A novel MWCNTs-P204/TBP membrane with dual-site extraction function for continuous selective separate neodymium by electrochemically switched ion membrane extraction

A novel carbon nanotube combining bis(2-ethylhexyl) phosphate/tributyl phosphate membrane (MWCNTs-P204/TBP membrane) with dual-site extraction function was obtained by constructing a dense P204/TBP liquid phase extraction layer in a 3D porous MWCNTs membrane and proposed a “chemical-electrochemical dual site extraction” mechanism that consists both the chemical extraction dominated by proton exchange and electrochemical extraction dominated by electrochemical complexation pathways. The membrane was applied with an electrochemically switched ion membrane extraction (ESIME) process to realize continuous selective extraction/stripping of Nd 3+ . Model calculation and DFT simulations indicate that the mass transfer rate of Nd 3+ in the feed phase is 7.45 times higher than that of Dy 3+ under the action of the electric field, and the chemical softness of P204 and Nd 3+ extraction complex 15.15 is higher than that of Dy 3+ 2.73, the coupling effect of cell voltage and pulse potential can effectively facilitate the selective extraction and stripping of Nd 3+ by MWCNTs-P204/TBP membrane. The Nd 3+ flux as high as 7.31 μmol·m −2 ·s −1 with a separation factor β Nd 3+ /Dy 3+ of 9.56 was achieved even after five times enrichments. It manifested that the ESIME system with MWCNs-P204/TBP membrane provides a scalable process for the continuous selective separation of Nd 3+ from waste permanent magnets.