Biosorption of lanthanum and samarium by chemically modified free Bacillus subtilis cells

Previous studies showed that Bacillus subtilis possessed high physiological activity in industrial waste treatment as a biosorbent for recovery metals, and in this study, the sorption capacity for both La³⁺ and Sm³⁺ was demonstrated. The effects of lanthanide concentration and contact time were tested to acid and alkali pre-treated cells. Very high levels of removal, reaching up to 99% were obtained for both lanthanide ions. Langmuir isotherm model was applied to describe the adsorption isotherm and indicated a better correlation with experimental data R² = 0.84 for La³⁺ using sodium hydroxide pre-treated free cells and R² = 0.73 for Sm³⁺ to acid pre-treated B. subtilis cells as biosorbents. Results of this study indicated that chemically modified B. subtilis cells are a very good candidate for the removal of light rare-earth elements from aquatic environments. The process is feasible, reliable, and eco-friendly.