CT - DEMAT - Artigos publicados em periódicos

URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/174

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Influence of solution pH on forming silver molybdates obtained by sonochemical method and its application for methylene blue degradation
(Elsevier, 2019-06-15) Ferreira, Erik Alexander Cunha; Andrade Neto, Nivaldo Freire de; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Catalytic processes such as heterogenous photocatalysis or adsorptions have been extensively studied due to the difficulty in treating organic effluents, mainly textiles. The catalysts stability is essential to enable their ap- plicability, so that the catalytic converter does not turn into secondary residues after the catalytic cycle, enabling its re-employment in the catalytic process. In this work was studied the photocatalytic activity of different phases of silver molybdates obtained by the sonochemical method at different pH in the medium reaction. The powders were characterized by X-ray diffraction (XRD) field emission scanning electron microscopy (FE-SEM), and diffuse reflectance spectroscopy was used to estimate the Egap of the powders. The photocatalytic activity of the powders was measured by varying the degradation of the methylene blue dye (MB). According to the XRD patterns, the crystalline structure of the obtained silver molybdates changes from Ag2Mo3O10. 2H2O at very acidic pH 1 and 2, to pure Ag2Mo2O7 with the values of pH 3 and 4 it is then converted into Ag2Mo2O7 and Ag2MoO4 phases in pH 5, and shifts to pure Ag2MoO4 phase when the pH is increased up to 6. The results indicate that the microstructures of Ag2Mo3O10. 2H2O and Ag2Mo2O7 phases have high adsorbent properties, with the powders obtained at pH 1 and 2 being able to completely remove the MB from the solution in 5 min and the powders of Ag2Mo2O7 phases removing up to 90% of MB after 5 min of exposure without UV irradiation. In contrast, the powders with Ag2MoO4 phase showed high photocatalytic properties, being able to removing up to 90% of MB in less than 20 min and 40 min of ultraviolet exposure to powders obtained at pH 5 and 6, respectively. All presented catalysts maintained their stability and performance after 3 test cycles
Sulfur removal from model fuel by Zn impregnated retorted shale and with assistance of design of experiments
(Springer, 2018-03-05) Martinelli, Antonio Eduardo; Lima, Flávia Melo de; Borges, Talitha de Andrade; Braga, Renata Martins; Melo, Dulce Maria de Araújo
There is global concern about acid rain and other pollution which is caused by the consumption of oil. By decreasing sulfur content in the oil, we can reduce unwanted emissions and acid rain. Shale was used which is a solid waste generated in the pyrolysis of shale, impregnated with Zn as an adsorbent which removes sulfur present in fuels from the hexane/toluene model solution. An influence of the agitation time (60–180 min), temperature (25–35 °C), adsorbent mass (0.1–0.25 g), and initial sulfur concentration (100–250 ppm) factorial 24 with three central points totaling 19 experiments was applied to investigate the effect of the variables on the efficiency of sulfur removal in fuels. The values of the parameters tested for maximum sulfur removal were obtained as follows: contact time = 180 min, temperature = 35 °C, adsorbent mass = 0.25 g, and initial sulfur concentration = 100 ppm. The mathematical model proposed with R2 99.97% satisfied the experimental data. This may provide a theoretical basis for new research and alternative uses for tailings of schist industrialization in order to evaluate its potential

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