Potential of Cedrella fissilis bark as an adsorbent for the removal of red 97 dye from aqueous effluents

Abstract

Cedar bark (Cedrella fissilis), a waste from wood processing, was evaluated as an adsorbent for the removal of red 97 dye from effluents. The material exhibited an amorphous structure, irregular surface, and was mainly composed of lignin and holocellulose. The adsorption was favored at pH 2.0. The general order model was most suitable for describing the experimental kinetic data, being the equilibrium reached in around 30 min. The isotherm experiments were better described by the Langmuir model. The maximum adsorption capacity was 422.87 mg g^-1 at 328 K. The values of standard Gibbs free energy change (ΔG⁰) were from - 21 to - 26 kJ mol^-1, indicating a spontaneous and favorable process. The enthalpy change (ΔH⁰) was 18.98 kJ mol^-1, indicating an endothermic process. From the fixed bed adsorption experiment, an inclined breakthrough curve was found, with a mass transfer zone of 5.36 cm and a breakthrough time of 329 min. Cedar bark was able to treat a simulated effluent attaining color removal of 86.6%. These findings indicated that cedar bark has the potential to be applied as a low-cost adsorbent for the treatment of colored effluents in batch and continuous adsorption systems.

Keywords: Adsorption; Cedar bark; Fixed bed; Red 97; Simulated effluent.