Cadmium removal by immobilized scytonema sp. and hapalosiphon hibernicus

Abstract

Cadmium removal from aqueous solution (1 mg/l) was investigated in Scytonema sp. and Hapalosiphon hibernicus on eight types of immobilized material as loofa sponge(LS), delicate duty scour pad (DP), synthetic fiber (SF), polyethylene terepthalate (PET), polyethylene terepthalate (PET non-woven fabric), polyethylene (PE), polypropylene (PP) and polyurethane (PU). The results showed that immobilized cells on SF and free cells of Scytonema sp. and Hapalosiphon hibernicus had high cadmium removal rates at 93%, 95% and 85%, 98%, respectively. Immobilizing ability and dry weight per surface area (DW/SA) were 96%, 0.003 g cell/ cm3 and 97%, 0.0023 g cell/cm3 for Scytonema sp. immobilized on PET and Hapalosiphon hibernicus immobilized on SF, respectively. Immobilized cells on SF and PET, and free cells of Scytonema sp. had maximum adsorption capacities (qmax) at 26.74, 37.74 and 31.95 mg/g dry wt. and binding constants (kb) at 6.45, 2.14 and 2.70 l/mg, respectively when R2>0.96, while immobilized cells on SF and PET, and free cells of Hapalosiphon hibernicus had qmax values at 57.80, 64.52 and 59.17 mg/g dry wt. and kb values at 1.57, 2.07 and 1.50 l/mg. respectively when R2>0.99. The ultra-structural changes of both strains exposed to 1 mg/l of cadmium were observed under a transmission electron microscope. Cells were damaged and convoluted in the cell surface and intra-cellular organelles. Electron dense particles deposited in the cell walls and internal organelles of Hapalosiphon hibernicus indicated that cadmium uptake was probably by adsorption mechanism in cell membranes and accumulated in the intra-cellular organelles. Immobilized cells of Scytonema sp. and H. hibernicus on SF and PET have the potential to remove cadmium in wide spread low cadmium contaminated natural water such as in rivers or channels and can be applied in shrimp ponds. Copyright © Enviromedia.