Extractive Mass Transfer of Zr(IV) into a Hydrophobic Ionic Liquid Medium Containing Diglycolamide Extractant: Solvent Extraction and Spectroscopic Analysis.

Abstract

Solvent extraction of Zr(IV) in ionic liquid (IL) medium is less known and Zr(IV) - IL chemistry indeed needs exploration to realize the coordination approach of Zr(IV) in IL phase. In view of this, in the present work, a strongly hydrophobic imidazolium based IL: 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][NTf2]) as the medium containing a diglycolamide (DGA) extractant: N,N,N',N'-tetra-n-octyldiglycolamide (TODGA) was opted to understand the extraction behavior of Zr(IV) from nitric acid medium. Different experimental parameters such as the concentration of initial nitric acid, initial feed metal concentration, equilibration time and ligand concentration were tuned to unravel the extraction efficiency of the proposed IL phase towards Zr(IV). The extraction scenario was completely dependent on the hydrophobicity of IL diluent and increasing extraction trend with an increase in feed acidity along with the coordination of two TODGA molecules ensured Zr(IV) - complex formation in a neutral solvation mechanistic pathway. The extraction trend of Zr(IV) was compared with molecular diluent (n-dodecane (n-DD)) containing TODGA and a phase modifier: N,N-dihexyloctanamide (DHOA). The coordination aspect of Zr(IV) with ligand in IL phase was ascertained spectroscopically to validate Zr(IV) loading in IL phase. Thermodynamics of Zr(IV) extraction revealed the nature of the extraction process and the complex formation.