Development of new adsorbents for heavy metals using microorganisms and their microcharacterization.

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Microorganisms, such as Streptomyces levoris and Arthrobacter nicotianae, were found to have high abilities to sorb uranium, thorium and copper. Immobilized persimmon tannin has also have high affinities for vanadium and chromium. Thus, both biosorbents could be used for hevy metal recovery and removal from aqueous systems. The ESR study on biosorption gave us that microscopic circumstances, such as pH, around copper in microbial cells affected on the chemical state of copper, and that vanadium should be adsorbed on the immobilized persimmon tannin gels through the reduction process. The rise and fall of activated oxygens, such as hydroxy radical, in metal (Cu(II), V(IV) and U(VI))-H_2O_2 systems, was affected by microbial cells and tannin compounds through their masking and anti-oxidant effects. Thus, these effects could be used for the microcharacterization of the biosorbents. In order to evaluate the heavy metal stress in biosystems, some ESR techniques, such as the ESR on-line measurements using microdialysis and the ESR imaging using spin probes, was established. The interaction between spintraps and heavy metal ions was also examined. These results were publishe as 23 papers in several journals and presented as 33 papers in the international and domestic meetings.