High-purity rubidium salts production from high-alkalinity and high-impurity solution via solvent extraction

Rubidium and its compounds are widely utilized in advanced technologies. Alkaline leaching is an effective approach for rubidium extraction from ores. However, the leachate is characterized by high alkalinity and potassium concentrations, which complicates the recovery of rubidium. This study utilizes t-BAMBP as an extractant to achieve efficient extraction and separation of rubidium from alkaline leachates, ultimately yielding high-purity rubidium salt products. Firstly, key parameters including diluent type, NaOH concentration, t-BAMBP concentration, mixing time, and phase ratio were systematically optimized. A four-stage countercurrent extraction validation achieved 99.3 % Rb extraction, with residual Rb concentration of 0.002 g/L in the raffinate. ¹H NMR and FT-IR analyses revealed that the extraction mechanism was cation exchange between Rb⁺ and H⁺ on the phenolic hydroxyl group in t-BAMBP. Subsequently, HCl was utilized as both the scrubbing and stripping agent. After a nine-stage countercurrent scrubbing simulation, the potassium concentration in the loaded organic phase decreased to 0.004 g/L, achieving an efficient separation of rubidium and potassium. Ultimately, high-purity RbCl and Rb₂CO₃ were synthesized, both meeting the purity requirement of 99.5 %.