Removal of rare earth elements by MnFe2O4 based mesoporous adsorbents: Synthesis, isotherms, kinetics, thermodynamics

Abstract As an important strategic resource, rare earth elements are widely used in cutting-edge industries, and the resulting environmental pollution and resource recycling problems have also attracted widespread attention. In this paper, two new adsorbents, MnFe2O4-Al2O3 and MnFe2O4@SiO2-Chitosan (MnFe2O4@SiO2-CS) mesoporous magnetic microsphere, were successfully prepared with spinel MnFe2O4 as the main component, and they were employed in the adsorption of REEs. Characterized methods, such as VSM, SEM, XRD, FTIR, and BET were applied to analyze the morphologies as well as the structures of the new materials. The adsorption isotherms, kinetics, and thermodynamics were studied to determine the adsorption mechanism and maximum adsorption capacity of the prepared adsorbents for REEs. Under the optimal conditions (pH 7.0 and temperature = 298 K), the maximum adsorption capacity of MnFe2O4@SiO2-CS to La3+ and Ce3+ were 1030 and 1020 mg/g, respectively. Moreover, kinetic studies indicate that the adsorption reactions can reach equilibrium within 30 min. The results of the desorption regeneration experiments indicate that the prepared adsorbents have good recycling properties and can be reused. In summary, the advantages of low cost, high adsorption efficiency, magnetic separation and reusability indicate that MnFe2O4-Al2O3 and MnFe2O4@SiO2-CS have great application prospects for adsorbing REEs.