Removal of Phenol from Paint Wastewater by Adsorption onto Phosphoric Acid Activated Carbon Produced from Coconut Shell: Isothermal and Kinetic Modelling Studies

Abstract

The feasibility of using phosphoric acid activated carbon produced from coconut shell to remove phenol from paint wastewater under batch mode was investigated. The results showed that adsorption of phenol was contact time, adsorbent particle size and adsorbent dosage dependent. The batch equilibrium adsorption data were analyzed by two-parameter adsorption isotherm models of Langmuir and Freundlich using the linear regression method. Both isotherm models fitted very well to the equilibrium adsorption data, however, the Freundlich isotherm equation provided the best model to describe the adsorption of phenol onto coconut shell activated carbon. Adsorption capacity of 2.01 mg/g and adsorption intensity of 1.07 was obtained for granular coconut shell activated carbon and corresponding 3.63 mg/g and 1.55 for powdered coconut shell activated carbon at 30 ^oC. The adsorption kinetic data were fitted to three adsorption kinetic models (pseudo first-order, pseudo second-order and intra-particle diffusion) using the linear regression method. The three kinetic models fitted well to the adsorption kinetic data; however, the pseudo second-order kinetic model gave the best fit and the adsorption mechanism was controlled by film diffusion. Thus, phosphoric acid activated carbon produced from coconut shell has the potential for application as an effective adsorbent for phenol removal from wastewater.

Keywords: Activated carbon; Adsorption isotherms; Adsorption kinetics; coconut shell; paint wastewaters.