Available online at www.scholarsresearchlibrary.com Scholars Research Library Archives of Applied Science Research, 2011, 3 (3):154-166 (http://scholarsresearchlibrary.com/archive.html) ISSN 0975-508X CODEN (USA) AASRC9 154 Scholar Research Library Kinetic and equilibrium studies of Rhodamine B adsorption by low cost activated carbon A. Jafar Ahamed 1* , V. Balakrishnan 2 and S. Arivoli 3 1 PG and Research Department of Chemistry, Jamal Mohamed College (Autonomous), Affiliated to Bharathidasan University, Tiruchirappalli, Tamil Nadu, India 2 Department of Chemistry, Dr. Ambetkar Government Arts College, Viyasarpadi, Chennai, Tamil Nadu, India 3 Department of Chemistry, T.V.K.Government Arts College, Thiruvarur, Tamil Nadu, India ______________________________________________________________________________ ABSTRACT 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 (Q m ) 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 H o 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. Key words: Azadirachta Indica, Rhodamine B, Adsorption isotherm, Equilibrium, Kinetic and Thermodynamic parameters, Intraparticle diffusion, Regeneration pattern. ______________________________________________________________________________ INTRODUCTION Color is one of the characteristics of an effluent. This can be easily detected and readily traced back to its source. Most of the dyes are stable to biological degradation. Colored waters are often objectionable on aesthetic grounds for drinking and other agricultural purposes. Wastewaters from dyeing industries are released in to nearby land or rivers without any treatment, because the conventional treatment methods are not cost effective in the Indian