Resumo em Inglês:Biodiesel is a biofuel produced by the esterification reaction. It is an option to replace fossil fuels, mainly diesel, due to its similar physical and chemical properties. In this research, a mathematical modeling was performed to predict the antioxidant mass to be added in a commercial biodiesel to achieve the minimum oxidative stability provided by the legislation. An equation for each additive was proposed, with the mass of these antioxidants considered as dependent variables and the conformity parameters as independent ones, obtaining multiple regression equations without intercept. The BHA and BHT antioxidants were used. The equations provided were lower at the 5% level and presented determination coefficients (R2) equal to 0.9790 and 0.9770 for the BHA and BHT, respectively, proving their predictability ability and also showing that they can be used to estimate the antioxidant mass to be added in a biodiesel to reach the current regulations.
Resumo em Inglês:Pervaporation requires operation at mild temperatures and provides low energy consumption, which makes this technology economically attractive. However, pervaporation is not yet a widespread process in the industry. One of the justifications is the complexity in the quantification of variables related to the membrane in the most diverse conditions. This factor results in the absence of generic models in the simulation software. This work aims at the rigorous phenomenological modeling of a pervaporation process using a polyetherimide membrane intended for the dehydration of ethanol. The model was developed on the Aspen Custom Modeler™ platform. Two approaches were implemented and compared: PERKAT and PERVAP models, being the last one the best model. The main variables of the process were evaluated. It was possible to verify the capacity of separation of the pervaporation module in breaking the barriers of the azeotrope, reaching a product with a high level of purity in ethanol, and recovery of up to 99.8%. In addition, the generic PERVAP model was exported to Aspen Plus™ and a cascade pervaporation unit was simulated. The specific energy consumption was calculated and compared to that of traditional separation processes. A 70% reduction was obtained compared to the most economical distillation configuration.
Resumo em Inglês:Simultaneous analysis of radionuclides in water had not been performed by mass spectrometry of the magnetic sector. Some international organizations indicate that it is necessary to know the contamination of drinking-water, including radioactive aspects. The novelty of this study was to determine simultaneously radioisotope radium, thorium, uranium and lead stable. Experiments were performed in an accredited laboratory (International Organization for Standardization/International Electrotechnical Commission-7025:2005). The radionuclides of thorium, uranium and some of their descendants were obtained. The reported values are in the range of 7E-7-24.28 µg L-1. Their presence decreases in the order thorium>uranium>radium in drinking water and uranium>thorium>radium in seawater. These results do not represent any risk to the population because very low concentrations were determined.
Resumo em Português:The objective of this work was to control the purity level of canephora coffees (Conilon coffee) from the state of Espírito Santo (Brazil), as a function of the addition of grounds produced by the coffees themselves using a portable microspectrometer in the infrared region. (microNIR), associated with chemometric tools. The PCA model grouped the coffees according to the level of adulterant in the samples and showed that the presence of moisture and polysaccharides is important for the discrimination between pure and adulterated samples. PLS-DA and SIMCA classification models were built with commercial samples and resulted in the discrimination of authentic and non-authentic samples with accuracy values above 90% and 82% for PLS-DA and SIMCA, respectively. The quantification results presented by the PLS model were satisfactory for all models, reaching the best results at 75 °C with RMSEP values of 6.13 wt%, R2p = 0.9917; and LOD in the range of 5.6-8.9 wt%; LOQ = 17-26.8 wt%, according to IUPAC; relative standard deviation for repeatability of 1.0 and 1.7 wt%; and intermediate precision of 3.4 and 1.1 wt% for low (<10 wt%) and high (≈ 90 wt%) levels of adulterants, respectively. Therefore, this work represents the first exploratory study to analyze adulterations with coffee grounds by portable NIR, demonstrating the potential of the equipment against this type of adulteration.
