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Efeito dos modificadores mistos nas propriedades elétricas de vidros CaNaBO avaliado por espectroscopia de impedância

Mon, 04 Nov 2024 00:00:00 GMT

Título: Efeito dos modificadores mistos nas propriedades elétricas de vidros CaNaBO avaliado por espectroscopia de impedância Autor(es): Prado, Esmael Dias Primeiro Orientador: Souza, Seila Rojas De Abstract: Borate glass matrices based on boron oxide have lower melting points than silicate glasses, facilitating their preparation and reducing production costs. Boron oxide forms various structural units, allowing the incorporation of dopants such as rare-earth elements and transition metals, enabling the development of heavy-metal-free materials. The incorporation of ions such as Na+ into glass matrices meets the demand for environmentally friendly and biocompatible alternatives in energy storage technologies. Additionally, the amorphous structure of glasses offers advantages over other electrolytes, including isotropic ionic conductivity and the absence of grain boundary effects typical of ceramics. To evaluate the electrical properties of glass samples formed by boron oxide (B₂O₃) as a network former and modified with calcium oxide (CaO) and sodium oxide (Na2O), compositions of (33.33-x)CaO − xNa2O − 66.67B2O3 with x = 5, 10, 15, 20, 30, and 33 mol% were investigated and designated as CaNaBO-x. X-ray diffraction (XRD), Differential thermal analysis (DTA), UV-Vis spectroscopy, and impedance spectroscopy (IS) were employed. XRD and DTA confirmed the amorphous nature of the samples, while UV-Vis measurements revealed transmittance above 80% between 342 and 1000 nm. Impedance spectroscopy measurements, conducted between 50 and 425 °C, showed that at 300 °C the electrical conductivity varied from approximately 10−13 S/cm for CaNaBO-05 to 10−6 S/cm for CaNaBO-33, corresponding to a variation of about seven orders of magnitude. The DC conductivity was fitted according to Jonscher’s Power Law, and the apparent activation energy ( ), obtained from the Arrhenius model, decreased from 154 to 87.5 kJ/mol, suggesting that the substitution of Ca2+ by Na+ enhances ionic mobility, although showing a tendency toward non-linear compositional behavior at higher Na₂O contents. These results highlight the potential of the borate glass system for advanced studies of ionic conductivity and complex dielectric relaxation mechanisms. Editor: Universidade Federal da Grande Dourados Tipo: Tese

Produção de biochar a partir de resíduo agroindustrial da macaúba (Acrocomia aculeata), caracterização e avaliação de sua capacidade de adsorção na remoção de contaminantes

Fri, 12 Dec 2025 00:00:00 GMT

Título: Produção de biochar a partir de resíduo agroindustrial da macaúba (Acrocomia aculeata), caracterização e avaliação de sua capacidade de adsorção na remoção de contaminantes Autor(es): Maachar, Anderson Fialho Primeiro Orientador: Muzzi, Rozanna Marques Abstract: This work reports the production of biochar at different temperatures, using a simplified and low-cost procedure, aiming to obtain an adsorbent capable of removing pollutants in aqueous solutions; Methylene Blue (MB) and the Emerging Contaminant (EC) Bisphenol A (BPA) were tested. Biochars were produced from the carbonization of biomass at temperatures of 300 ºC (BC-300), 400 ºC (BC-400), 500 ºC (BC-500), 600 ºC (BC-600), 700 ºC (BC-700), and 800 ºC (BC-800), for 2 hours, in a standard electric muffle furnace, without purge and under limited oxygen conditions (non-inert atmosphere), with no pre-treatment, post-treatment or activation. The precursor used was Macaúba (Acrocomia aculeata) endocarp (EDP), a lignocellulosic material with physical and chemical characteristics favorable to carbonization, besides being accessible and low-cost. The changes in the physical and chemical properties of the precursor biomass and the differences between the biochars themselves were evidenced by TG/DTG, SEM, FT-IR, and XRD analysis and characterization techniques, thus confirming the influence of temperature on the biomass transformation. The results obtained for gravimetric yield (ηG) and the adsorption capacities of MB (qe-MB) and BPA (qe-BPA) were submitted to two-factor Analysis of Variance (ANOVA-2), followed by the Tukey test (p<0.05). The ηG produced under these conditions ranged from 11.05% to 35.98%, and there was a significant influence of the interaction between the evaluated factors (Carbonization Temperature x Atmosphere Condition), whose levels were 6 (six) temperatures between 300 ~ 800 ºC and 2 (two) conditions With Lid (CT) and Without Lid (ST); the CT method presented better yields at all tested temperatures. All biochars produced were able to remove MB and BPA, with better results for MB removal – for which qe-MB ranged from 5.37 to 35.13 mg.g-1 and qe-BPA from 0.92 to 23.17 mg.g-1; a significant interaction of the evaluated factors (Type of Adsorbent x Adsorbent Concentration) was observed; there were 7 (seven) levels for the types of adsorbents (EDP and the biochars) and 4 (four) levels for adsorbent concentrations (between 0.25 and 1.00 g.L-1) for the MB trials, while for BPA trials there were 5 (five) levels – between 0.50 and 5.00 g.L-1; for all tested adsorvates, BC-700 and BC-800 were superior to the others. Complementarily, BC-700 and BC-800 were submitted to textural characterization via N2 adsorption and exhibited maximum adsorbed quantity of 81.89 cm3.g-1 and 69,34 cm3.g-1, respectively; BC-700 was also superior in terms of specific BET surface area with 189.72 m2.g 1and BC-800 with 137.51 m2.g-1. The isotherms obtained for both materials exhibited shapes and hysteresis loops characteristic of mesoporous materials with a significant fraction of micropores. However, it was observed that with this low-cost and simplified carbonization method of Macaúba EDP, it is possible to produce, with yields equivalent to other methods, adsorbents capable of removing MB and BPA in aqueous solution; with those carbonized at the highest temperatures, 700 ºC and 800 ºC, being the most efficient, with BC-700 slightly better. Editor: Universidade Federal da Grande Dourados Tipo: Tese

