Adsorption Kinetics and Thermodynamics of Malachite Green Dye 5 Adsorption Kinetics and Thermodynamics of Malachite Green Dye onto Calatropis Gigantis Bark Carbon

The removal of toxic dye such as malachite green from waste water by adsorption using activated carbons received much interest. However, the success of this approach depends on economic feasibility, which can be obtained by optimization of the environmental conditions. This paper evaluates the use of low cost Calatropis gigantis bark carbon to eliminate malachite green from aqueous solutions. The effect of some parameters studied shows that the maximum sorption capacity was reached within 40 minutes. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. The temperature variation study showed that the malachite green adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the malachite green solutions. The Langmuir and Freundlich adsorption isotherms obtained, positive êH0 value, pH dependent results and desorption of malachite green in mineral acid suggest that the adsorption of malachite green on Calatropis gigantis bark carbon involves physisorption mechanism.