Adsorção dos íons metálicos Cu2+ e Mn2+ em sistema bicomponente utilizando carvão ativado preparado a partir de sabugo de milho como adsorvente

Abstract

Heavy metals are used in several areas, especially in the pulp and paper industry, since their effluents contain high levels of copper and manganese, which can cause harmful effects on living systems due to their toxic nature, non-biodegradable and accumulate in organisms. This problem has led several research groups to seek treatment alternatives. Adsorption using activated carbon prepared from agro-industrial residues has been presented as an alternative for the treatment of effluents containing heavy metals. In view of the above, this work proposes the use of activated carbon prepared from corn cob as an adsorbent for the removal of Cu2+ and Mn2+ metallic ions in mono and bicomponent systems. Corn cob activated carbon was chemically activated with H3PO4. The characterization of corn cob and activated carbon was carried out by Fourier transform infrared spectroscopy, Boehm titration and determination of the pH of the zero charge point. The influence of the initial pH of the solution on the adsorptive process was studied in order to determine the pH used in further studies. Based on the results obtained, kinetic and adsorption equilibrium studies were carried out for the mono and bicomponent systems. The characterization indicated that the activation promoted an increase of carboxylic groups on the surface of the adsorbent, reduction of the pHZCP value from 4.7 in the corn cob to 3.0 in the activated carbon, increasing the pH range of the solution in which the surface of the coal becomes negatively charged, which favored the adsorption of Cu2+ and Mn2+ ions. In the study of the effect of the initial pH of the solution in a single-component system, pH 4 and 6 showed better results for Cu2+ and Mn2+ ions, respectively, whereas in the bicomponent system it was pH 4. The model that best represented the experimental data of the kinetic evolution was the pseudo-second order for monocomponent systems and for Cu2+ in the bicomponent system, while for Mn2+ it was the pseudo-first order model. In the adsorption equilibrium, it was found that the model that best fitted the experimental data was Sips for Cu2+ and Langmuir for Mn2+ in a monocomponent system. The experimental adsorptive capacity was 0.39 mmol•g-1 for Cu2+ and 0.22 mmol•g-1 for Mn2+. Regarding the bicomponent system, the antagonistic effect of the presence of Cu2+ for the adsorption of Mn2+ was verified, and the model that best described the process was the extended Langmuir process, as it indicated the highest affinity of Cu2+ with activated carbon. The results of this work demonstrate the technical potential of activated carbon prepared from corn cob for the adsorption of Cu2+ and Mn2+ ions in mono and bicomponent systems.