Adsorption of methyl violet from aqueous solution by polyacrylamide as an adsorbent: Isotherm and kinetic studies

In this study, polyacrylamide was utilized as a potential adsorbent for the removal of textile dye methyl violet (MV). The optimum conditions for adsorption by using a batch method were evaluated by changing various parameters such as contact time, adsorbent dose, initial pH of the solution and temperature. The adsorption equilibrium was well described by the Langmuir isotherm model with maximum adsorption capacity of 1136 mg g(-1) of methyl violet on polyacrylamide (PAA). The observed increase in adsorption with increasing temperature suggests that the adsorption of dye on polyacrylamide is endothermic in nature. Methyl violet adsorption followed pseudo-second-order rate kinetics. From kinetic studies, various rates and thermodynamic parameters such as enthalpy, free energy and entropy changes were calculated and these values show that the MV-PAA adsorption process was favored at high temperatures. (c) 2010 Elsevier B.V. All rights reserved.