Biosorption of Cadmium from Aqueous Solution by Shell Dust of the Fresh Water Snail Melanoides tuberculata

ABSTRACT The metal bioadsorption potential of shell dust of the freshwater snail Melanoides tuberculata (MTSD) was evaluated under laboratory conditions using cadmium as a model metal. As bioadsorbent, MTSD exhibited a biosorption capacity of 27.03 mg g^?1 at pH 6, indicating potential to remove cadmium from aqueous solution. The adsorption data fit more to the Langmuir (R² = 0.998) equation than the Freundlich (R² = 0.761) equation at equilibrium condition. The kinetics of biosorption followed the pseudo-second-order model (R² = 0.999) better than the Lagergren model (R² = 0.676), as was evident from the regression analysis. The presence of calcium ions appears to have facilitated ion exchange with cadmium along with the binding of different functional groups, as revealed through Fourier transform infrared (FT-IR) analysis. It is apparent from these observations that MTSD can act as low-cost and efficient bioadsorbent for cadmium bioremediation from aquatic habitats. Use of the shells of M. tuberculata for metal biosorption will promote the utility of a waste material of biological origin for bioremediation of heavy metals such as cadmium.