2026 Pereira Rare earth extraction from columbite residue

Rare earth elements (REEs), the 15 lanthanides plus yttrium (Y) and scandium (Sc), are critical metals for energy transition and digital technologies. They are essential for permanent magnets, catalysts, phosphors, and advanced ceramics. Secondary sources such as mining residues often contain REEs along with impurities such as iron (Fe), thorium (Th), and uranium (U), which complicate selective recovery. In this context, the present work focuses on evaluating the selectivity and efficiency of different extractant systems for REEs in a real columbite leachate residue. The precipitation step was evaluated using calcium oxide (CaO), sodium hydroxide (NaOH), and ammonium hydroxide (NH4OH) at pH 1.0 to assess initial impurity removal. Five commercial extractants with distinct functional groups—bis(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A), bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), a mixture of trialkylphosphine oxides (Cyanex 923), and tri-n-butyl phosphate (TBP)—were compared by varying pH, extractant concentration, and the aqueous-to-organic ratio. Results indicated that D2EHPA exhibited the best overall performance, achieving high extraction rates for heavy and light REEs, albeit with coextraction of impurities.