游离和固定化Synechococcus sp.细胞对Pb(II)和Cr(VI)生物吸附性能的比较研究

he comparative study on adsorptions of Pb (II) and Cr (VI) ions by free cells and immobilized cells of Synechococcus sp. were performed, in which different aspects including zeta potential of the cells, the influence of pH, temperature and initial concentration of metal ions, as well as adsorption kinetics were referred. The lyophilized free cells had a surface isoelectric point (IEP) of 3, below and above that point, the adsorption features of Cr (VI) and Pb (II) were just contrary to each other, indicating of an electrostatic adsorption feature of Cr (VI) and Pb (II). The immobilization of the free cells by Ca-alginate did not significantly modify the surface properties and affect the adsorption features of the biosorbent. The absorption processes of Cr (VI) and Pb (II)on both the free and immobilized cells that were apparently affected by pH and the initial concentration of metals ions in the bulk solution, but were much weakly affected by temperature in the test range of 10-50ºC, were very fast in the early several minutes, in which more than half of saturation adsorption could be attained, and after which was followed by a slower stage that approximately observed the 1st order kinetic model. On to both the free and immobilized cells biosorbents, the adsorption of Pb (II) observed both Langmuir and Freundlich isotherm models, and that of Cr (VI) obeyed only Freundlich model, in the tested range of initial concentration of Cr (VI) and Pb (II) 0-700 mg.l-1.