Enrichment of Low Concentration Rare Earths from Leach Solutions of Ion-Adsorption Ores by Bubbling Organic Liquid Membrane Extraction Using N1923

A new bubbling organic liquid membrane extraction using primary amine N1923 at large aqueoustooil phase ratios was suggested to extract and enrich extremely low concentration rare earths from the acidic sulfate leach solutions of ionabsorbing type rare-earth ores. It was revealed that bubbling organic liquid membrane extraction was in fact an interfacial chemical reaction of organic extractant molecules absorbing at the surface of the organic liquid membrane supported by gas bubbles with the target metal ions in the aqueous solutions. Rare earths with a concentration about 100 mg/L can be extracted selectively and enriched efficiently into the organic extractant liquid membrane layer covered on the surface of dispersed gas bubbles. However, Al in leach solutions was not extractable and remained in the raffinates, due to a kinetic nonequilibrium separation behavior of rare earths and Al on the surface of the organic liquid membrane. It was the differences in reaction rate of rare earths and AI with primary amine N1923 that intensified their separation. The separation coefficient of rare earths to Al could reach 44.89. The extraction raffinate, flowing-out from the extraction tower after large-phase ratio extraction, contains aluminum sulfate and can be returned back to displace traditional ammonium sulfate for performing in situ leaching of rare earths from the ion-adsorption ores. The leaching percentage of rare earths was high up to 84.4%. The present work highlights an environmentally friendly and green sustainable new approach to treat ion-adsorbing type rare-earth ores by combining leaching and solvent extraction processes together to solve the problems from ammonia and nitrogen pollution during traditional processes using ammonium sulfate to leach rare-earth ores and ammonium bicarbonate to precipitate rare earths.