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

Abstract

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.