Factors influencing the biosorption of gadolinium by micro-organisms and its mobilisation from sand

The present work was devoted to the study of the biosorption capacities of various microbial species (Bacillus subtilis, Pseudomonas aeruginosa, Ralst onia metallidurans CH34 previously Alcaligenes eutrophus CH34, Mycobacteriu m smegmatis, Saccharomyces cerevisiae) for ions of the lanthanide gadoliniu m (Gd3+). The uptake by sand of this element was also measured. Saturation curves and Scatchard models were established for all biosorbants used in th is work. The results enabled us to determine the binding affinities and the maximum capacities for biosorption of Gd3+, which ranged from 350 mu mol g (-1) for B. subtilis to 5.1 mu mol g(-1) for S. cerevisiae. This study demo nstrated the usefulness of optimisation of experimental conditions in bioso rption investigations. Experimental results showed that biosorption could b e influenced by the growth stage and by the composition of the growth mediu m of microbial cells. Finally, particular attention was given to the transf er of gadolinium ions from a loaded sand to a bacterial suspension.