RESUMO
Powdered activated carbon (PAC) prepared from Eucalyptus camaldulensis Dehn. bark was tested for its adsorption capacity for Cu(II) and Pb(II). The experiment was conducted to investigate the effects of pH, contact time, initial metal concentration, and temperature. The best adsorption of both Cu(II) and Pb(II) occurred at pH 5, where the adsorption reached equilibrium within 45 min for the whole range of initial heavy metal concentrations (0.1-10 mmol/L). The adsorption kinetics was found to follow the pseudo-second order model where equilibrium adsorption capacities and adsorption rate constants increased with initial heavy metal concentrations. The adsorption isotherm followed Langmuir better than Freundlich models within the temperature range (25-60 degrees C). The maximum adsorption capacities (qm) occurred at 60 degrees C, where qm for Cu(II) and Pb(II) were 0.85 and 0.89 mmol/g, respectively. The enthalpies of Cu(II) and Pb(II) adsorption were 43.26 and 58.77 kJ/mol, respectively. The positive enthalpy of adsorption indicated an endothermic nature of the adsorption.
