Selective biosorption of lanthanide (La, Eu, Yb) ions by an immobilized bacterial biomass
Résumé
The removal of metallic ions La3+, Eu3+ and Yb3+ from aqueous solution by immobilized biomass of Pseudomonas aeruginosa was investigated in batch and column reactors. Batch studies consisted in kinetic measurements for lanthanum adsorption by biomass-chitosan beads. Results did not show a significant effect of the presence of bacteria into chitosan matrix on the lanthanum uptake. Then, laboratory scale fixed-bed column experiments were carried out using biomass-entrapped polyacrylamide gel beads, which contained approximately 48% (dry weight basis) of biomass. The lanthanum sorption was dependent on the superficial liquid velocity based on empty column in the range 0.76-2.29 m.h(-1). The removal of lanthan decations (2 mM) at pH 5.0 and 0.76 m/h was 198 mu mol.g(-1) (dry biomass) for lanthanum, 167 mu mol.g(-1) for europium and 192 mu mol.g(-1) for ytterbium (+/-10%). These results are of the order of 1.7-2 times lower than those observed in batch systems with free bacterial cells. Column experiments with mixed-cation solutions showed the following sequence of preferential biosorption: Eu3+ > Yb3+ > La3+.
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