Avaliação de parâmetros físicos-químicos e fitotoxicidade das águas do Córrego Paragem

Tue, 14 May 2019 00:00:00 GMT

Título: Avaliação de parâmetros físicos-químicos e fitotoxicidade das águas do Córrego Paragem Autor(es): Silva, Ediléia Amancio Primeiro Orientador: Vieira, Heberth Juliano Abstract: The stream Paragem is born south of the city of Dourados and crosses the urban and agricultural areas of the municipality. Its environment presents intense occupation, being subject to the most diverse environmental impacts. However, another complicating is the occupations and irregular ocuppancy that occur to a great extent of the stream. The present study had as objective to analyze the water quality at four points of the stream stops, with emphasis on physical-chemical analysis and phytotoxicity through germination and elongation Lactuca sativa. Four sampling points were selected, being two controls that are groundwater and osmosis water, in which water samples collected in April, May, and June of 2018. Water analysis consisted of pH, electrical conductivity, Redox Potential, turbidity, total solids, total dissolved solids, ammonia, as well as Principal Component Analysis and hierarchical analysis of the data. The phytotoxicity of the water samples was evaluated using the length of root and hypocotyl of the Lactuca sativa seedlings. Box tests followed by Tukey tests were used for the analysis of variance of root and hypocotyl lengths obtained at each sampling point. The sites studied Nascente, Palmeiras, Aguiar, and Frei Antônio were the electrical conductivity was above the limits of the current legislation in Brazil. The Frei Antônio presented the worst water quality with electrical conductivity and total dissolved solids higher than the current Brazilian legislation. It was concluded that physical-chemical analysis, together phytotoxicity of samples from stream water stopping using Lactuca sativa, was a valid indicator of environmental conditions and are useful tools to assess and compare the toxicity of stream surface water. Editor: Universidade Federal da Grande Dourados Tipo: Dissertação

Proposta de uma sequência didática para o ensino das propriedades físico-químicas da água fundamentada na pedagogia de Paulo Freire e nos três momentos pedagógicos

Fri, 31 Oct 2025 00:00:00 GMT

Título: Proposta de uma sequência didática para o ensino das propriedades físico-químicas da água fundamentada na pedagogia de Paulo Freire e nos três momentos pedagógicos Autor(es): Gonçalves, Luan Justino Primeiro Orientador: Martinez , André Luiz Abstract: Physics teaching in contemporary basic education is facing a profound crisis. The main challenges include overcrowded classrooms, a significant reduction in the number of hours devoted to the subject, the devaluation of the teaching profession in Brazilian basic education, inadequate working conditions, and the prevalence of a pedagogical culture centered on testing. Furthermore, the school curriculum presents itself as a list of content to be completed, predominantly addressed in a traditional way, with a focus on the teacher and based on the banking education model. In this context, it is essential to adopt alternatives that seek to minimize the educational gaps arising from these challenges. It is essential that teaching methods promote a problem-solving and liberating education, valuing the existential experiences of students in the teaching-learning process, with a view to fostering their awareness. Based on this premise, this teaching sequence was structured based on the dynamics of the Three Pedagogical Moments (3MP), proposed by Delizoicov, and developed from the perspective of Paulo Freire's pedagogy. The main objective was to promote students' awareness of the physical-chemical properties of water, as shown on the label of a mineral water. The proposal was organized into four meetings, each corresponding to two consecutive Physics classes, held in a state school located in the state of Mato Grosso do Sul, with a class of 3rd year high school students. In the first meeting, the contextualization of the generating theme, “physical-chemical properties of water”, was carried out using the label of a mineral water. Based on the raising of questions about the label, the teacher was able to explore the existential experiences of the students related to their understanding of the world. Then, the Three Pedagogical Moments were applied progressively: still in the first meeting, pH was addressed; in the second, the electrical conductivity of water; in the third, evaporation residues; and, in the bedroom, the temperature. During the implementation of the 3MP, the teaching sequence incorporated several teaching strategies, such as expository and dialogic classes, problem-solving experimentation, reading and interpretation of texts, conversation circle and virtual simulators. The analysis of the records produced by the students throughout the teaching sequence, the transcriptions of audios, the results of the bimonthly test and the students' evaluations regarding the conduct of the activities indicated possible evidence of awareness in relation to the content worked on. Editor: Universidade Federal da Grande Dourados Tipo: Dissertação