A carbonaceous adsorbent prepared from an indigenous waste Azadirachta indica bark (AIC), by acid treatment was tested for its efficiency in removing Rhodamine B (RDB) dye. 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 plots with temperature variation study showed that the Rhodamine B 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 Rhodamine B solutions. Almost 94% removal of Rhodamine B was observed at 50 °C. Thermodynamic parameters such as H°, S°, G° were evaluated. The positive Ho value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of RDB on AIC involves physisorption mechanism. The adsorption of RDB on to the surface of AIC has been confirmed by the analysis of IR spectra, XRD and SEM images before and after RDB adsorption. The adsorbent was found to be both effective and economically viable.
