Evaluation of the potential of microalgae Microcystis novacekii in the removal of Pb2+ from an aqueous medium

Abstract

In this study, the absorption capacity of active and inactive biomass of the microalgae Microcystis novacekii to remove Pb(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(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(2+) by inactive biomass were analyzed using the Langmuir and Freundlich isotherms. Pb(2+) concentrations higher than 0.5 mg L(-1) inhibited species growth. Potentiometric titrations showed a significantly higher negative surface charge (1.48+/-0.22 mmol g(-1)) with two acidic groups (pKa(1)=3.74+/-0.12 and, pKa(2)=7.25+/-0.30). Analysis of inactive M. novacekii cells by infrared spectroscopy suggests that the cell wall carboxyl and amide groups participate in Pb(2+) biosorption. The maximum Pb(2+) adsorbed was found to be 70 mg g(-1), and the biosorption of Pb(2+) on inactive M. novacekii correlated well (R(2)=0.931) with the Langmuir equation compared to the Freundlich isotherm equation (R(2)=0.823) in the concentration range studied.