Cascas trituradas do jatobá-do-cerrado (Hymenaea stignocarpa) in natura e quimicamente tratado na adsorção de íons Níquel (II) e Cobre (II) em águas

Abstract

Toxic metals are usually removed from the effluent by chemical or physical processes, most of which are disadvantaged by the generation of toxic waste, high operating costs, and use of high added value reagents. Currently alternative methodologies involving the use of natural adsorbents have been evaluated, with promising results, for example the use of Jatobá-do-cerrado (Hymenaea stignocarpa), in natura (JIN) and Jatobá chemically treated (JQT). The fruit of the Jatobá-do-cerrado was collected in the city of Anápolis. After collection, the peels were separated from the pulp, dried and ground. The chemically treated jatoba was prepared by the addition of 0.3 mol L-1 HNO 3 and 0.75 mol L-1 NaOH. Subsequently the adsorbents were characterized in terms of their chemical and structural composition by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray analysis and Zero Load Point (pHpcz) (2 – 12). Then the effect of pH (2 – 9), mass of the adsorbent (10 – 250mg) was studied. The adsorption isotherms were linearized according to the mathematical models of Langmüir, Freundlich, Temkin and Dubini-Radushevich and non-linearized to Langmüir and Freundlich models. The thermodynamic parameters were determined at temperatures 303, 313, 323 K. Finally, the comparison was performed on a real sample. The pHpcz values were 5.4 and 6.4 for JIN and JQT, respectively. The optimum adsorption conditions of copper (II) and nickel (II) ions were: pH 5.5 and 6.0; adsorbent mass of 25, 150 and 250 mg. The experimental data adjusted to the Langmüir and Freundlich models suggesting the occurrence of adsorption in both monolayers and multilayers. In the temperature study the adsorption process was spontaneous only to the copper (II) and nickel (II) ions with JTT. The Gibbs energy values (ΔG °) suggested fisistion. The selectivity study showed that both at pH 5.5 and 6.0, adsorbents are more selective to copper (II) ions. The adsorption method applied in the real sample was efficient. In all studies, the adsorption used was better, indicating that the modified material has a higher removal capacity and can be used in the removal of copper (II) and nickel (II), considering its ease of use and viability environmental.