Coconut shell-based activated carbon as adsorbent for the removal of dye from aqueous solution: equilibrium, kinetics, and thermodynamic studies

Abstract

The need to develop more efficient adsorbent, comparable to commercially available adsorbent, is attracting significant interest as promising adsorbent for waste water treatment. In this study, the potential of activated carbon prepared from waste coconut shell (CSAC) for the removal of methylene blue (Mb) from aqueous solution was reported. Batch experiments were conducted to determine the adsorption isotherm and kinetics of Mb on CSAC. Langmuir, Freundlich and Temkin isotherm models were employed to fit and analyze the adsorption equilibrium data. The result shows Langmuir isotherm model gave the best fit and an adsorption capacity of 320.5 mg/g was obtained for Mb at pH value of 7, 0.02 g adsorbent dosage and contact time of 4.5 hour. The experimental kinetic data at different initial Mb concentrations was also analyzed with pseudo-first order, pseudo-second order and intraparticle diffusion models. The obtained results showed that the pseudo-second order model fits the adsorption kinetic data with R2 range of0.9985-0.9996. Finally, the thermodynamic parameters show that the adsorption of Mb on CSAC was spontaneous and endothermic in nature. This therefore suggests that (CSAC) is a viable adsorbent for effective removal of dye from wastewater effluent.
 Keywords: Activated carbon, Adsorption isotherms, Coconut shells, Methylene blue, kinetics.