Bioaccumulation of Heavy Metals by Green Algae

Abstract

The biosorption of metal ions (Cr⁺³, ${\text{Cr}}_{{\text{2}}} {\text{O}}^{{ - 2}}_{7}$, Cu⁺², and Ni⁺²) on two algal blooms (designated HD-103 and HD-104) collected locally was investigated as a function of the initial metal ion concentration. The main constituent of HD-103 is Cladophora sp., while Spirulina sp. is present significantly in the bloom HD-104. Algal biomass HD-103 exhibited the highest Cu⁺² uptake capacity (819 mg/g). This bloom adsorbed Ni⁺² (504 mg/g), Cr⁺³ (347 mg/g), and ${\text{Cr}}_{{\text{2}}} {\text{O}}^{{ - 2}}_{7}$ (168 mg/g). Maximum of Ni⁺² (1108 mg/g) is taken by HD-104. This species takes up 306, 202, and 576 mg/g Cr⁺³, ${\text{Cr}}_{{\text{2}}} {\text{O}}^{{ - 2}}_{7}$, and Cu⁺², respectively. Equilibrium data fit very well to both the Langmuir and the Freundlich isotherm models. The sorption process followed the Freundlich model better. Pseudo-first-order kinetic model could describe the kinetic data. Infrared (IR) spectroscopic data were employed to identify the site(s) of bonding. It was found that phosphate and peptide moieties participate in the metal uptake by bloom HD-103. In the case of bloom HD-104, carboxylate and phosphate are responsible for the metal uptake. The role of protein in metal uptake by HD-103 was investigated using polyacrylamide gel electrophoresis.