Abstract in Portuguese:Application of adsorbents derived from waste in contaminated areas remediation is aligned with sustainable development goals and circular economy principles. As chemical activation can result in increased adsorption capacity, it is an alternative to improve the performance of materials and enable their use. This study evaluated whether activated compost derived from the organic fraction of municipal solid waste would be an efficient and low-cost adsorbent. Chemical activation was performed by impregnating 1 mol L-1 of phosphoric acid for 12 h at 25 °C. Characterization and batch equilibrium tests were carried out to confirm if chemical activation would positively affect the retention of lead (Pb) and cadmium (Cd). Surface functional groups and minerals were verified through Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffractometry (XRD) before and after batch equilibrium test. Removal percentages ranged from 52.49 to 91.22% for Pb (initial concentrations of 20.11 to 889.20 mg L-1) and from 13.33 to 87.13% for Cd (initial concentrations from 1.56 to 667.50 mg L-1). Compared to the original material, activation did not increase Cd adsorption capacity. However, was observed an improvement in adsorption performance for Pb between 76.86 and 443.30 mg L-1. The Langmuir isotherm best fitted the experimental data obtained both for Pb and Cd.
Abstract in English:The morphology and adhesion strength of the autocatalytic electroless nickel phosphorus (Ni-P) film, deposited at 40 ºC on polished alumina (Al2O3 99.6%) substrate, pretreated by sulfur/nitric solution, sensitizing with acid stannous chloride and activated using palladium chloride solutions, was studied using contact angle (CA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), mechanical profilometer (DekTak), and direct laser writer (“maskless lithography”). The results showed that after treatment of the polished Al2O3 substrate, it presented a high performance in the electroless deposition of Ni-P thin-film at low temperature (40 ºC). It was obtained a more compact and continuous film, with small grain size and strong adherence.
Abstract in English:The objective of this study was to develop two simple and selective visible spectrophotometric methods for the determination of antihistamine drug triprolidine hydrochloride (TRH) in the capsules. The methods were based on the formation of ion-pair complexes between TRH and two dyes, namely, bromocresol green (BCG) and bromophenol blue (BPB). The produced ion-pair complexes were measured at 415 and 410 nm for BCG and BPB methods, respectively. Beer’s law was applicable in the concentration ranges of 2.50-15.0 μg mL-1 TRH for both methods. The molar absorptivity values were found to be 2.12 × 104 and 2.07 × 104 L mol-1 cm-1 for the BCG method and BPB method, respectively, and the Sandell’s sensitivity values were 0.0149 and 0.0152 μg cm-2. The limits of detection and quantification were calculated and found to be 0.29 and 0.86 μg mL-1 for the BCG method and 0.31 and 0.95 μg mL-1 for the BPB method. The methods were applied successfully for TRH determination in bulk drug and in the capsules.
Abstract in English:The current study was undertaken to immobilize Kluveromyces lactis β-galactosidase on alginate coated magnesium oxide nanoparticles (ACMONPs). Transmission electron microscopy showed that MgO-NPs synthesized by wet chemical approach were of 27 nm size and spherical in shape. Excellent biocompatibility of sodium alginate resulted in 90% immobilization yield for β-galactosidase due to covalent attachment. Soluble and immobilized β-galactosidase exhibited its pH and temperature-optima at pH 7.0 and at 40 °C, respectively. However, the enzyme attached to ACMONPs enhanced its activity at higher and lower pH and temperature ranges, in contrast to enzyme in solution. ACMONPs bound enzyme displayed greater enzyme activity under the effect of galactose mediated product inhibition as well as in reusability experiment. Our study indicated that 88% lactose was hydrolyzed by β-galactosidase immobilized on ACMONPs at 40 °C as compared to 71% by soluble enzyme under identical temperature in controlled batch reactors. Hence, this nanomatrix can find its potential application in continuous packed-bed reactors for obtaining lactose-free dairy products.
Abstract in English:The antioxidant power of eugenol and vitamin C was examined by analyzing the ability of these ligands to bind to the NADPH oxidase protein target and evaluating their bond interactions with critical residues. The results confirm that docked ligands are more stable in the specified active region of 2CDU during a MD simulation of 100 ns and 2CDU protein-ligand interactions with docked ligands showed significant hydrogen bond, hydrophobic, and water bridge formation. Eugenol exhibits hydrogen bond interactions with critical residues in the selective pocket in comparison to vitamin C. Also, eugenol had a similar binding orientation and very considerable stability in the selective pocket of 2CDU with a high binding energy with lipophilic energy. The electrostatic potential maps indicate that for eugenol, the –OH and –OCH3 sites, while that the –OH and –CO functional groups in vitamin C are responsible of the antioxidant activities of these compounds. HAT and SET mechanisms suggest that eugenol may become a better antioxidant than vitamin C.
