Adsorption, kinetic and equilibrium studies on removal of basic dye from aqueous solutions using hydrolyzed Oak sawdust

Oak sawdust (SD), which is the main waste from furniture industry in Egypt, has been used as an adsorbent without treatment or it was treated with 0.1 N sodium hydroxide (SD1) and 0.1 N sulphuric acid (SD2). Different adsorbents were characterized by SEM, TGA and FTIR to clarify the effect of treatment on the adsorption process. Oak sawdust and different treated Oak sawdust have been used for the removal of methylene blue dye from aqueous solutions. Batch adsorption experiments were performed as a function of pH, adsorbent dose, agitation speed, contact time and initial dye concentration. The optimum pH required for maximum adsorption was found to be 8. The experimental equilibrium adsorption data are tested for Langmuir, Freundlich and Temkin isotherms. Results indicate the following order to fit the isotherms: Langmuir > Temkin >>> Freundlich adsorption. Kinetics data were modeled using the pseudo-first and pseudo-second order, Elovich equations and intra-particle diffusion models. The results indicate that the second-order model best describes adsorption kinetic data with regard to the intra-particle diffusion rate. Thermodynamic parameters Delta H, Delta S and Delta G have been calculated for each type of adsorbents. Positive value of Delta H and negative value of Delta G show endothermic and spontaneous nature of adsorption respectively, also activation energy Ea has been calculated.