KINETIC AND ADSORPTION EQUILIBRIUM STUDIES FOR REMOVAL OF TEXTILE DYE FROM AQUEOUS SOLUTIONS ON NUT SHELL ADSORBENT

In the present work, the objective has been to determine the potential of a natural residue material, namely, nut shells, for the removal of Methylene blue dye from aqueous solutions. Adsorption studies were carried out varying parameters, such as contact time, pH, initial concentration and temperature, in order to find the optimum ones. The results obtained showed that the nut shell adsorbent had an adsorption capacity of 16.44 mg/g for Methylene blue. The adsorption process was rapid and reached equilibrium in 20 min of contact at 45 degrees C and pH 6. Different adsorption models, namely, the Langmuir, Freundlich, Temkin and Elovich ones, were examined for the description of the adsorption data, and it was found that the best fit of experimental data was achieved by the Langmuir model. Also, the pseudo-firstorder and pseudo-second-order kinetic models were applied to the experimental data. The experimental data fitted very well the pseudo-second-order kinetic model and followed the model of intraparticle diffusion (Kdif varied from 1.694 to 3.584 mg/(g min(1/2)) for concentrations between 30 and 70 mg/L, whereas diffusion was not the only rate-limiting step. The adsorption using the studied system (nut shells/Methylene blue) proved to be an exothermic and spontaneous process. The biosorbent was characterized by various techniques, including FT-IR and XRD.