Metal Sorption by Microalgae for Employment in Biotreatment of Environmental Heavy Metal Contamination

Abstract

The study on the ability of microalgae to accumulate heavy metal pollutants from surrounding environments is important in understanding both the basic mechanism and its application in the biotreatment of heavy metal contamination. The present work reports the results on the biosorption of heavy metals of environmental concern namely chromium, cadmium and lead by the living as well as the nonliving cells of the blue green alga Hapalosiphon stuhlmannii Hieron. and the green alga Scenedesmus quadricauda (Turp.) de Breb. The metal sorption was measured under controlled conditions in which the algal cells were exposed over specified time to different metal concentrations in the range of 0.1–15 .0 µg/ml. The metal sorption by both the living as well as the nonliving algal cells generally increased with the metal concentration and followed the Freundlich isotherm model over the concentration range investigated in the experiments. The sorption capacity for the living as well as the nonliving cells of H. stuhlmannii for the different metals was found to be in the order Pb>Cd>Cr, whereas that for the living cells of S. quadricauda was found to be in the order Pb>Cr>Cd and for the nonliving cells, to be in the order Pb>Cd>Cr. Further the sorption intensity for the living as well as the nonliving cells of H. stuhlmannii for the different metals was found to be in the order Cd>Cr>Pb, whereas that for the living cells of S. quadricauda was found to be in the order Cd>Cr>Pb and for the nonliving cells, to be in the order Cd>Pb>Cr. The variations in the metal sorption by the different algal cells were attributed to the varied physicochemical properties of the cell walls to bind the different metals.