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The search for alternative sources of recovery and separation of pure rare earth elements (REE) is a priority and strategic action by several countries demanding these elements. As an alternative to classical processes of extraction of REE, the biosorption process has been evaluated in a combination between biotechnology and extractive metallurgy. Therefore, the present work aimed to evaluate the capacity of immobilized biomass of Bacillus subtilis to the biosorption of lanthanum (light REE) and samarium (medium REE), aiming its use in the separation of these elements. The highest percentages of lanthanum (La) and samarium (Sm) biosorption in single-element systems corresponded to 94.4% and 94.9%, respectively, from an initial concentration (iC) of 15 mg/L. In solutions with iC= 100 mg/L, 89.3% of La and 91.9% of Sm were biosorbed. The same behavior can be observed for the bi-elemental solution La + Sm, where 79.9% of La and 88.8% of Sm were biosorbed in solutions of iC= 15 mg/L, and 69.4% of La and 83.4% of Sm were biosorbed in iC= 100 mg/L. The application of the data obtained to the adsorption models of Langmuir and Freundlich showed that the adsorption isotherms obtained for La and Sm in both systems were satisfactory for both models, suggesting the occurrence of monolayer biosorption as well as heterogeneous surface conditions, where both conditions can co-exist under the experimental conditions tested. [ABSTRACT FROM AUTHOR]