Biosorption of Cadmium by Waste Shell Dust of Fresh Water Mussel Lamellidens marginalis: Implications for Metal Bioremediation

The ability of the shell dust of freshwater mussel Lamellidens marginalis (MSD) to remove cadmium from the aquatic system was evaluated. The results indicate that MSD, a waste biomaterial, bears the potential to remove cadmium from contaminated water with a biosorption capacity of 18.18 mg g –1 at pH 6. At equilibrium, the adsorption data fitted to Langmuir ( r 2 = 0.992) significantly more than the Freundlich equation ( r 2 = 0.66). Regression analysis suggests that the biosorption kinetics followed the pseudo-second-order model ( r 2 = 0.999) better than the Lagergren model ( r 2 = 0.879). The possible mechanism of biosorption appeared to be ion exchanges with Fe, Al, Si, In, Co, and Ca ions together with binding of different functional groups such as −OH, −C═O, −C═C, and −C–C, as revealed through FTIR and EDX analyses. Although low in comparison to cadmium, the MSD-adsorbed zinc ( q max = 10.64 mg g –1 ) and lead ( q max = 8.06 mg g –1 ) varied in amounts, depending upon the initial metal ion concentration and biomass of the adsorbent. These observations substantiate MSD as a low cost and environment friendly biosorbent for heavy metal ion bioremediation.