Modeling of adsorption isotherms and kinetics of a tannery dye onto an activated carbon prepared from an agricultural by-product

The potential of an activated carbon prepared from an agricultural by-product for the removal of a tannery dye from aqueous solution was investigated. The effects of contact time, solution pH and temperature were evaluated. The results indicated that the equilibrium data were perfectly represented using a Langmuir isotherm. The maximum monolayer adsorption capacity was found to be 146.31 mg g- 1 at 25°C. The kinetic studies indicated that the adsorption process followed a pseudo-second-order model. The application of an intra-particle diffusion model revealed that the adsorption mechanism of the concerned dye is a rather complex process and that diffusion is involved in the overall rate of the adsorption process, but it is not the only rate-controlling step. The calculated thermodynamics parameters revealed the spontaneous and endothermic nature of the adsorption process. The activation energy, Ea = 9.50 kJ mol- 1, could indicate a physical adsorption process. Despite the presence of other components in the real effluent, the adsorbent was able to remove the target dye. The present study indicates that activated carbon prepared from olive-waste cakes is a promising candidate as a low cost adsorbent for the removal of a tannery dye from industrial wastewater. © 2012 Elsevier B.V.