Lanthanide ion processing from monazite based on magnetic nanohydrometallurgy

A systematic work has been performed for the separation of the lanthanide elements from monazite mineral using magnetic nanohydrometallurgy. The process was based on DTPA (diethylenetriaminepentaacetic acid) functionalized Fe3O4 superparamagnetic nanoparticles as the active species for carrying out the magnetic extraction of the lanthanide ions in aqueous solution, at pH?6. The process was monitored by means of X-ray fluorescence (EDXRF) techniques, and the corresponding Langmuir isotherms were carefully elaborated, allowing to evaluate the equilibrium (affinity) constants involved. The results obtained for La3+, Pr3+, Nd3+, Sm3+, Gd3+ and Dy3+ ions followed the trends dictated by the lanthanide ion contraction. In the process, the elements are reversibly captured and released from the magnetically confined nanoparticles after applying a mild acid treatment (pH?2). Their chemical separation based on their relative affinity constants, can be performed by applying successive magnetic extraction/releasing cycles in aqueous solution, at room temperature, using the same reactor, dispensing the use of organic solvents and more intensive chemical processing.