Accumulation of Cu by Microalgae Scenedesmus obliquus and Synechocystis sp. PCC 6803

This study focused on the use of microbial potential for metal ion removal. Scenedesmus obliquus and Synechocystis sp. PCC 6803 were compared for accumulation of Cu in batch mode. During time course accumulation, S. obliquus accumulated Cu up to 124 μg mg -1 dry wt after 1h of incubation, whereas for Synechocystis sp. PCC 6803 it reached up to 64.9 μg mg -1 dry wt after 2h. Low biomass concentration were found more efficient in accumulating Cu with a value of 178 μg Cu mg -1 dry wt at 0.3 mgL -1 biomass concentrations of S. obliquus. However, for Synechocystis sp. PCC 6803 the maxima was reached at 0.6 mgL -1 of biomass concentration. Cu accumulation reached steady-state at a concentration of 1.5 μg mL -1 Cu in the external medium for Synechocystis sp. PCC 6803, whereas for S. Obliquus the steady-state was achieved at 2.5 μgmL -1 Cu. Maximum accumulation was observed between pH ranges of 5-7. Adsorption isotherm study depicted Freundlish model for S. obliquus, where as binding in Synechocystis sp. PCC 6803 followed the Langmuir model. As Freundlich principle indicates a reversible binding, which is regulated by van der Waals forces, it is obvious that the desorption/ recovery of the adsorbed metals could be much easier as compared to Langmuir binding, which is guided by chemical forces. Thus, this study suggests that the biomass of S. Obliquus hold immense potential for use as biosorbent in the removal/ recovery of heavy metal ions.