Low-cost activated carbon from the husk of Pará nuts for dye removal from aqueous solution: kinetic and thermodynamic mechanism study

Abstract

The use of activated carbon produced from the husk of Pará nuts, Bertholletia excelsa, as an ecological and low-cost alternative for the adsorption of reactive orange 16 dye (RO-16) was used. The adsorbent material, CA-700³²⁵, was synthesized by carbonizing the biomass of Brazil nuts at 700 ºC for 2h in order to obtain activated carbon with high adsorptive capacity. The superficial characterization was performed by FTIR and BET. Langmuir, Freundlich and Temkin isotherms were used to describe the adsorption equilibrium, while the adsorption kinetics was studied using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. The removal of RO-16 depends on the pH of the medium, reaching a maximum index at pH 1.0. At a dosage of 5.0 g/L, the removal of RO-16 was greater than 99%. Adsorption isotherms had a better fit of the experimental data with Langmuir model, revealing that the adsorption of RO-16 in the CA-700³²⁵ occurs in a monolayer, with a maximum capacity of adsorption in a monolayer of 154.8 mg/g, the adsorption equilibrium appears in 150 min and that the adsorption kinetics follows the pseudo-second order model. The present study reports that the low-cost material is very promising for the treatment of the textile industry effluents.