Avaliação da eficiência do endocarpo do fruto de tucumã (Astrocaryum aculeatum) na remoção do íon níquel (ii) em meio aquoso.

Abstract

The increase in pollution due to the incorrect disposal of waste containing heavy metals, both by industries and by urban waste, has aroused a great concern with the chemical contamination of rivers and soils, since these metals are toxic and dangerous human health and also other living organisms. In addition, another problem is the low concentrations, close to 2 mg/L, which are found and the resistance they offer to the usual methods of effluent treatment. Therefore, it becomes necessary to search for alternative and lower cost methods in the treatment of effluents. Among these methods, we can mention biosorption, which is a cheaper method that uses residual biomass. Therefore, the objective of this work was to verify if the endocarp of Astrocaryum aculeatum fruit can be used as a biosorbent material in the removal of nickel (II) ion in aqueous medium. For this, an experimental planning was made, aiming to determine the best conditions for the adsorption process. Tests for the adsorption isotherms were also carried out, fitting the experimental data to the Langmuir and Freundlich models to assess whether the removal of nickel (II) by the endocarp of the Astrocaryum aculeatum fruit is favorable. Obtaining the biosorbent material was started by drying in an oven at 55 °C for 3 days, followed by drying the endocarp at 55 °C for another day, then they were crushed in a knife mill and particle size analysis was performed using sieves of different openings, ranging from 2 to 0.125 mm. For the experimental design tests, the variables nickel (II) concentration and amount of biosorbent were studied, ranging from 50 to 150 mg/L of nickel (II) and biosorbent load from 0.25 to 0.75 g, the samples were mechanically shaken for 4 hours and centrifuged for 20 minutes at 4000 rpm, the tests were carried out at a temperature of 25 °C. The process conditions for the adsorption isotherm tests were: 0.50 g biosorbent load; temperature 25°C; stirring time of 4 hours with mechanical stirring of 200 rpm. At the end of the adsorption assay, the samples were centrifuged at 4000 rpm for 20 minutes. The method used to quantify nickel (II) in aqueous solution was cyclic voltammetry in the potentiostat device. The effectiveness of using tucumã fruit endocarp for nickel (II) adsorption was proven. The adsorption capacities obtained from the Langmuir and Freundlich models were 714.29 mg.g-1 and 0.0116 L.mg-1, respectively, where the biosorption tests were better fitted to the Freundlich model.