A
NEW
BUBBLING
EXTRACTION
TOWER:
TOWARDS
ENRICHMENT AND RECOVERY OF RARE EARTHS WITH
EXTREMELY
LOW
CONCENTRATIONS
IN
MINERAL
LEACHING SOLUTIONS
Kun Huang* and Huizhou Liu
Key Laboratory of Green Process and Engineering, Institute of Process Engineering,
Chinese Academy of Sciences, Beijing 100190, P.R. China
*Corresponding author: Prof. Dr. Kun Huang, Email: khuang@ipe.ac.cn, Tel: 86-1082544910, Fax: 86-10-62554264
ABSTRACT
Enrichment and recovery of rare earths with extremely low concentrations in mineral
leaching solutions by traditional solvent extraction technologies are difficult and not
economic. In present work, a new bubbling extraction tower towards extraction and
enrichment of rare earths from the leaching solutions of weathered crust elutiondeposited rare-earth ores by liquid-liquid solvent extraction at extremely large aqueousto-oil phase ratios is proposed. The aim of structural design for such a kind of largephase-ratio extraction tower is to disperse and cover small volume of organic
extractants onto surface of gas bubbles to form a layer of organic liquid membrane.
Extraction was in fact conducted on the organic liquid membrane layer on the surface
of those dispersed oil bubbles when they pass through the aqueous solutions in tower.
Therefore, rare-earth ions can be efficiently extracted and enriched into small volume
of organic extractants with higher enrichment factors. The height of the large-phaseratio extraction tower can be calculated based upon plug-flow model and dual resistance
model. Aqueous-to-oil operation phase ratios have close relationship with gas
containment ratios in tower, and can be calculated when tower diameter is given.
Dispersion characters of organic liquid membrane on the surface of gas bubbles is a
main concern in current calculation. Experimental results in pilot tests confirmed the
rationality of proposed calculation models and revealed that enrichment and recovery
of low content of heavy rare earths are feasible from the mineral leaching solutions
obtained from Jiangxi ores in South China. Aqueous-to-oil operation phase ratios could
reach more than 600:1, and the enrichment factors of rare-earth ions are extremely high.
The present works provide a scientific basis for structural design of the suggested new
bubbling extraction tower, and it is important for future optimization, scale-up and
industrial application.
KEYWORDS
Rare earths, Enrichment, Low concentration, Solvent Extraction, Large-phase-ratio