Abstract in Portuguese:Constantly we have to deal with an exponential increase in the amount of different chemical compounds that industries synthesize and manufacture, such as drugs, pesticides, persistent organic pollutants, preservatives, and personal hygiene products. Many of these chemical substances are biologically active and interact with biomolecules, such as proteins, through specific mechanisms that lead to different biological responses. Due to the inherent risk of many compounds to the environment and to humans, their toxicological activities must be evaluated. In order to evaluate the biological activity of molecules, three types of experiments can be used: in vivo (e.g., animal tests); in vitro (e.g., cell tissue culture); and in silico simulations. In vivo and in vitro experiments are time-consuming and expensive processes, in addition to causing ethical discussions and debates. An alternative to avoid these setbacks is the use of in silico models. The scientific community thus begins to use in silico models as a possible alternative, developing a large number of models and strategies capable of predicting the toxicological properties of several chemical compounds. This review discusses methods that employ in silico models to assess and predict the possible effects of contaminants found in natural waters.
Abstract in Portuguese:Platinum is one of the well-known catalytic materials for which the electro-oxidation of carbon monoxide better behaves as a sensitive reaction to the catalyst surface structure. For the electro-catalytic reactions that behave like this, the rate (faradaic current density) is the result of the sum of the activity of the different active sites working with very different efficiencies or abilities. In this scenario, different atomic arrangements on the catalyst surface are expected to play different roles in surface-catalyzed reactions. In this article, the functionalities that surface defects (steps) can play in the adsorption and electrocatalytic oxidation of CO on model platinum surfaces are reviewed. Surface defects are indirectly related to the up catalysis as well as to the inhibition of reaction pathways of CO electro-oxidation under very particular conditions; these surface entities are also indirectly related to restrictions for the mobility of adsorbed CO on the (111) terraced surfaces. We analyze the selective activation and deactivation of surface sites by the pH effect, and typical catalytic properties of extended surfaces and shaped-controlled nanoparticles have been discussed thoroughly. We present a model of most active sites involved in the pathways of CO2 formation from the electro-oxidation of adsorbed CO.
Abstract in Portuguese:The use of artificial intelligence (AI) in education is a current topic and in Chemistry teaching it has the potential to offer some benefits. This article is the first attempt to show that activities involving Chemistry can be accelerated with the help of AI. This is a propaedeutic study that aimed to analyze the contributions of the ChatGPT AI in defining chemical concepts. The research was conducted in the virtual environment of the chatbot and was carried out in four stages. The results show that ChatGPT can be used in Chemistry teaching as an aid to the teaching and learning process. Additionally, depending on the chemical concept, AI provided coherent answers but could lead students to difficulties in understanding. Finally, the use of ChatGPT in Chemistry teaching needs to be guided by a process of reflection, so that from the AI’s responses, students present critical thinking, the teacher considers it as just another resource in Chemistry teaching, besides other actions that can be developed in Chemistry teaching to ensure that the ChatGPT AI is used ethically and responsibly.
Abstract in English:This work describes the analysis of molecular spectroscopy in the UV/Vis region, as well as the study of transmittance, absorption, and reflectance phenomena in an undergraduate class using an LED (light emitting diodes)-photometer and digital image-based (DIB) method using a smartphone to compare with a benchtop spectrophotometer and literature data employing paired T-test for 95% confidence. The novelties of this work are focused on the use of simple, low-cost, and portable analytical instrumentation, based on an RGB-LED photometer and DIB using a smartphone, for teaching Chemistry to undergraduate classes. Moreover, discussions were held on concepts related to the Beer-Lambert law, spectroscopy, pH, equilibrium shift, and calculation for determining the equilibrium constant and pKa of bromothymol blue, which was used as proof of concept. The advantages are the use of low-cost instrumentation for teaching Chemistry, students’ access to concepts, such as radiation source, photodetector, transmittance calculation from analog data, regulation of the power of the light emitted by the LED, and details to understand the interaction between matter and light were described by undergraduate students in Physics and Chemistry throughout the course of Experiments in Thermodynamic and Chemical Equilibrium. The better understanding of theoretical concepts and the possibility of taking the RGB-LED-photometer and DIB instrumentation to schools, exhibitions, science fairs, and Chemistry teaching meetings were pointed out by students as the main advantages of the instrumentation and methods described.
Abstract in Portuguese:The reflections and data presented and discussed in this text represent a portion of the conclusions after an investigation carried out in a master’s research, whose focus was on understanding the curriculum of the training course for chemistry teachers in effect since 2017/2 at UFRGS. The study reported in this article consists of the analysis of the responses obtained from undergraduates through the application of questionnaires. The emphasized issues concern the structure of the course, its disciplines, didactic procedures, teaching strategies, materials, evaluation forms and other aspects aimed at the contribution of specific, pedagogical, and articulating disciplines in the formation of chemical educators. The results indicate maintenance of a curricular matrix that favors academic content taught in the traditional way, but with the inclusion of disciplines characterized by future teachers as essential to the formation of their teaching identity, pedagogical autonomy, and professional development. In addition, there is a disparity between the didactic procedures followed in the different disciplines, which indicates aspects to be prioritized in future reconfigurations of the curricular matrix.