Super-enrichment of ultra-low concentration rhenium via synergistic co-flocculation precipitation using CTAB and ferric salt hydrolysis micelles

Super-enrichment and recovery of associated Rhenium (Re) in sandstone-type uranium deposits is challenging due to its sparse distribution and ultra-low contents in raw ores. Conventional industrial processes are extremely difficult to achieve economic recovery of Re with a concentration below 0.1 mg/L from in-situ leaching solutions of sandstone-type uranium deposits. This study proposes a novel approach for achieving super-enrichment ultralow concentration of Re using a synergistic co-flocculation precipitation system composed of cetyltrimethylammonium-bromide (CTAB) and ferric salt (FeCl3) hydrolysis micelles. Experimental results reveal that the enriched content of Re in the co-flocculation precipitates is as high as 503 g/t, nearly 3353 times higher than that in the in-situ leaching solutions. The synergistic precipitation percentage of Re can reach more than 60%, which is larger than the sum of using CTAB micellar flocculation (30.16%) and FeCl3 hydrolysis micellar flocculation (5.43%) separately. Furthermore, the synergistic co-flocculation and precipitation mechanism of Re is examined by SEM, turbidity, Fourier transform infrared spectroscopy, Zeta potential analysis, and DTF calculations. Results demonstrate that the ReO4- anions first form ion associations with CTA+ cations through electrostatic force, which are subsequently captured to forms insoluble co-flocculating precipitate via weak intermolecular hydrogen bond force between Fe(OH)3 and ReO4- , which promotes the super-enrichment of the ultra-low concentration Re. In summary, this process presents great potential for the efficient recovery Re from a large amounts of sandstone-type uranium deposits leaching solution, and provides new insights into the enhancement mechanism of synergistic co-flocculation precipitation.