Resumo em Inglês:One of the recurrent problems of the agroindustry sector is the incorrect disposal of waste because of the complexity of the material, moisture, among other factors. Waste is not used in tonnage, but is systematically used. Examples of residues are malt bagasse and cassava peel, produced in large quantities in the brewing industry and flour production, respectively. In this context, the objective of this study was to evaluate bioactive compounds of flours produced from agroindustry waste to potentiate their use as an ingredient rich in antioxidants. The flours produced from agroindustry waste were evaluated for phenolic compounds, total carotenoids, antioxidant activity, and the attainment of phenolic profiles and fingerprints by paper spray mass spectrometry. It was possible to identify a broad class of compounds in both flours, such as phenolic acids, flavonoids, among others. The flours can be possibly included in food commodities or packaging formulation since they are natural antioxidants, thus adding value to these products and reducing environmental issues. However, further analysis is needed to ensure bioavailability as well as food safety.
Resumo em Português:Electrocoagulation-electroflotation (EC) technology is a well-known wastewater treatment process that consists of applying electric current to remove contaminants without requiring the addition of chemicals that can generate secondary pollutants. Once they are the most widely used, iron and aluminum electrodes are considered conventional, however they leave unwanted residues, which will give a yellowish-brown color to the treated water, in the case of iron electrodes, and are associated with potential risks to human health, in the case of aluminum electrodes. In this regard, the study of non-conventional electrodes capable of circumventing those problems is essential for the development of more effective wastewater treatments. In this review article, a brief presentation will be made of the history of electrofloculation followed by a brief discussion of conventional electrodes and the mechanisms that govern the processes of removing contaminants by the electrocoagulation process. Subsequently, the non-conventional electrodes reported in the literature up to the present moment will be presented, as well as their potential, applications and performance when applied in water treatment. Finally, will be discussed the coupling of the electroflotation with other water treatment techniques towards achieving a better-quality reuse water.
Resumo em Português:Natural formulations have attracted great interest of many researchers regarding their use as latent fingermark developers powders due their important characteristics as the presence of natural pigments in these materials that offer a good contrast on the applied surface and also luminescent properties, which facilitates the visualization of minutiae in problematic substrates such as multicolored surfaces. In addition, natural powders present low toxicity, are widely available and economically viable. In this sense, the present work addresses the application of several natural products to enhance fingermarks visualization. The natural products were obtained from various sources such as seaweed, spices as well as other sources such as terrestrial and herbaceous plants. The evaluated powders are composed by compounds as chlorophyll, phycocyanins, curcumins, lawsone, fatty acids, coumarins, flavonoids and terpenes. These powders showed good adhesion to latent fingermarks, with similar or superior efficiency to the available powders on different surfaces with clear visualization of the minutiae. The development of new powders applicable to papiloscopy are extremely important since the conventional available powders, besides being expensive, are imported and within the national context there is a great lack of these revealing materials within forensic investigations by the Federal Police and in laboratories of research.
Resumo em Português:Alzheimer’s disease has about 9.9 million new cases annually, according to World Health Organization. Due to the increasing incidence of people affected by AD and the absence of an efficient treatment or cure so far, many researchers worldwide are involved in the search for novel promising drugs candidates, through several targets, exploring distinct structural patterns. In this context, we describe herein, focusing the last 20 years, strategic examples of substances with targets related to Alzheimer’s disease derived from natural products, such as alkaloids, chalcones, coumarins and flavonoids, in addition to carbamates and heterocyclic compounds. Furthermore, some cases are discussed where computational chemistry is used to better understand protein-ligand interactions.
