Utilization of Cocoa Pod Husk for the Removal of Remazol Black B Reactive Dye from Aqueous Solutions: Kinetic, Equilibrium and Thermodynamic Studies

Abstract

This study aims at investigating the adsorption of Remazol Black B reactive (RBBR) dye on cocoa pod husk based activated carbon (CPHAC) in batch process. The effects of initial dye concentration, contact time, temperature and pH were evaluated. At the lowest initial dye concentration (20 mg L -1), the highest percentage RBBR dye removal by CPHAC was achieved (76.3%). Equilibrium was reached at 300 and 350 min, respectively. The equilibrium data were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. It was found that Langmuir model fitted the adsorption most with maximum adsorption monolayer coverage of 22.12 mg g-l Two kinetic models were used to fit the kinetic data; pseudo-first-order and pseudo-second-order models. The pseudo second-order model provided the best correlation for the adsorption of RBBR dye on CPHAC. Thermodynamic parameters such as change in Gibb's free energy ~Go, change in enthalpy ~Ho and change in entropy ~So were calculated. The adsorption process was found to be feasible, endothermic and spontaneous. Both the mean free energy of adsorption and the activation energy values obtained shows that the adsorption process follows a physiosorption mechanism.