Evaluation of Ocotea puberula bark powder (OPBP) as an effective adsorbent to uptake crystal violet from colored effluents: alternative kinetic approaches.

Abstract

The Ocotea puberula bark powder (OPBP) was evaluated as an effective adsorbent for the removal of crystal violet (CV) from colored effluents. OPBP was characterized and presented a surface with large cavities, organized as a honeycomb. The main functional groups of OPBP were O-H, N-H, C=O, and C-O-C. The adsorption of CV on OPBP was favorable at pH9 with a dosage of 0.75gL-1. The Avrami model was the most suitable to represent the adsorption kinetic profile, being the estimated equilibrium concentration value of 3.37mgL-1 for an initial concentration of 50mgL-1 (CV removal of 93.3%). The equilibrium was reached within 90min. The data were better described by the Langmuir isotherm, reaching a maximum adsorption capacity of 444.34mgg-1 at 328K. The Gibbs free energy ranged from - 26.3554 to - 27.8055kJmol-1, and the enthalpy variation was - 11.1519kJmol-1. The external mass transfer was the rate-limiting step, with Biot numbers ranging from 0.0011 to 0.25. Lastly, OPBP application for the treatment of two different simulated effluents was effective, achieving a removal percentage of 90%.