Resumo em Português:Mass spectrometry (MS) is a high-performance analytical technique that allows a measurement of the mass/charge (m/z) ratio of compounds present in a sample. MS is able to separate two m/z ions with determined values (mass resolution), being an important characteristic, especially in the analysis of biochemical components and complex mixtures. Mass analyzers define the resolving power and accuracy of different types of mass spectrometers. Herein, the performance of two mass analyzers (Fourier Transform Ion Cyclotronic Resonance (FT-ICR) and quadrupole ion trap (LTQ)) was tested on low (Mw = 165-679 Da) and high (Mw = 783-8.58 kDa) molecular weight molecules (Phenacetin, Procaine, Benzocaine, Caffeine anhydrous, Lidocaine, two metal porphyrin standards, the first cobalt and the second vanadium, and two protein standards, Ubiquitin and Beauvericin), and finally, for an oil sample. LTQ-MS and FT-ICR-MS had similar performance and high reproducibility. However, the mass accuracy and resolution power of the FT-ICR (error lower than 5 ppm and RP higher than 400,000) was higher, being therefore, it was more suitable for the analysis of proteins and oil, for instance. On the other hand, the CID analysis via LTQ demonstrated its applicability in fragmentation experiments, being able to determinate the chemical connectivity of organic compounds in non-complex mixtures.
Resumo em Português:The student who has just entered higher education is faced with chemical knowledge that receives a much deeper treatment when compared to high school so that he is not always able to construct meanings for this knowledge. To help in this construction of meanings, we analyzed an experience in which students of an Inorganic Chemistry course were asked to produce a text based on the reading of a scientific divulgation text and to participate in the evaluation process of their colleagues’ texts. We observed a good involvement with the activity and the construction of relationships between the topic in question and the contents developed in the discipline, what contributed to improve the performance of the class. We argue that the involvement with creative writing of scientific texts should be encouraged throughout the entire undergraduate course.
Resumo em Português:Currently, there is a great diffusion of Digital Technologies of Information and Communication (DICT) in society in general and in schools in particular. Thus, the objective of this work was to investigate knowledge explained by 13 undergraduates in Chemistry, in the development of a training process in a given curricular component, about the articulation between experimental activities and DICT in Chemistry Teaching that can be characterized as constituents of a real effective and of a maximum possible consciousness, in order to identify possible learning. As a source of qualitative information, a portfolio produced by the undergraduates during the curricular component is constituted. This portfolio was submitted to the Discursive Textual Analysis procedures. The analyses, based on the progressive theoretical framework of the Brazilian educator Paulo Freire, pointed to different levels of awareness regarding the experimental activities linked to the DICT. For example, the undergraduates explained knowledge that questioned the use of DICT articulated with experimental activities as a way to unconditionally promote student learning. This was interpreted, to some extent, as a collaboration of the formative process adopted in a dialogical-problematizing approach.
Resumo em Português:After extracting practically all the gold and diamonds from the captaincy of Minas Gerais, Brazilian and foreign politicians and naturalists were looking for new sources of wealth in the form of ores. However, the news of the discovery of copper and cobalt mineral deposits, made by José Vieira Couto (a naturalist from the city of Diamantina), were discredited because the locations indicated or even the analysis performed may have been done incorrectly or even intentionally altered by the naturalist in order to draw the attention of the Portuguese Crown or seeking ways of obtaining social and political promotion among the colony’s governors.
Resumo em Português:Considering the bicentenary of Brazil’s Independence in 2022 and that this year was proclaimed by UNESCO as the International Year of Basic Sciences for Sustainable Development, in mid-2021 the Brazilian Chemical Society (SBQ) launched the “Post 2022 Chemistry Movement - Sustainability and Sovereignty”, with the main goal of promoting different activities so that chemistry contributes for the sustainable development and sovereignty of Brazil in the coming years. One of these activities is the proposal of an action plan, with goals to be achieved by 2030 and 2050. This article describes in detail how this action plan was formulated by a working group, with the help of an advisory council and interviews of 18 professionals from universities, the government, industries, the third sector and other organizations. Mimicking the Agenda 2030 SDGs, the resulting action plan is based on two broad Chemistry Sustainable Development Goals: promoting sustainability through chemistry in basic education, and promoting sustainability in the industry and university through science, technology, innovation, and education (STI&E) in chemistry. After the definition of three driving technological challenges in STI&E, they shall be successively implemented through different actions starting in 2023 yet.