Abstract
Adsorption of a cationic dye, methylene blue, from aqueous solutions by using sawdust (without any modification) by batch
adsorbers was investigated. The surface characterization of the saw dust was carried out by Fourier transform infrared (FTIR) and
scanning electron microscopy (SEM) and pHzpc of the surface was also determined. Effects of different parameters such as
contact time and initial concentration, temperature and pH on the process of removal were studied. The process of removal was
found to be very fast and equilibrium was established in 35 min. The maximum removal efficiency obtained was 94.47 % at pH
3.0, 30 oC, 20 mg L−1 initial concentration and a 10 g/l adsorbent dose. The mechanism for the removal of dye from aqueous
solutions was investigated. The maximum removal of methylene blue was obtained at pH 3.0. The kinetic data was in close
agreement with pseudo-second-order than pseudo-first-order expression for the removal of methylene blue onto sawdust.
Equilibrium isotherms were analyzed by Langmuir and Freundlich adsorption models. Values of the thermodynamic parameters
namely changes in free energy (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) for the process of removal have been determined. The
results indicate that sawdust could be effectively employed as adsorbent material for the removal of methylene blue from
aqueous solutions.