Production of Pr + Nd fraction from phosphogypsum by resin-in-leach and dynamic anion exchange separation

Industrial phosphogypsum (PG), a byproduct from phosphoric acid production, is an attractive source of rare earth elements (REEs). In this work, a complete REE recovery process starting from authentic industrial waste PG is demonstrated. Selective extraction of REEs from calcium-containing matrix was achieved using a chelating resin in a resin-in-leach process (RIL). By combining HCl washing with alkaline methylglycinediacetic acid (MGDA) regeneration of the loaded resin, a high-purity (98.3%) Ca-free mixture was obtained. The resulting MGDA–REE mixture contained a high proportion of Ce (∼ 45%) relative to the other REEs. Cerium(III) was selectively removed by oxidation with H 2 O 2 to precipitate Ce(OH) 4 . The concurrent effect of the oxidizer on MGDA was also studied to evaluate ligand stability. To enhance the purity of individual MGDA-REE complexes, strong-base anion (SBA) resin combined with dilute HCl elution was used for chromatographic separation. The separation was based on differences in the stabilities of the complexes. A two-step separation process was introduced to obtain the main product, a Pr + Nd mixture. After the first separation step, the purity of Pr + Nd product fraction reached 87.9%. A second step further improved the purity, yielding a final Pr + Nd fraction with purity of 96.1%. Additionally, a La-containing fraction with a purity of 74.4% was obtained as a secondary product. These products can subsequently be converted into the corresponding oxides via oxalate precipitation followed by calcination.