Equilibrium, kinetic and thermodynamic of direct blue 86 dye adsorption on activated carbon obtained from manioc husk

Abstract

Objective. To establish by means of experimenting by batch the capacity of removal, the kinetics and adsorption thermodynamics of activated carbon prepared from manioc husk (Manihot esculenta) in the removal of direct blue 86 dye. Materials and methods. Firstly, the experimental methodology worked on the preparation of activated carbon by chemical activation of manioc husk with H3PO4 calcined at 530°C. In the characterization the texture properties were determined by means of the blue methylene and iodine indices, the basic and acidic functional groups were quantified by the Boehm method, and the proximate analyses were done following the norms ASTM D2867-70, ASTM D2866 and ASTM D2866-94. During the batch studies, the effect of several parameters over the adsorption capacity was evaluated: pH (2, 4, 8 and 10), temperature (25, 30 and 40°C) and initial concentration of the dye (20, 40, 60, 80 and 100 mg/L). Both physicochemical and adsorption characteristics of the activated carbon from manioc husk (CAY) were compared against those of a commercial brand (CAM). Results. The results of characterization showed that both carbons have a chemistry heterogeneous surface, acidic for CAY and basic for CAM. The maximum capacity obtained was 6.1 mg/g for CAY and 3.7 mg/g for CAM. The thermodynamic calculations showed that the removal was spontaneous. The kinetics for both carbon samples fits a pseudo second-order model. Conclusions. The activated carbon obtained from the manioc husk can be considered an efficient adsorbent for the removal of dyes.