Estudo da biossorção do herbicida atrazina por meio da casca da semente de Moringa oleifera Lam.

Abstract

A wide range of organic and inorganic pollutants are found at considerable numbers in water resources, and sometimes they manifest some resistance to biological degradation and are not effectively removed by physico-chemical treatments, as in the case of the herbicide named Atrazine. The adsorption process has been considered as a good alternative for contaminants removal due to its low cost and easy operation. Thus, the objective of this work was to study the biosorption of Atrazine by shells of Moringa oleifera Lam. seeds in aqueous samples. The shells were chemically and thermally treated. Then, kinetics tests of 24 hours were performed using 0.3 g of the adsorbent previously prepared, in contact with 25 mL of 5 mg L-1 Atrazine solution. The pseudo-first and pseudo-second order models were fitted to the experimental data obtained. For the adsorption isotherms, it was considered the concentration of 2 to 15 mg L-1 and the temperature from 25 to 45 ºC. Freundlich and Langmuir models were fitted to experimental data. In addition, it was calculated the thermodynamics parameters: Gibbs free energy, enthalpy and entropy. In the kinetics study, the maximum removal observed was 98.4%, the equilibrium reached in 480 min and the best fitting model was the pseudo-second order model. In the isotherms study, it was observed that the process was favored by the increase of temperature. The values of thermodynamics parameters indicated that the biossorption occurred spontaneously, endothermic and reversible. According to the results, it was verified the high potential of Atrazine biosorption by Moringa oleifera Lam seed shells.