Produção de carvões ativados preparados a partir de diferentes materiais precursores

Abstract

This study had as an objective to produce activated carbon (ACs) from Bambusa vulgaris, Eucalyptus dunnii and endocarp of Cocos nucifera; characterize the materials produced and evaluate their potential for adsorption of the methylene blue compound, contaminant of the textile industry. For this, activated carbon was produced via physical, using the water vapor as the activating agent. BET surface area (SBET), scanning electron microscopy (SEM), Boehm titration method (BOEHM), point of zero charge (pHpzc) and thermogravimetric analysis (TGA) were characterized. In order to evaluate these materials application, adsorption studies were performed with a contaminant from the textile industry, the methylene blue dye which was considered as a model compound for several adsorption studies. The precursors studied have produced excellent ACs which can be used as adsorbents in aqueous media. The ACs produced from bamboo and eucalyptus obtained superior performance to that produced from the coconut endocarp, which was used as a quality comparative in this study. All the ACs showed very close characteristics, but the activated carbon of bamboo and eucalyptus had better performance with a SBET superior than 500 m2 g-1, removal percentage above 90% at equilibrium time and maximum adsorption capacity around of 300 mg g-1. The three ACs produced obtained pHpzc from 7.0 to 7.5, presented predominance of acidic groups on their surface, mainly the carboxylic groups, and the analysis of the obtained micrographs showed a porosity development due to the activation. The materials have shown good thermal stability, and the regeneration process is possible with small mass losses. Although the bamboo AC has SBET superior to the eucalyptus AC, this did not guarantee that it obtained better performance in adsorption kinetics for the methylene blue, which confirms that other factors such as pore size influence the adsorption process. The bamboo and eucalyptus ACs fit better to the Langmuir model (monolayer), while the coconut AC to the Freundlich (multilayer) model. Finally, it is concluded that the different precursors studied allowed the activated carbons production with excellent textural and adsorptive characteristics; and further studies should be conducted to improve even more the qualities.