Sorption studies of Zn(II)- and Cd(II) ions from aqueous solution on treated sawdust of sissoo wood

Sawdust, an inexpensive material, has been utilized as an adsorbent for the removal of Zn(II)- and Cd(II)ions from aqueous solution. The effects of time of equilibrium, pH, temperatures and dosage of the adsorbent on the removal of Zn(II)- and Cd(II)ions have been studied. The equilibrium nature of Zn(II)- and Cd(II)ions adsorption at different temperatures (25-60 degrees C) has been studied. The percent adsorption of Zn(II)- and Cd(II)ions increased with an increase in pH, temperature and dosage of treated sawdust. The applicability of the Langmuir isotherm suggests the formation of monolayer coverage of Zn(II)- and Cd(II)ions at the surface of the adsorbent. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of Zn(II)- and Cd(II)ions has also been computed and discussed. The heat of adsorption [Delta H=17.706 kJmole(-1) for Zn(II) and Delta H=16.949 kJmole(-1) for Cd(II)] implied that the adsorption was an endothermic adsorption. The sawdust was found to be a metal adsorbent as effective as activated carbon.