Biomass of a mercury‐resistant strain Pseudomonas aeruginosa PU21 (Rip64) and hydrogen‐form cation exchange resin (AG 50W‐X8) were investigated for their ability to adsorb mercury. The maximum adsorption capacity was approximately 180 mg Hg/g dry cell in deionized water and 400 mg Hg/g dry cell in sodium phosphate solution at pH 7.4, higher than the maximum mercury uptake capacity in the cation exchange resin (100 mg Hg/g dry resin in deionized water). The mercury selectivity of the biomass over sodium ions was evaluated when 50 mM and 150 mM of Na+ were present. Biosorption of mercury was also examined in sodium phosphate solution andphosphate‐buffered saline solution (pH 7.0), containing 50mM and 150 mM of Na+, respectively. It was found that the presence of Na+ did not severely affect the biosorption of Hg2+, indicating a high mercury selectivity ofthe biomass over sodium ions. In contrast, the mercury uptake by the ion exchange resin was strongly inhibited by high sodium concentrations. The mercury biosorption was most favorable in sodium phosphate solution (pH 7.4), with a more than twofold increase in the maximum mercury uptake capacity. The pH was found to affect the adsorption of Hg2+bythe biomass and the optimal pH value was approximately 7.4. The adsorption of mercury on the biomass and the ion exchange resin appeared to follow theLangmuir or Freundlich adsorption isotherms. © 1994 John Wiley & Sons, Inc.
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