Elucidação do mecanismo de adsorção de amoxicilina em sílica mesoporosa modificada Al-MCM-41
Data
2024-07-06
Autores
Macedo, Vinícius Matheus Silva 
Orientadores
Felisbino, Romilda Fernández
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Atualmente sabe-se que dois terços dos rios do mundo inteiro estão poluídos por contaminantes emergentes, como os antibióticos, agrotóxicos, pesticidas, hormônios e analgésicos. Os métodos convencionais por parte das ETE’s e/ou ETA’s ainda não realizam a remoção destes contaminantes dos corpos d’água, uma parcela significativa retorna para a rede hídrica e é novamente consumido pela população, o que possibilita o surgimento de microrganismos altamente resistentes aos antibióticos, como as superbactérias (ARBs). Um dos métodos que pode ser empregado na remoção desses contaminantes, como os antibióticos, é o processo de adsorção. Nesse caso, um dos fatores que tem forte influência no fenômeno de adsorção é a propriedade dos adsorventes, que geralmente são sólidos porosos. Nesse sentido, as sílicas mesoporosas apresentam um forte potencial de aplicação devido à alta área específica, no entanto há poucos relatos na literatura sobre o uso dessas sílicas como adsorventes na remoção desses resíduos. Este trabalho tem como objetivo estudar e elucidar o mecanismo de adsorção de amoxicilina (AMX) em sílica mesoporosa modificada Al MCM-41 (Si/Al de 10,5). As sílicas foram sintetizadas via rota hidrotérmica e caracterizadas por DRX, fisissorção de N2, FTIR, MEV/MET e TG/DTG. Os resultados mostram que a substituição isomórfica do Si por Al gera uma deformação na estrutura da rede da sílica gerando sólido com menor ordenamento da fase hexagonal (área específica de 737 m2 g-1). Os estudos cinéticos de adsorção mostram que a AMX apresenta uma afinidade moderada pela superfície da Al-MCM-41 e que atinge o tempo de equilíbrio após 24h de contato. O modelo cinético de pseudo primeira ordem é o que melhor se ajusta a esse sistema indicando que provavelmente estejam ocorrendo interações não somente eletrostáticas, mas também químicas entre a AMX e a superfície da Al-MCM-41. Os resultados de equilíbrio de adsorção indicam que o modelo de Freundlich é o que melhor se ajusta aos dados experimentais do sistema AMX-Al-MCM-41, sugerindo uma heterogeneidade na distribuição de energia dos sítios adsortivos. Através dos espectros SERS do sistema e dos mapas de potencial eletrostático propôs-se que uma das possíveis interações entre a AMX e a superfície da Al MCM-41 se dá via interações eletrostáticas entre o grupo amino protonado da AMX com grupos carregados negativamente na superfície da sílica, com a possibilidade de ocorrência de troca iônica entre a AMX e os cátions Na+ compensadores de carga na estrutura.
It is currently known that two-thirds of the world's rivers are polluted by emerging contaminants, such as antibiotics, pesticides, hormones and analgesics. Conventional methods used by STS's and/or WTS's still do not remove these contaminants from water bodies. As a significant portion returns to the water distribution system and is again consumed by the population, which allows the emergence of microorganisms that are highly resistant to antibiotics, such as superbacterias (ARBs). One of the methods that can be used to remove these contaminants, such as antibiotics, is the adsorption process. In this case, one of the factors that has a strong influence on the adsorption phenomenon is the property of the adsorbents, which are generally porous solids. In this sense, mesoporous silicas have a strong application potential due to their high specific area, however there are few reports in the literature on the use of these silicas as adsorbents in the removal of these residues. Therefore, the present work aims to study and elucidate the adsorption mechanism of amoxicillin (AMX) on modified mesoporous silica Al-MCM-41 (Si/Al of 10.5). The silicas were synthesized via the hydrothermal route and characterized by XRD, N2 physisorption, FTIR, SEM/MET and TG/DTG. The results show that the isomorphic replacement of Si by Al causes a deformation in the structure of the silica network, resulting a solid with a lower ordering of the hexagonal phase (specific area 737 m2 g-1). Adsorption kinetic studies show that AMX has a moderate affinity for the Al-MCM-41 surface and reaches equilibrium time after 24h of contact. The pseudo first order kinetic model is the one that best fits this system, indicating that not only electrostatic but also chemical interactions probably occur between AMX and the Al-MCM- 41 surface. The adsorption equilibrium results indicate that the Freundlich model best fits the experimental data of the AMX-Al-MCM-41 system, suggesting a heterogeneity in the energy distribution of the adsorption sites. Through SERS spectra of the system and electrostatic potential maps, it was proposed that one of the possible interactions between AMX and the surface of the Al-MCM-41 occurs via electrostatic interactions between the protonated amino group of AMX with characteristic charged groups on the silica surface, with the possibility of ion exchange occurring between AMX and the charge compensating Na+ cations in the structure.
It is currently known that two-thirds of the world's rivers are polluted by emerging contaminants, such as antibiotics, pesticides, hormones and analgesics. Conventional methods used by STS's and/or WTS's still do not remove these contaminants from water bodies. As a significant portion returns to the water distribution system and is again consumed by the population, which allows the emergence of microorganisms that are highly resistant to antibiotics, such as superbacterias (ARBs). One of the methods that can be used to remove these contaminants, such as antibiotics, is the adsorption process. In this case, one of the factors that has a strong influence on the adsorption phenomenon is the property of the adsorbents, which are generally porous solids. In this sense, mesoporous silicas have a strong application potential due to their high specific area, however there are few reports in the literature on the use of these silicas as adsorbents in the removal of these residues. Therefore, the present work aims to study and elucidate the adsorption mechanism of amoxicillin (AMX) on modified mesoporous silica Al-MCM-41 (Si/Al of 10.5). The silicas were synthesized via the hydrothermal route and characterized by XRD, N2 physisorption, FTIR, SEM/MET and TG/DTG. The results show that the isomorphic replacement of Si by Al causes a deformation in the structure of the silica network, resulting a solid with a lower ordering of the hexagonal phase (specific area 737 m2 g-1). Adsorption kinetic studies show that AMX has a moderate affinity for the Al-MCM-41 surface and reaches equilibrium time after 24h of contact. The pseudo first order kinetic model is the one that best fits this system, indicating that not only electrostatic but also chemical interactions probably occur between AMX and the Al-MCM- 41 surface. The adsorption equilibrium results indicate that the Freundlich model best fits the experimental data of the AMX-Al-MCM-41 system, suggesting a heterogeneity in the energy distribution of the adsorption sites. Through SERS spectra of the system and electrostatic potential maps, it was proposed that one of the possible interactions between AMX and the surface of the Al-MCM-41 occurs via electrostatic interactions between the protonated amino group of AMX with characteristic charged groups on the silica surface, with the possibility of ion exchange occurring between AMX and the charge compensating Na+ cations in the structure.