Utilização da casca do maracujá amarelo como biossorvente para a remoção de atrazina de soluções aquosas

Abstract

The need to improve efficiency in agricultural production has increased the use of agrochemicals, but these inputs have a great polluting potential to the environment and to humans. Atrazine has been widely used in several countries and has gained prominence due to its presence in surface and groundwater. The reported processes involving the biosorption of atrazine involve chemically or thermally modified biosorbent materials. In this sense, the present study proposes the use of the biosorbent of the yellow passion fruit peel Passiflora edulis f. flavicarpa, in order to make the adsorption process, less impactful to the environment, economically viable and with fewer steps. To evaluate the adsorption capacity of the yellow passion fruit peel, initially, characterizations (pHpcz, BET, SEM, ATG, FTIR) of this biosorbent were performed. The yellow passion fruit peel presented a specific area of 2.00 m2 g-1 and null micropores, besides a low pore distribution, as determined by BET analysis. The material presented heterogeneous morphology identified by scanning electron microscopy (SEM). The pHpcz was evaluated in a batch system submitted to 100 rpm agitation for 24 hours, varying the pH parameter, and its zero-loading point was determined at pH 5.90±0.20. The thermogravimetric analysis determined the presence of hemicellulose, lignin, cellulose, pectin and water, according to the thermogravimetric profile obtained, a fact corroborated by the FTIR analysis. The evaluation of the influence of the adsorbent mass was performed by varying the mass between 10.0 to 100.0±0.2 mg of adsorbent, showing an adsorption capacity of 1.82 mg g-1 for 30.0±0.2 mg of adsorbent. The maximum adsorption capacity increased when evaluating the influence of pH. At pH 4.00±0.20 the adsorption capacity was 2.24 mg g-1 using 30.0±0.2 mg. The adsorption kinetics using 30.0±0.2 mg of adsorbent at pH 4, showed an equilibrium time of 1440 minutes and the model that best fitted the experimental data was the Elovich model. For the adsorption isotherms, the Freundlich model was the best fit to the experimental data at the three temperatures studied. In addition, this study showed that the concentration had an influence on the adsorption process, indicating that a higher concentration favors the multilayer adsorption effect. The maximum adsorption capacity evaluating temperature and concentration was 50.26 mg g-1, which represents approximately 75% removal of atrazine in aqueous solution with concentration of 100 mg L-1, achieved in an equilibrium time of 1440 minutes, pH 4.00±0.20 and 30.0±0.2 mg of adsorbent. The thermodynamic parameters indicated a physisorption process, based on hydrogen bonds, π-π and multilayer interactions, which were corroborated by FTIR analysis after adsorption. Therefore, the results obtained suggest that the yellow passion fruit peel has a high potential to be used in atrazine adsorption process.