Selective separation of rare earth ions from aqueous solution using functionalized magnetite nanoparticles: kinetic and thermodynamic studies

Abstract Separation of rare earth ions (RE 3+ ) from aqueous solution is a tricky problem due to their physico-chemical similarities of properties. In this study, we investigate the influence of the functionalized ligands on the adsorption efficiency and selective adsorption of La 3+ , Nd 3+ , Gd 3+ and Y 3+ from aqueous solution using Magnetite (Fe 3 O 4 ) nanoparticles (NPs) functionalized with citric acid (CA@Fe 3 O 4 NPs) or l -cysteine (Cys@Fe 3 O 4 NPs). The microstructure, thermal behavior and surface functionalization of the synthesized nanoparticles were studied. The general adsorption capacity of Cys@Fe 3 O 4 NPs was found to be high (98 mg g −1 ) in comparison to CA@Fe 3 O 4 NPs (52 mg g −1 ) at neutral pH 7.0. The adsorption kinetic studies revealed that the adsorption of RE 3+ ions follows a pseudo second-order model and the adsorption equilibrium data fits well to the Langmuir isotherm. Thermodynamic studies imply that the adsorption process was endothermic and spontaneous in nature. Controlled desorption within 30 min of the adsorbed RE 3+ ions from both Cys@Fe 3 O 4 NPs and CA@Fe 3 O 4 NPs was achieved with 0.5 M HNO 3 . Furthermore, Cys@Fe 3 O 4 NPs exhibited a higher separation factor (SF) in the separation of Gd 3+ /La 3+ , Gd 3+ /Nd 3+ , Gd 3+ /Y 3+ ions compared to CA@Fe 3 O 4 NPs.