Extraction and recovery of cerium(IV) and fluorine(I) from sulfuric solutions using bifunctional ionic liquid extractants

The extraction of cerium(IV) (Ce(IV)), fluorin (F−) and Ce(IV)–F mixture solution from sulfuric acid medium using bifunctional ionic liquid extractants (Bif-ILEs) [trialkylmethylammonium][di-(2-ethylhexyl)orthophosphinate] ([A336][P507]), [trialkylmethylammonium][di-2-ethylhexylphosphinate] ([A336][P204]) and [trialkylmethylammonium][bis 2,4,4-trimethylpentylphosphinate] ([A336][C272]) in n-heptane have been investigated in this report. The effect of H2SO4 concentration, extractant concentration and salting-out agent concentration has been investigated. The thermodynamic parameters have been determined, showing that the extraction was exothermic. The extraction mechanism has been obtained. The comparison for the extraction of Ce(IV), Ce(IV) in Ce(IV)–F mixture solution, cerium(III) (Ce(III)) and thorium(IV) (Th(IV)) has been investigated and the extraction efficiency order followed as: Ce(IV) > Th(IV) > Ce(III). Ce(IV) in Ce(IV)–F mixture solution was extracted in the form of CeF3+. The highest separation factor (β) values of Ce(IV)/Ce(III) and CeF3+/Ce(III) were 3.32 × 103 and 2.58 × 103 in the [A336][P507] extraction system, 7.27 × 102 and 6.94 × 102 in the [A336][P204] extraction system, and 1.84 × 102 and 2.75 × 102 in the [A336][C272] extraction system, respectively, which indicated that Ce(IV) and Ce(IV) in Ce(IV)–F mixture solution could be separated from Ce(III) effectively.

► The Bif-ILEs were first used for Ce(IV) and Ce(IV)–F− extraction from sulfuric solution.
► The extraction efficiency order followed as: Ce(IV) > Th(IV) > Ce(III).
► The Bif-ILEs have good extraction ability for Ce(IV) under lower acidity.