Biosorption of heavy metals influenced by the chemical composition of Spirulina sp. (Arthrospira) biomass.

The capacity of Spirulina sp. cells with different chemical composition for Pb (II), Cd (II) and Cr (VI) sorption, was evaluated. Four different types of Spirulina biomass with a different chemical composition were tested. Two of them contained a high percentage of protein (68.95 +/- 0.30 and 63.73 +/- 0.25%) as a result of being cultivated in Zarrouk medium and exposedat two light intensities (66 micromol photon m(-2) s(-1) and 144 micromol photon m(-2) s(-1)) in batch cultures. A third type of biomass, cultivated in a "Complex" medium and exposed at 66 micromol photon (m-2) s(-1), contained a high percentage of lipids (30.08 +/- 1.92. Finally, the fourth type of biomass was enriched in polysaccharides (25.54 +/- 0.51%) as a result of being cultivated in the "Complex" medium, but exposed at 144 micromol photon m(-2) s(-1). It was found that the chemical composition of Spirulina sp. cells did have a strong influence on their adsorption capacity. The maximum adsorption capacities (q(max)) for Pb and Cd were highest (172.41 and 54.05 mg g(-1) of cells, at pH 5.0 and 4.5 respectively) when cells exhibited the higher polysaccharide content. In the case of Cr VI, the highest q(max), was exhibited by cells cultivated in Zarrouk medium and showing the higher protein content (at pH 2.0). pH did not affect the adsorption of Pb II in the range of 3 to 5.5, nor of Cd in the range of 4 to 7. For Cr VI, adsorption was observed only at a pH equal to 2 or lower.