Aproveitamento tecnológico da casca de amendoim em processo de biossorção de corante têxtil

Abstract

The textile industries have great potential for pollutants because they generate large quantities of effluents containing recalcitrant compounds, including dyes. Different processes have been employed in the decontamination of industrial effluents and studies indicate the adsorption using agroindustrial residues as adsorbent matrices as promising processes in the removal of color. In this context, the present work had the objective of evaluating peanut shell biomass as an alternative adsorbent in the process of dye removal (Reactive Blue 203) in synthetic and industrial effluent. For this, characterization analyzes of the adsorbent material were performed, revealing a high amount of fibers (69,25%), among them polysaccharides (glucan and xylan) and lignin (39,4%). The biomass showed a pHzcp of 6,9, the scanning electron microscopy demonstrated that its surface is highly porous and the BET specific surface analysis indicated a surface area of 0,4431 mg.g-1 and mean pore diameter of 20,120 Å in ground biomass with a particle size of 0,250 mm. A 23 central composite rotational design was use to evaluate and define the best process conditions, studing the influence of the parameters pH, solution temperature and adsorbent granulometry on the color removal capacity of synthetic effluent (Reactive Blue 203). The pH and temperature variables showed a significant influence on the color removal process and, as the best process conditions, pH of 3,0, temperature of 30oC and particle size of 0,250 mm were define. The equilibration time was reach after 400 minutes of contact. The kinetic model of pseudo-second order was the one which best described the adsorption process. The adsorption isotherms were evaluate from the mathematical models of Langmuir and Freundlich, and the Langmuir model best described the process. The thermodynamic parameters shown that Gibbs free energy presents positive values, indicating that the process is not spontaneous. Negative enthalpy values suggest an exothermic nature of the adsorption and negative entropy values indicate an increase in the degree of organization of the system. The activation energy of the dye adsorption process on the studied matrix indicates an activated chemical adsorption. The peanut hulls showed potential for color removal in industrial effluent (66,83%), which can be improved by employing more specific process conditions. On the other hand, the reutilization of the material was not optimal under the desorption conditions because the chemical nature of adsorption.