Effective UO₂²⁺ removal from aqueous solutions using lichen biomass as a natural and low-cost biosorbent

Highlights: • This study could provide a new material for removal of uranyl. • Langmuir isotherm and pseudo second order kinetic models best decribe uranyl biosorption. • The uranyl biosorption onto Lichen is spontaneous and endothermic. • Lichen is low-cost and efficient biosorbent. - Abstract: The UO₂²⁺ biosorption properties of a lichen, Evernia prunastri, from aqueous solutions were investigated. The widely occurring lichen samples were collected from the forest in Bilecik-Turkey. The UO₂²⁺ biosorption onto lichen was characterized by FT-IR and SEM-EDX analysis techniques before and after biosorption. The effects of the solution pH, biosorbent dosage, UO₂²⁺ concentration, contact time, and temperature on UO₂²⁺ biosorption on lichen sample were studied by using the batch method. The isotherm experimental data were described using isotherm models of Langmuir, Freundlich and Dubinin-Radushkevich. The maximum UO₂²⁺ biosorption capacity of the lichen sample was estimated by the Langmuir equation to be 0.270 mol kg⁻¹. The adsorption energy from the Dubin Radushkevich model was found to be 8.24 kJ mol⁻¹. Kinetic data determined that the biosorption was best described by the pseudo-second-order kinetic model. Thermodynamic findings showed that the biosorption process was endothermic, entropy increased and spontaneous. In conclusion, the lichen appears to be a promising biosorbent for the removal of UO₂²⁺ ions from aqueous solutions because of high biosorption capacity, easy usability, low cost, and high reusability performance.