Abstract
The biosorption of cadmium(II) on live and dead biomass of Saccharomyces cerevisiaewas investigated with respect to the adsorption conditions. The biosorption mechanism was investigated by energy dispersive X-ray analysis (EDAX) and transmission electron microscope (TEM). The effects of the biosorbent dose, initial metal ion concentration, initial pH and contact time were studied. The optimum conditions for cadmium(II) biosorption were found to be 3 g/L, 250 mg/L and 6.0, respectively, for biosorbent dose, initial metal ion concentration and initial pH. Cadmium(II) biosorption by dead cells was a fast process. Under these conditions, the maximum biosorption capacity of the dead biomass was obtained to be 55 mg/g, while that of live biomass was 36 mg/g. TEM observations indicated the presence of cadmium (II) deposits intracellularly and extracellularly. EDAX examinations showed that cadmium(II) was exchanged with the element (aluminum) present on the surface of native cells of S. cerevisiae, thereby suggesting the occurrence of bioadsorption, ion exchange and complexation. Cadmium(II) biosorption capacity on dead cells was enhanced by ethanol treatment and alginate immobilization. Overall, the results showed that the ethanol-treated, alginate-immobilized biomass was capable of removing cadmium(II) from wastewater samples. Key words: Biosorption, Saccharomyces cerevisiae, cadmium(II), immobilization, chemical treatment.
Highlights
In recent years, heavy metal pollution has become one of the most serious environmental problems
The biosorption mechanism was investigated by energy dispersive X-ray analysis (EDAX) and transmission electron microscope (TEM)
S. cerevisiae was found to be resistant to cadmium(II) up to 900 mg/L using Yeast Extract Peptone Dextrose (YEPD) agar medium
Summary
Heavy metal pollution has become one of the most serious environmental problems. The presence of heavy metals even in traces is toxic and detrimental to both flora and fauna (Volesky, 1990). Cadmium(II) is produced solely as a by-product from the extraction of zinc and lead It is used in rechargeable batteries, specialized electronic equipment, bearing alloys, pigment (yellow and red) for ceramic glazes, paints and plastics. It is present in phosphate fertilizers and fungicides (Ayres, 1992). In 1997, cadmium(II) was ranked number 7 by the Agency for Toxic Substances and Disease Registry/Environmental protection Agency "Top 20 Hazardous Substances Priority List" (Liao and Freedman, 1998)
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