Aims: This study aimed to unveil perrhenate sorption properties of the filamentous sheaths formed by Sphaerotilus montanus, Sphaerotilus natans and Thiothrix fructosivorans.
Methods and results: The adsorptions of perrhenate on lyophilizates of the above-mentioned filamentous sheaths were analysed by ICP, IR, XPS and EDX. The capacity reached 82 mg per g-adsorbent, when using S. natans. The Langmuir coefficient of this adsorbent was found to be the largest of the three. The adsorption capacity was discussed with respect to the amount of nitrogen and phosphorus in the adsorbents. The occurrence of anion exchange was implied by the IR spectrum changes before and after adsorption. The adsorption data fitted well with a pseudo-second-order equation, suggesting that the rate is determined by the chemical bond formation.
Conclusions: A significant amount of perrhenate was adsorbed on the sheaths formed by S. montanus, S. natans and T. fructosivorans. The adsorption was correlated with the elemental compositions. A strong chemical bond formation was suggested from the results of the Langmuir adsorption isotherm and kinetic analysis.
Significance and impact of study: The capacity obtained for S. natans is one of the largest adsorptions amongst the similar biomaterials, implying the possibility of providing economical adsorbents of rare metal oxyanions.
Keywords: adsorption; lyophilized bacteria; rhenium removal; sheath-forming bacteria.
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