Síntese de nanopartículas de prata e deposição sobre TiO2 como estratégia de obtenção de fotocatalisadores para degradação de 17α-etinilestradiol em meio aquoso

Abstract

The improvement of processes for wastewater treatment is fundamental for the maintenance and progress of the health of living beings. With the emergence, over the last centuries, of new chemical compounds that present high complexity and stability, the accumulation of substances scientifically referenced as emergent compounds has been observed. This classification covers a number of substances such as drugs and hormones, and the great concern revolves around the removal of these substances from aquatic matrices, since many of these contaminants are already part of and are indispensable within today's society, such as synthetic contraceptive hormones, especially 17α-ethinylestradiol (EE2), being the main and most applied in the composition of contraceptive drugs. Under this context, conventional methods of water treatment are not very effective and efficient in the integral removal of these pollutants, and therefore, the application of advanced, technological and more effective techniques are increasingly necessary in this aspect. Studies related to Advanced Oxidative Processes (AOPs) for complementary application in wastewater treatment are growing and present positive results to contribute to this problem. Among the POAs, heterogeneous photocatalysis stands out for presenting low cost and potential for energy saving, with titanium dioxide (TiO2), in its commercial form P25, being the most applied in this field of study. Despite the increase in the number of studies and applications that TiO2 (mainly in the P25 form) demonstrates, some of its properties still have room for improvement in the aspect of photocatalytic efficiency, such as the time of recombination of electrons and especially the high band gap that this material presents. Therefore, the association, deposition, doping of TiO2 with other materials that can improve these deficiencies are promising, with silver (Ag) as one of the protagonists in this aspect. There are several methodologies for deposition of silver under the surface of the photocatalyst, being the impregnation method the simplest, low cost and that does not use aggressive organic solvents and / or exacerbated energy expenditure for its application in the formation of the material Ag / TiO2. That said, the impregnation method was used to synthesize photocatalysts with silver contents varying between 0% and 5% of the metal deposited under the P25 support. Through the interpretation of the characterizations, it was observed that the silver was deposited on the surface of TiO2 mostly in the form of oxides. When applying these materials in contact with the contaminant, it was observed that the material acted satisfactorily as an adsorbent for this hormone, and in 60 minutes it was possible to observe a considerable decrease in the absorption bands related to the presence of EE2. Finally, during the heterogeneous photocatalysis reaction, it was also possible to observe this same phenomenon for all materials, indicating that there was possibly photocatalytic degradation.