Resumo O uso de pesticidas, como o fipronil, visa o aumento da produtividade, melhoria na qualidade dos produtos gerados e a diminuição de prejuízos. Contudo, os resíduos acumulados podem ser lavados durante as chuvas, ocasionando a contaminação de águas superficiais e subterrâneas. Nesse aspecto, a combinação entre semicondutores na forma de heteroestruturas é uma alternativa para degradação de tais poluentes. Heteroestruturas BiVO4/CePO4 e CePO4/BiVO4 foram sintetizadas pelo método de coprecipitação seguido de tratamento hidrotérmico assistido por micro-ondas, a 130 °C por 30 min. Os estudos de difração de raios X demonstraram a formação das heteroestruturas com estruturas de fase hexagonal (CePO4) e tetragonais scheelita e zircônia (BiVO4). Os resultados obtidos por microscopia eletrônica de transmissão e espectroscopia de infravermelho sugeriram a formação de uma região de interface, a qual contribuiu na sinergia entre os catalisadores. As heteroestruturas BiVO4/CePO4 e CePO4/BiVO4 apresentaram degradação de 80,06% e 99,50%, respectivamente, frente ao pesticida fipronil.

Abstract The use of pesticides, such as fipronil, aims to increase productivity, improve the quality of agricultural products generated, and reduce losses. However, pollutants accumulated can be loaded during rains, causing contamination in the surface and groundwater. Therefore, the combination of different semiconductors to form heterostructures can potentiate the degradation of such pollutants. BiVO4/CePO4 and CePO4/BiVO4 heterostructures were synthesized by co-precipitation method plus microwave-assisted hydrothermal treatment at 130 °C for 30 min. X-ray diffraction studies demonstrated the formation of heterostructures containing hexagonal phase (CePO4) and scheelite and zircon-type tetragonal phases (BiVO4). The obtained results by transmission electron microscopy and Fourier transform infrared spectroscopy results suggested the formation of an interface that contributed to the synergy between catalysts. BiVO4/CePO4 and CePO4/BiVO4 heterostructures showed degradation of 80.06% and 99.50%, respectively, of pesticide fipronil.

Biodiesel, known as a mixture of fatty acid ethyl/methyl esters, is seen as an alternative, ecofriendly, biodegradable and renewable non-fossil fuel. The use of heterogeneous catalysts for biodiesel synthesis can solve several problems associated with the homogeneous alkaline catalyzed-transesterification. Therefore, this work reports the evaluation of the commercial resin Amberlyst A26OH, a strong anion exchange resin, as a heterogeneous catalyst for the batch transesterification of refined palm olein with ethanol. It was studied the effects of the main operational parameters, considering the molar ratio of the reaction mixture (MRRM), namely the molar ratio of ethanol to olein taking into account only the ethanol added to the reaction system, and the total molar ratio (TMR), in this case considering also the amount of ethanol carried by the resin after its pretreatment. It was determined an optimal range of operational conditions by response surface methodology, guaranteeing conversion to ethyl esters higher than 96% with a catalyst amount corresponding to a range from 10.4 to 11.4% of the oil quantity, a temperature within the range of 55 to 60 ºC and a MRRM within the range from 3.5:1 to 6.0:1.

The modification of four extra virgin olive oils from different origins with refined soybean oil (SO), in the proportions of 0, 5, 10, 20 and 30% m/m, was studied using two approaches. First, the induction period (IP) was determined by Rancimat. In the second strategy, ion chromatography was used to quantify the formic and acetic acids, in their carboxylate forms (formate and acetate), present in the water contained in the measurement vessel of the Rancimat device, 21 h after the beginning of the induced oxidation of the samples. The content of the adulterant (SO) was linearly correlated with the IP (mean correlation coefficient (R) = 0.9858) and the concentration of the formate (mean R = 0.9979) and acetate (mean R = 0.9951). Also, it was observed that as the IP decreased and the formic acid and acetic acid concentrations increased, the monounsaturated fatty acids/polyunsaturated fatty acids ratio decreased.

