Kinetic analysis of reactive blue 221 adsorption on kaolinite

The use of cheap, efficient and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study has investigated the potential use of kaolinite as alternative adsorbent for the removal of reactive blue 221 from wastewater. Therefore, a series of kinetic experiments were conducted in a batch system to assess the effect of the system variables, i.e. stirring speed, contact time, initial dye concentration, initial pH. temperature and acid-activation. The adsorption rate increased with the increasing initial dye concentration, ionic strength, solution temperature and acid-activation, but decreased with an increase in pH. The stirring speed had no important effect on the adsorption rate. The rates of adsorption were found to conform to the pseudo-second-order kinetics with a good correlation. In addition, various thermodynamic activation parameters, such as Gibbs free energy, enthalpy, entropy and the activation energy were calculated. The adsorption process of reactive blue 221 on kaolinite was found to be not a spontaneous and endothermic process. (C) 2010 Elsevier B.V. All rights reserved.