Understanding the correlation between extraction and luminescence behavior of Eu(iii) in a biphasic system in the presence of Co-extracting metal ions

Abstract

In this study, the impact of two co-extracting and interfering metal ions in the coordination process of Ln(III) ions using the luminescence spectroscopic technique by taking Eu(III) as the probe was explored for the first time. The solvent extraction route was adopted for the ligation process, and the organic phase composition was a mixture of diglycolamide (DGA) ligand N,N,N′,N′- tetra(ethylhexyl)diglycolamide (T2EHDGA) and tri-n-butyl phosphate (TBP) in n-dodecane (n-DD) medium. Zr(IV) and Pd(II) were considered as co-extracting metal ions along with Eu(III) extraction from nitric acid medium. The varied concentrations of Zr(IV) and Pd(II) in the feed phase led to significant changes in Eu(III) distribution (or luminescence). The extraction factors of Eu(III) decreased in the presence of Zr(IV) while the presence of Pd(II) followed an opposite trend. The presence of TBP in the T2EHDGA/n-DD phase increases the acid (or Eu(III)) concentration in the extracted phase. The emission patterns of Eu(III) in the presence of Zr(IV) and Pd(II) were contradictory to each other, i.e., Zr(IV) enhanced the peak intensity of ⁵D₀ → ⁷F₂ transition, whereas Pd(II) offered a decreased value. The asymmetry ratio (AR) and the lifetime (τ) data of Eu(III) emission both in the aqueous and organic phases with or without Zr(IV) (or Pd(II)) were appraised to comprehend the nature of the Eu(III) complex.