Studies on the Roles of Different Components in Cyanex 302 for Rare Earth Ions Extraction and Separation

Abstract

In this paper, the extractabilities of Cyanex 302 and purified Cyanex 302 (hereafter HBTMPTP or HA) in heptane have been compared by extracting the scandium, yttrium, lanthanum, and gadolinium from hydrochloric acid solutions. The roles of the different components in Cyanex 302 on lanthanum extraction have been analyzed. The result demonstrates that the Cyanex 302 has a higher extractability than HBTMPTP, which perhaps originates from the interaction among the components in Cyanex 302. Especially for R₃PO, obviously synergistic effect can be observed in the lower pH range and extraction mechanism of lanthanum using the mixture of HBTMPTP and TOPO has been deduced to be:

where (HA)₂ and B denote the dimeric form of HBTMPTP and TOPO, respectively. At the same time, the separation abilities of Cyanex 302 and HBTMPTP on the rare earth elements have been compared. Also, the effect of temperature on the extraction with Cyaenx 302, HBTMPTP and the mixture of HBTMPTP and TOPO has also been discussed with thermodynamic functions ΔH, ΔS, and ΔG calculated.

Keywords:

• Cyanex 302
• HBTMPTP
• TOPO
• synergistic extraction
• rare earths
• separation

Acknowledgements

The authors wish to thank Cytec Canada Inc. for supplying Cyanex 302. The project was supported by the State Key Project of the Foundation Research (2004CB719506) and National Natural Science Foundation of China (20371046).