Sawdust-A green and economical sorbent for the removal of cadmium (II) ions

The ability of sawdust (treated and untreated) waste, a waste material derived from the commercial processing of cedrus deodar wood for furniture production, to remove/preconcentrate Cd(II) ions from aqueous solution was determined. Sorption was found to be rapid (∼97% within 8 min). The binding of metal ions was found to be pH dependent, optimal sorption accruing at around pH 4-8. Potentiometric titrations of sawdust revealed two distinct pKa values, the first having the value similar to carboxylic groups (3.3-4.8) and second comparable with that of amines (8.53-10.2) with the densities 1.99 × 10−4 and 7.94 × 10−5, respectively. Retained Cd(II) ions were eluted with 5 ml of 0.1 mol l−1 HCl. Detection limit of 0.016 μg ml−1 was achieved with enrichment factors of 120. Recovery was quantitative using sample volume of 600 ml. The Langmuir and D-R isotherm equations were used to describe partitioning behavior for the system at different temperatures. Kinetic and thermodynamic behavior of sawdust for Cd(II) ions removal was also studied.