Síntesis de aerogeles 3D de óxido de grafeno reducido con gradiente de porosidad para remoción de aceites vegetales de aguas artificiales.

Abstract

Reduced graphene oxide (rGO) aerogels have been studied for contaminants removal from water sources, namely vegetable oils, in aqueous solutions. These materials exhibit excellent properties such as low density, high porosity, and specific surface area, making them an excellent alternative for absorption applications. In this research, the pore gradient in the obtained aerogels was studied using hydrothermal reduction, followed by a freeze casting process to form the matrix and the addition of a spacer, in this case, carbon nanotubes (CNT) and ethylenediamine (EDA), to finally obtain the aerogel through a lyophilization process. The samples were characterized using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). Absorption tests were performed with vegetable oils of different dynamic viscosities. The results showed that the porosity of the aerogels monoliths obtained, which were divided in three sections (Top, middle and bottom) decreased from the upper section to the lower section. Furthermore, the aerogels performed better as the dynamic viscosity of the oil and the pore gradient increased, especially from the lower section to the upper section. The unmodified aerogels achieved the best absorption capacity of 66.44 g/g in its top section. On the other hand, the oil absorption performance was better for the freeze-molded aerogels at a lower rate (higher temperature) compared to a higher rate. Regarding the spacers, it was observed that modification with CNT resulted in lower absorption performance of the aerogels due to the dispersing agent content. Modification with EDA showed the best absorption performance regardless of the pore gradient, reaching a maximum value of 122 g/g at room temperature. Finally, absorption tests were conducted at 60 °C, and it was determined that all EDA-modified aerogels improved their performance in terms of absorption capacity (a maximum of 156 g/g was recorded) and absorption rate (a maximum of 15 g/(g*s) in just 10 s.