with the parental compound (2,4-D).

In this original work, the specie Maclura tinctoria (L.) D. Don Ex Steud, as known as amoreira , was evaluated under many aspects. The macromolecular constituent s composition, the phenolic compounds level, antioxidant and antimicrobial activity of the bark and wood were studied. The corresponding percents of total extractives level, acid insoluble lignin (Klason´s lignin), acid soluble lignin, holocelluloses, hemicelluloses and α-celluloses were an average of the values for the wood: 10.79 ± 1.98; 21.47 ± 1.25; 1.28 ± 0,00; 69.43 ± 2.16; 23.59 ± 0.36; 46.02 ± 1.53 (%), and for the bark 50.64 ± 2.47; 18.77 ± 1.20; 0.45 ± 0.01; 29.14 ± 1.90; 8.78 ± 0.42 and 21.4 ± 0,77 (%). The level of total phenols obtained with methanol/water 4:1 (v/v) and acetone/water 7:3 (v/v) extracts using Folin-Ciocalteau method for the wood was 38.43 ± 0.42 and 45.34 ± 0.86 and 35.03 ± 0.94 e 43.17 ± 1.18 for the bark, expressed in Gallic acid equivalents (GAC) per gram of sample. The proanthocyanidins level obtained was 5.11± 0.59 for wood and 6.51 ± 0.62 for bark, in catechin equivalents per gram of sample. The antioxidant activity was determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) for the wood and bark extracts, with IC50=18.74 and IC50 = 20.97 μg mL-1 , for wood and bark, respectively. The crude extracts from wood and bark from Maclura tinctoria (L.) has presented growth inhibition of the tested periodontopathogenic bacteria. The MIC of the crude extracts were in the range of 200 and 400 μg mL-1 for wood extracts and from 20 to 400 μg mL-1 for bark extracts, against the control microorganisms tested.

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This work describes the development of analytical methodology for Zn(II) determination in alcoholic matrices with significance to alcohol fuel and sugar cane spirits samples, using flow injection (FI) preconcentration systems and flame atomic absorption spectrometry (FAAS). The flow manifold was made up of a peristaltic pump, four three-way solenoid valves and a minicolumn packed with the coal obtained from Moringa oleifera husks. Middle Infrared Spectroscopy, Thermogravimetric Analysis and X-ray Diffraction were used to characterize the biosorbent in order to identify the main groups responsible for interaction zinc ions, and to evaluate the thermal stability of material. The construction of adsorption isotherms was used in order to identify the mechanisms involved between the material and the Zn2+. Chemical and flow variables and the effect of concomitant ions were studied in the proposed procedures, using multivariate methods. A full factorial design (24) and response surface were used to identify the variables that influence the adsorption system. The results were: sample flow rate 4.0 mL min-1, eluent concentration of 1.0 mol L-1, adsorbent mass equal to 30.0 mg and sample initial pH 4.0.The accuracy of the proposed method was evaluated by recovery test applied in the samples, and also by comparing the analytical performance using commercial adsorbents. The proposed methodology was successfully applied for Zn2+ determination in alcohol fuel samples and sugar cane spirits were found recovery to 100%.