Abstract This study processed and characterized the biphasic ceramics Na2Ti3O7/Na2Ti6O13 that were obtained from semi-crystalline nanoparticles synthesized using sonochemical methods. Structural characterization techniques, such as X-ray diffraction and Raman spectroscopy, were used to identify the crystalline phases present. The Rietveld refinement revealed, among other structural parameters, the presence of two crystalline phases in compositions of 55.90% and 44.10% for sodium hexatitanate and trititanate, respectively. Via Raman spectroscopy, the presence of the main vibrational modes that correspond to the phases present in biphasic ceramics was confirmed. Finally, by using complex impedance spectroscopy, a decrease in the electrical resistance of both the grain (106 Ω-104 Ω) and its boundary (108 Ω -105 Ω) under increasing temperature was identified.

Resumo Nos últimos anos aumentou o interesse em lidar com o crescente problema ambiental proveniente da poluição de águas residuais oriundas das fábricas industriais. Visando minimizar esse impacto ambiental, a técnica de adsorção em meio aquoso tem sido uma alternativa bastante explorada na atualidade. Portanto, este trabalho teve como objetivo investigar a capacidade adsortiva de microcristais de trióxido de molibdênio (h-MoO3) usando o corante alaranjando de metila (AMe) como molécula em meio aquoso. Os microcristais foram obtidos por micro-ondas hidrotermal e estruturalmente caracterizados por diversas técnicas. O estudo cinético na adsorção do AMe resultou no melhor ajuste quando adotado o modelo de pseudossegunda ordem (R2=0,9997). O estudo da variação de temperatura indicou que a adsorção foi um processo favorável e espontâneo. Os valores obtidos tiveram boa concordância com o modelo de isoterma de Temkin, com capacidade máxima de adsorção de 656,9 mg.g-1 a 318 K.

Abstract In recent years, interest in dealing with the growing environmental problem arising from the pollution of wastewater from industrial factories has increased. In order to minimize this environmental impact, the aqueous adsorption technique has been an alternative widely explored today. Therefore, this study aimed to investigate the adsorptive capacity of molybdenum trioxide (h-MoO3) microcrystals using the methyl orange dye (MO) as a molecule in an aqueous medium. The microcrystals were obtained by hydrothermal microwave and structurally characterized by several techniques. The kinetic study on the adsorption of MO resulted in the best fit when adopting the pseudo-second order model (R2=0.9997). The study of temperature variation indicated that adsorption was a favorable and spontaneous process. The values obtained were in good agreement with the Temkin isotherm model, with a maximum adsorption capacity of 656.9 mg.g-1 at 318 K.