Neodymium and samarium recovery by magnetic nano-hydroxyapatite

The removal and recovery of lanthanides has become important because of their wide applications in industry and also in environmental protection. The necessity for these elements requires the selective and effective separation technique. In this study, batch adsorption method as a green technology has been investigated for removal and recovery of Nd and Sm using magnetic nano-hydroxyapatite adsorbent (MNHA). According to results, the maximum adsorption capacities of Nd and Sm were calculated as 323 and 370 mg/g at optimum pH 5.5, respectively. Different types of adsorption isotherms and kinetic models were used to describe the Nd and Sm adsorption behavior, and the experimental results fitted Langmuir model and the pseudo-second-order kinetic models well. The adsorption of Nd and Sm was found as endothermic and spontaneous process with respect to obtained thermodynamic parameters. Recovery of adsorbed lanthanides and reusability of adsorbent was tested. Possible adsorption mechanisms were also discussed. The proposed adsorbent, MNHA has good adsorption ability and high sorption capacity for Nd and Sm with a chemisorption mechanism.