THE POTENTIAL OF COBALT BIOACCUMULATION FROM AQUEOUS SOLUTIONS BY USING THE EXOPOLYSACCHARIDE PRODUCING BACTERIUM, Xanthomonas Campestris

The removal of cobalt (as a toxic metal of high environmental priority due to its toxicity) from dilute aqueous solutions has been studied in the present work. An exopolysaccharide (EPS) producing bacterium. Xanthomonas campestn's was tested for its Co tolerance. it not only could grow on medium containing cobalt as high as 100 mg l'1 but also showed enhanced exopolysaccharide production. 68% of cobalt was accumulated by both bacterial cells and EPS The bioaccumulation characteristics for cobalt with different types of biosorbents were studied. The data performed that the living cells of X. campestrfs had higher cobalt bioaccumulation capacity than nonliving cells. in addition. the mixtures of either living or nonliving cells with EPS lead to enhancement of cobalt removal. The cobalt bioaccumulation of the X. campastn's was influenced by the initial pH of solution, initial metal ion concentration. biosorbent typefconcentration. and biosorbent pretreatment. The results of this study demonstrated that the living cells of this bacterial strain could remove cobalt from solution with relatively high efficiency. which reached to 80 mg cobalt g"l biosorbent.