Batch adsorption of methylene blue dye using Enterolobium contortisiliquum as bioadsorbent: Experimental, mathematical modeling and simulation

Discoloration of cationic dyes in effluents is essential to reduce the impacts caused to the fluvial ecosystem. In this work, the adsorption of methylene blue was studied using Enterolobium contortisiliquum as bioadsorbent. The bioadsorbent showed structural and superficial potentiality in the process. The Langmuir model adjusted the experimental equilibrium data, presenting R-2 and R-adj(2) > 0.98 and EMR <3%. The adsorption kinetics of the process was evaluated by the diffusion models PVSDM, SDM and PVDM. The PVSDM and SDM models showed no difference in the adsorption kinetics of the dye in relation to the predicted values. The PVDM model was not representative of the experimental data of this work due to the physical structure of the bioadsorbent. The diffusion coefficient in the pore volume Dp was 3.8 x 10(-13) cm(2) s(-1). The Levenberg-Marquardt algorithm was used to optimize the objective function in the prediction of the Ds parameter. The Ds values for the PVSDM and SDM models, respectively, ranged from: 7.2 to 9.53 x 10(-6) cm(2) s(-1), 16.5 to 20.33 x 10(-6) cm(2) s(-1). The Ds values for the SDM model are higher than the PVSDM because it only considers the surface diffusion in intraparticle diffusion. The limiting step in both diffusion models is external mass convection because it has Biot <1.0. Once the balance was reached, the percentage of dye removal (R%) in the samples showed a value greater than 79%, showing the efficiency of the bioadsorbent in the process and enhancing its use for removing cationic dyes in the purification of contaminated effluents. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.