Estudo da adsorção de compostos tiofênicos utilizando carvão de casca de coco de dendê submetido a modificações físico-químicas

Abstract

The aim of this work was to characterize and to evaluate the performance of different modifications in activated carbon derived from coconut shell (AC) by heat treatment (ACT), oxidative treatment (ACO), aluminum impregnation by incipient wetness method before (ACIN-Al) and after oxidative treatment (ACO-Al). All the adsorbents were characterized by morphologic, textural and physicochemical analyses. The adsorption experiments were carried out in closed and batch system to obtain kinetic and equilibrium data to benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) compounds. The Langmuir isotherm was used to describe equilibrium data. Phenomenological models were used to describe kinetic data. The adsorbents characterization showed that are heterogeneous materials, with high surface area and micropore predominance. The oxygenated functional groups were identified on the adsorbent surface as well as AlO(OH) and Al2O3 on the ACIN-Al and ACO-Al adsorbents. The mathematical modeling of adsorption experiments showed that the ACO-Al adsorbent presented the best performance on DBT removal with qmax= 0.73 mmol g-1 and the internal diffusion model described well the kinetic data. The adsorption maximum capacities of BT and 4,6-DMDBT compounds were 0.24 and 0.36 mg g-1, respectively. The adsorption capacity followed the sequence DBT>4,6-DMDBT>BT, what indicates that methyl groups intensify the steric effect and decrease interactions in the sulfur atom. These results showed that the adsorption of thiophenic compounds occurs mainly by interactions of π electrons between the aromatic rings of the molecules and the adsorbent’s surface, as well as by weaker interactions as S-M.