Selective Biosorption of Lanthanide (La, Eu, Yb) Ions by Pseudomonas aeruginosa

The ability of Pseudomonas aeruginosa to adsorb selectively La3+, Eu3+, and Yb3+ from aqueous solution was investigated. The lanthanide biosorption equilibrium obeyed the Brunauer−Emmett−Teller isotherm model, indicating multilayer adsorption. Determined levels of maximum adsorption capacities were 397 μmol/g for lanthanum, 290 μmol/g for europium and 326 μmol/g for ytterbium (±10%). The results indicated that there were about 100 preferential sites for lanthanum per g of dry biomass. Experiments with mixed-cation solutions showed that the sequence of preferential biosorption was Eu3+ = Yb3+ > La3+. Biomasses dried at 37 and 70 °C showed the same selective behavior as wet biomass. Inert microbial biomass dried at 37 °C appeared to be the most efficient form for experimental use. The uptake of lanthanide by P. aeruginosa cells was not affected by the presence of sodium, potassium, calcium, chloride, sulfate and nitrate ions. Aluminum was a strong inhibitor of lanthanide ions biosorption. 87% of the total Al3+ was removed from the 3 mM solution, whereas only 8%, 20% and 3% of the total La3+, Eu3+, and Yb3+, respectively, were sorbed from 3 mM solutions. The results suggested that cells of Pseudomonas aeruginosa may find promising applications for removal and separation of lanthanide ions from aqueous effluents.