Extraction enhancement and mechanism of light rare-earth elements (III) in chloride medium through adding complexing agent and synergistic effect

ABSTRACT

A binary mixture of two acidic organophosphorus extractants, such as 2-ethylhexylphosphonic mono-2-ethylhexyl ester (HEHEHP) and di-2-ethylhexyl phosphoric acid (D2EHPA), is widely employed for the extraction and separation of light rare earths (LRE) from chloride medium, which displayed pronounced synergistic effect. The water-soluble complexing agent lactic acid (HLac) was added to the aqueous phase to optimize the extraction process. The interactions of LRE with water, HLac and extractants in each phase have been deeply studied to elucidate the extraction behavior. Based on the experiment results, the chemical reactions that occur during extraction are studied in detail, the cation exchange (P-OH bands) and coordination interaction (P = O bands) contribute to LRE extraction were verified.

KEYWORDS:

• Extraction chemistry
• synergistic extraction
• rare earths
• extraction enhancement

Additional information

Funding

The work was supported by the Qingdao Postdoctoral Applied Research Project, Major Basic Research Program of the National Science Foundation of Shandong, China [grant number ZR2018ZB0524]; National Natural Science Foundation of China [grant number 51775289]; Key Research and Development Plan of Shandong, China [No. 2019GGX104097].