Application of Bifunctional Ionic Liquid Extractants [A336][CA-12] and [A336][CA-100] to the Lanthanum Extraction and Separation from Rare Earths in the Chloride Medium

In this Article, bifunctional ionic liquid extractants (Bif-ILEs) tricaprylmethylammonium sec-octylphenoxy acetic acid ([A366][CA-12]) and tricaprylmethylammonium sec-nonylphenoxy acetic acid ([A336][CA-100]) used for the rare earths (REs) extraction from the chloride medium have been investigated. The effects of extractants concentration, equilibrium pH of aqueous phase, salt concentration, temperature, etc., were discussed. The results show that the extraction ability of [A336][CA-12] and [A336][CA-100] is higher than that of the conventional extractants sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100), tri-n-butyl phosphate (TBP), and di-(1-metylheptyl)methyl phosphate (P350) under the same conditions. Furthermore, in the [A336][CA-12] system, the separation factors (beta) between La(III) and other REs(III) are higher than 6.0, which indicates that [A336][CA-12] would be suitable for the La(III) extraction and separation. The extraction mechanism is also proposed, and there is a similar extraction tendency in both the [A336] [CA-12] and the [A336][CA-100] systems. The loaded organic phase is easy to strip; more than 95% La(III) could be stripped from the loaded organic phase when the stripping acidity is higher than 0.03 M. The recycling experiments also indicate that the two extraction systems could be recycled without loss of the extraction efficiency.