Comparative study on the adsorption capacity and kinetics of xylene onto rice husk and cassava peel activated carbon

This study focuses on the comparative adsorption of xylene from aqueous media onto cassava peel activated carbon (CPAC) and rice husk activated carbon (RHAC). Ash content, bulk density, iodine number, moisture content, pH, point of zero charge, and % carbon yield of the prepared CPAC and RHAC were reported. To evaluate the removal of xylene, adsorption activities of CPAC and RHAC were monitored under different experimental conditions: adsorbent dose, contact time, pH as well as initial xylene concentration. The adsorption capacity and kinetics depended on the properties of the activated carbons, the adsorbate and the prevailing adsorption milieu while the equilibrium and rate of adsorption were adequately interpreted by Langmuir and pseudo-first-order models respectively. Batch adsorption kinetic experiments revealed that the adsorption of xylene onto CPAC and RHAC involved fast and slow processes. At optimal conditions of 8 mg/L xylene in contact with 0.1 g of adsorbents for 150 min at pH 7.5, the quantity of xylene adsorbed onto RHAC and CPAC were 46.7 mg/g and 53.3 mg/g in that order. Thermodynamic study showed the adsorption process of xylene onto CPAC and RHAC to be non-spontaneous but ΔH was negative.