Adsorption kinetics and thermodynamics of malachite green dye unto acid activated low cost carbon

A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Malachite green (MG). The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm) obtained from the Langmuir isotherm plot were 9.7377, 9.6246, 9.6339, 9.5693 mg/g respectively at an initial pH of 6.0 at 30, 40, 50 and 60°C. 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. Almost 80% removal of Malachite green was observed at 60°C. The type I and II isotherm obtained, positive ∆H° value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of Malachite green on PDC involves chemisorption as well as physisorption mechanism.