Selective biosorption of lanthanide (La, Eu, Yb) ions by an immobilized bacterial biomass

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 lanthanide cations (2 mM) at pH 5.0 and 0.76 m/h was 198 μmol.g^-1 (dry biomass) for lanthanum, 167 μmol.g^-1 for europium and 192 μmol.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-cationsolutions showed the following sequence of preferential biosorption: Eu³⁺ >Yb³⁺ >La³⁺.