Selective Separation of Uranium, Vanadium, and Rhenium from Sulfuric-Acid Oil-Shale-Ash Leachates by Integrated Ion Exchange and Solvent Extraction

Abstract

An integrated ion-exchange and solvent-extraction route was evaluated for the selective recovery of uranium, vanadium, and rhenium from sulfuric-acid leach liquors produced during processing of metalliferous oil-shale ash. Three commercial anion exchangers (PFA-460, A-600, and AMP) were compared under static and dynamic conditions. The most favorable operating region for selective uranium loading was approximately pH 1. In column tests, PFA-460 exhibited the latest 10% uranium breakthrough (about 150 bed volumes) and the highest dynamic uranium capacity (76.85 g L⁻¹ of resin), whereas A600 and AMP reached 10% breakthrough after about 40 bed volumes. The corresponding resin-phase U:V ratios after 300 bed volumes were 2.7:1, 4.0:1, and 5.3:1, respectively, demonstrating a capacity–selectivity trade-off. Uranium desorption with 0.1–0.2 M HNO₃ in 1 M NH₄NO₃ followed by ammonium-diuranate precipitation produced a concentrate containing >40% U and ≤0.2–0.3% V. Subsequent amine extraction transferred 97.3– 97.9% of rhenium to the organic phase, but molybdenum co-extraction remained significant (19.4–22.8%). Organic-phase washing improved the Re:Mo ratio in the strip solution to approximately 14–21:1. The results define a technically coherent sequence for separating U, Re, and a vanadium-rich Fe–V residue from complex sulfate liquors, while identifying Re/Mo separation as the principal remaining purification challenge.