Abstract Steady increase in prices of petroleum-based fuels and growing environmental concerns are boosting attention to alternative fuels. In this context, biodiesel has drawn attention as an alternative fuel, especially as a substitute to traditional diesel. Biodiesel is commonly produced from triacylglycerols and alcohol through transesterification reaction. Knowledge of equilibrium phase distribution of key components in transesterification systems is essential for a better understanding of the reaction pathway and for guiding the design and optimization of reactors and the products separation. This study reports experimental results and thermodynamic modeling of the liquid-liquid equilibrium of systems composed of soybean oil + monoacylglycerols + diacylglycerols + ethyl oleate + oleic acid + ethanol at 303.15 and 318.15 K. Experimental data were well correlated using NRTL, with a maximum deviation of 0.688%. As for UNIFAC, the deviations between predicted and experimental data ranged from 3.13 to 9.21%.

Através do método dos precursores poliméricos foram sintetizadas amostras de Ca0,98Sr0,01X0,01TiO3 (X= Eu3+, Sm3+ ou Pr3+), que submetidas a diferentes tratamentos térmicos foram obtidas com níveis de ordem-desordem estrutural distintos. Os materiais sintetizados foram caracterizados por difração de raios X, confirmando a obtenção de um material homogêneo com estrutura perovsquita do tipo ortorrômbica. Essa caracterização permitiu ainda calcular o tamanho médio de cristalito das amostras, que varia em função do íon terra-rara presente. Os resultados da emissão fotoluminescente confirmaram a presença desse fenômeno óptico à temperatura ambiente e sua relação com o nível de ordem-desordem estrutural do sistema. A emissão fotoluminescente mais intensa ocorre nas amostras tratadas termicamente a 500 °C (independente do íon dopante), a variação do dopante influencia na intensidade da emissão devido à transferência de carga entre a matriz hospedeira e o íon terra-rara emissor, onde a amostra dopada com íon Pr3+ apresenta transferência de carga mais eficiente e consequentemente maior intensidade na emissão fotoluminescente. Outro fator que favorece a propriedade óptica das amostras é a compensação de carga, pois contribui para o aumento da desordem estrutural devido à formação de vacâncias do íon Ca2+.

Through the polymeric precursor method were synthesized samples Ca0.98Sr0.01X0.01TiO3 (X= Eu3+, Sm3+ and Pr3+), which under different heat treatments were obtained with levels of distinct structural order-disorder. The synthesized materials were characterized by X-ray diffraction, confirming the obtaining of ahomogeneous material with perovskite-type orthorhombic structure. This characterization allowed evaluating the average crystallite size of the samples that varies depending on the rare-earth ion. The results of photoluminescence emission confirmed the presence of this optical phenomenon at room temperature and its relationship to the level of order-disorder structural system. The photoluminescence emission is more intense in samples annealed at 500 ° C (independent on the dopant ion), the variation of the dopant influence on the emission intensity due to charge transfer between the host and emitting rare-earth ion, where the doped with Pr3+ ion has charge transfer more efficient and hence more intense emission in the photoluminescence. Another factor that favors the optical property of the samples is the charge compensation, as it contributes to the increase in structural disorder due to formation of Ca2+ vacancies.

A esclerose múltipla (EM) é uma doença crônica e progressiva que se caracteriza por surtos de desmielinização que podem atingir qualquer topografia do cérebro, medula espinhal e nervo óptico. Sendo o diabetes insípido (DI) central causado, principalmente, em virtude de danos do sistema nervoso central (tais como trauma, cirurgia, tumor, infecção, sarcoidose), a EM está inclusa entre suas possíveis etiologias. Entretanto, a ocorrência dessa associação não é comumente descrita. A suspeita clínica deve ser feita na presença de poliúria e polidipsia ou hipernatremia refratária (em pacientes privados do acesso à água) durante a evolução da EM. Descreveremos um caso em que essa associação ocorreu e, após o início da terapêutica com desmopressina, a paciente reverteu o quadro clínico.

Multiple Sclerosis (ME) is a chronic progressive disease characterized by relapses of demyelination that can occur anywhere in the brain stem, spinal cord and optic nerve. Since central diabetes insipidus (DI) is mainly caused by central nervous system damage (such as trauma, surgery, tumor, infection, sarcoidosis), ME is included among its possible etiologies. However, this association is not commonly described. The clinical suspicion must be made in the presence of polyuria and polydipsia or refractory hypernatremia (in patients without free access to water) during the evolution of ME. We will describe a clinical report in which this association occurred and, after the beginning of desmopressin therapy, the clinical findings were reverted.