BIOSORPTION SITES OF SELECTED METALS USING ELECTRON-MICROSCOPY

Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray (ED AX) microanalysis on selected metal bearing biomass samples of three m icrobial strains, BP 7/26 Arthrobacter sp., ER 121 Alkaligenes eutroph us, and AS 302 Pseudomonas mendocina, were performed in order to obtai n information concerning the localisation of the metals Palladium, Sil ver, Yttrium, and Nickel in the different parts of the cells. Signific ant differences have been observed concerning the localisation of each metal. The results obtained by TEM and EDAX microanalysis show that a lthough the strains examined present different characteristics, the ob served localisation of the biosorbed metals could be metal rather than strain dependent. This work, combined with systematic experimental wo rk on the determination of biosorption isotherms and metal uptake capa cities for each of the above strains, as well as overall kinetics of t he process, is a first step in the attempt to determine the active bin ding sites of the biomass types examined and, consequently, to elucida te the underlying mechanism of the sorption of the above metals by the biomass. (C) 1997 Elsevier Science Inc.