Novel Lignocellulosic Wastes for Comparative Adsorption of Cr(VI): Equilibrium Kinetics and Thermodynamic Studies

Cr(VI) adsorption onto Eucalyptus camaldulensis sawdust (ECS) waste was investigated in batch and column reactors. Various parameters, including the adsorbent dose, pH, initial concentration, particle size, contact time and temperature were optimized. The maximum adsorption capacity (35.58mg g-1, 71.16%) was achieved at pH 2.0. Data fitted well to Freundlich and Halsey’s models (R2=0.992), indicating the multilayer adsorption of Cr(VI). It obeys the pseudo-second order kinetics. Endothermic and non-spontaneous nature of Cr(VI) adsorption was observed with positive values of changes in enthalpy (9.83 kJ mol-1), and Gibbs-free energy (1.52, 1.38, 1.24, 1.10 and 0.97 kJ mol-1), respectively. In this column study, the breakthrough curve time increased from 670 to 1,270min by increasing the bed height from 5 to 15 cm, respectively. Column data was found well fitted to bed depth service time model. Adsorption capacity at 60% breakthrough was 2,443.636mg L-1. The study indicates that ECS waste can be a promising adsorbent for Cr(VI) remediation from industrial effluents.