Enhancing extraction of rare earth elements from NdFeB acid leachate using pulsed sieve-disc and doughnut column

The pulse disc and doughnut columns (PDDC) require high energy input when dealing with systems where the dispersed phase is difficult to break, which limits its application. To address this, a novel extraction column, pulsed sieve − disc and doughnut column (PSDDC) was designed. The hydrodynamics and extraction performance in the PSDDC were investigated systematically using neodymium-iron-boron (NdFeB) magnet scraps acid leachate–PC-88A extractant system. The results indicated that inducing sieve plates effectively reduced droplet size at a mild pulse intensity. Furthermore, compared with the required pulse intensity of 1.5 cm/s to shift operation zone from mixer-settler zone to emulsion zone in PDDC, PSDDC only required 1.0 cm/s. In the mixer-settler zone, the dispersed phase holdup ( x d ) values were comparable in both columns, while in the emulsion zone the x d values in PSDDC were higher than those in PDDC. At a medium pulse intensity of 1.5 cm/s, the extraction performance of rare earth elements (REEs) in the PSDDC was enhanced, with an extraction efficiency of 65.19 %, representing a 6-fold increase over the PDDC. Additionally, new correlations were established for the Sauter mean droplet size ( d 32 ), x d and mass transfer coefficients of dispersed phase ( K od ) in PSDDC, yielding average relative residual errors ( AARE s) of 9.43 %, 10.96 %, and 10.04 %, respectively. Briefly, compared with PDDC, PSDDC exhibited excellent extraction performance for REEs in the NdFeB acid leachate–PC-88A system.