Síntese de nanotubos de carbono a partir de fontes alternativas para aplicação na adsorção de contaminantes emergentes

Abstract

This work has reported the synthesis of carbon nanomaterials (CNMs) by chemical vapor deposition method (CVD) at 800 °C using two alternative carbon sources, being these ethyl acetate and waste cooking oil. Moreover, it is reported the application of these materials for the adsorption of emerging contaminants, as the drugs paracetamol, ibuprofen, norfloxacin and amoxicillin, and the hormone 17α-ethinylestradiol. The results of transmission electron microscopy (TEM) showed that for both carbon sources used, the supported catalyst (Fe-Mo/MgO) employed was effective in the formation of nanostructures of the type multi-walled carbon nanotubes (MWCNTs) with morphologies known as bamboo-like and chain-like. The synthesis using waste cooking oil led to the production of more CNTs, presenting a higher yield, a fact which could be confirmed by scanning electron microscopy (SEM) images and by thermogravimetric analysis (TGA). TGA also showed that the CNTs synthesized from waste cooking oil have greater thermal stability structural organization, according to the ID/IG ratio obtained by Raman spectroscopy. Through X-ray photoelectron spectroscopy (XPS) it was observed that the materials synthesized using ethyl acetate presented an atomic percentage of oxygen slightly higher than those synthesized from waste cooking oil. The adsorption study of emerging contaminants demonstrated that the material synthesized from ethyl acetate presented greater adsorptive capacity, a fact which may be related to its larger surface area. Higher removal rates were obtained for the contaminants norfloxacin and 17α-ethinylestradiol, therefore, studies of kinetics and adsorption isotherms were carried out for both contaminants. Kinetic studies have pointed out pseudo-second order behavior, indicating that the speed of the adsorption process is affected by the availability of active sites in the adsorbent. Studies of adsorption isotherms pointed out different profiles, being this dependent on the contaminant. Finally, it was concluded that the use of these alternative carbon sources for the synthesis of CNTs by CVD in the condition applied on this work was feasible and that the synthesized materials had a good adsorptive capacity for the contaminants, norfloxacin and ethinylestradiol, compared to studies reported in the literature, ranging from 24.43 to 48.91 mg g-1.