The study on extraction behavior of [N1888][P507] and TRPO for heavy rare earths.

• [RE(H 2 O) 9 3+][3Cl-] was stable solvation model in water. • [N1888][P507] as extractants was selected from 80 ionic liquids using different indicators. • The extraction and stripping property of the mixture of [N1888][P507] and TRPO were studied. • The TRPO ability to form third phase decreased with ratio of [TRPO]and[N1888][P507] increasing. • 96.3 % Tb3+ could be stripped from the organic phase to the aqueous phase after five times stripping processes. Ionic liquids were extensively used in many extraction and separation processes for metal ions because of excellent dissolving and selecting ability. The COSMO-RS method was applied for selecting suitable ionic liquid from 80 kinds of ionic liquids. Hydrophilicity, solvent solubility, distribution ratio were considered as important factors for selecting suitable ionic liquids. [N1888][P507] was suitable ionic liquid for extracting and separating heavy rare earths. A solvent extraction system containing ionic liquid [N1888][P507] and molecular extractant TRPO to separate heavy rare earths was studied. The results showed that the mixture of the [N1888][P507] and TRPO contributed to high extractabilities and selectivities of heavy rare earths. The abilities to form third phase and product emulsification phenomenon decreased with the concentration ratio of TRPO and [N1888][P507] increasing. The extraction mechanism of HREEs was deduced as ion association. The quantitative stripping of HREEs from loaded organic phase could be achieved with deionized water and low concentration of hydrochloric acid. The article showed that the mixture of [N1888][P507] and TRPO might be an effective and environmentally friendly extractant for extraction and separation of heavy rare earths. [ABSTRACT FROM AUTHOR]