Preparação do carvão ativado a partir do carvão vegetal e sua avaliação no processo de adsorção do cobre presente em cachaça artesanal

Abstract

Cachaça is a typical Brazilian beverage, obtained by the distillation of the fermented of sugarcane juice, with an alcoholic strength of 38% to 48% v/v at 20°C. The cachaças homemade or “artesanais” are characterized in the majority by being produced in stills of copper, but the excess of this compound in the human body can be harmful to health. The national legislation establishes a maximum concentration of 5 mg/L of copper in cachaça, for the exportation this concentration should not exceed 2 mg/L. With the objective of reducing the concentration of copper in cachaça, the present work aims at the chemical activation of the charcoal from wood Eucalyptus urograndi, through the activating agent ZnCl2 and temperature of thermal treatment at 600°C, to be used as adsorbent in the removal of copper present in artisanal cachaça. For the activation procedure, the charcoal was crushed and separated in granulometries smaller than 0.15 mm, 0.15 to 0.500 mm and 0.50 to 1.00 mm in sieves. In the characterization of the activated charcoal (CVA) produced, one of the important aspects analyzed was the specific surface area, which was obtained a significant increase for all granulometries. An adsorption equilibrium study was realized for each granulometry of the CVA, to evaluate the percentage of copper removal in cachaça contaminated with 100 mg/L, varying the contact time between 15 and 240 minutes at the temperature of 20 and 60°C, in the proportion of 1:50 (grams of CVA: volume in mL of cachaça). The best copper removal result was 24.83% for CVA in granulometry from 0.50 to 1.00 mm in the time of 240 minutes at 20°C. Statistical planning showed that all factors analyzed, counting time, temperature and particle size have a significant effect on the copper removal response in the experimental range worked. Isotherm and adsorption kinetics graphs were prepared for the adsorption equilibrium capacity and saturation time, which presented results of 2.25 mg/g and 120 minutes, respectively. The Langmuir model was the one that best represents the experimental data in the isotherm, in kinetics the best model was the Elovich. In relation to adsorption thermodynamics, the parameters showed that the process is physical, spontaneous, exothermic and with a small degree of organization. The treatment of the contaminated cachaça with 10 mg/L of copper in the fixed bed was not satisfactory for the CVA produced, because it presented low capacity of copper removal and increase in the acidity content.