Removal of Cd(II) from aqueous solution using blue pine sawdust: Equilibrium, kinetics and thermodynamic studies

The adsorption of Cd(II) ions onto sawdust has been investigated in detail as a function of equilibration time (1-120 min), dosage of adsorbent (0.025-0.5 g)/10 ml, concentration of Cd(II) (9-1780 mu M) and of nature (pH 1-10). Maximum adsorption (ca. 95.3%) is achieved from deionised water in 30 minutes at pH 7 using 0.2 g adsorbent/10 ml adsorbate solution. The adsorption data follow Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms over the entire range of Cd(II) ions concentration examined and their characteristic constants have also been evaluated. The variation of adsorption with temperature has yielded Delta H, Delta S and Delta G values for the 18 mu M cadmium concentration. The kinetics of adsorption obeys Morris-Weber and Lagergren equations. The first order rate constant and the intraparticle diffusion rate have also been estimated. Sawdust appears to have potential to remove Cd(II) ions from aqueous solutions at trace or subtrace concentration, to preconcentrate or treat industrial wastewater.