Adsorção de cromo (III) por resíduos de laranja in natura e quimicamente modificados

Abstract

The waste containing heavy metals originating from mining and industrial activities, can cause damage to the environment and human health. Although chromium is considered an essential metal, when found in high concentrations can be harmful. Therefore, the aim of this study was to investigate the efficiency of chemical treatments in husk, bagasse and bark with orange pulp, in order to treat wastewater aqueous contaminated by chromium (III). The modification refers to a treatment sodium hydroxide and citric acid, which aims at introducing carboxylate groups. Tests were conducted in batch systems containing chromium, and the concentrations were determined using the atomic absorption spectrophotometer flame. We analyzed the adsorption as a function of pH, contact time, metal concentration, the desorption capacity and thermodynamic parameters. The changes were observed in the infrared by the appearance of a peak at 1730cm^-1, which refers to carboxylate groups. The time required to reach the adsorption system balance was approximately 500 minutes and the kinetics follows a behavior described by the equation of pseudo-second order. Was evaluated in relation to the adsorption models of Langmuir and Freundlich, being the model of Freundlich the best applied to the process. Besides increasing the adsorbent properties, the system became more spontaneous after the chemical treatment, verified by the low values of Gibbs energy.