Bioaccumulation of heavy metals by green algae

The biosorption of metal ions ( Cr+3, Cr2O7-2, 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 Cr2O7-2 (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, Cr2O7-2, 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.