Kinetic, isotherm, and thermodynamic studies of Reactive Orange 13 adsorption onto activated carbon obtained from orange pulp

Abstract

Orange (Citrus sinensis L.) pulp, solid waste resulting from the production of citrus juice, was developed into activated carbon using zinc chloride at a 3:1 impregnation ratio with an activation temperature of 500 degrees C. To determine the adsorption capacity, the prepared activated carbon was then utilized for the removal of dyestuff (Reactive Orange 13) from aqueous solutions. The resulting activated carbon had a high specific surface area of 1,779.48 m(2) g(-1). The experimental isotherm data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The experimental kinetic data were analyzed using the pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich models. The results obtained from the isotherm and kinetic studies were well explained, respectively, by the Langmuir and pseudo-second-order models. Thermodynamic parameters were computed, and the results obtained revealed that the present adsorption is a spontaneous and endothermic adsorption process. These findings indicate that orange pulp activated carbon can be effectively utilized as an inexpensive adsorbent to remove dyestuff from an aqueous solution.