Evaluation of the potential of microalgae Microcystis novacekii in the removal of Pb super(2+) from an aqueous medium

In this study, the absorption capacity of active and inactive biomass of the microalgae Microcystis novacekii to remove Pb super(2+) from aqueous solutions was investigated. This is the first reported study of biosorption by a cyanobacterium species, which is abundant and easily found in eutrophic lakes and ponds in tropical areas of the world. We also evaluated the effects of different concentrations of Pb super(2+) on growth rates of M. novacekii. Inactive biomass was characterized by elemental composition, surface area, potentiometric titration, infrared spectroscopy and thermogravimetric analysis (TGA). The biosorption data of Pb super(2+) by inactive biomass were analyzed using the Langmuir and Freundlich isotherms. Pb super(2+) concentrations higher than 0.5mg L super(-1) inhibited species growth. Potentiometric titrations showed a significantly higher negative surface charge (1.48 plus or minus 0.22mmol g super(-1)) with two acidic groups (pK sub(1) =3.74 plus or minus 0.12 and, pK sub(2) =7.25 plus or minus 0.30). Analysis of inactive M. novacekii cells by infrared spectroscopy suggests that the cell wall carboxyl and amide groups participate in Pb super(2+) biosorption. The maximum Pb super(2+) adsorbed was found to be 70mg g super(-1), and the biosorption of Pb super(2+) on inactive M. novacekii correlated well (R super(2) =0.931) with the Langmuir equation compared to the Freundlich isotherm equation (R super(2) =0.823) in the concentration range studied.