Extraction and Separation of Selected Platinum-Group and Base Metal Ions from Nitric Acid Solutions Using Thiodiglycolamides (TDGA) as Novel Extractants

Abstract

A new three-structurally related thiodiglycolamides (TDGA), namely, N,N,N′,N′-tetra-n-hexyl-thiodiglycolamide (THTDGA), N,N,N′,N′-tetra-2-ethylhexyl-thiodiglycolamide (TEHTDGA), and N,N,N′,N′-tetra-n-octyl-thiodiglycolamide (TOTDGA) have been synthesized and studied for their extraction behavior towards Pd(II), Pt(IV), Rh(III), Cu(II), Ni(II), and Fe(III) from nitric acid medium. The structure reactivity relationship with extraction of investigated metal ions is studied. The synthesized thiodiglycolamides showed great extractability and selectivity for palladium than the other investigated metal ions. Pd(II) was found to be easily separated from other investigated metal ions in a single extraction step. A systematic investigation has been carried out on the extraction of Pd(II) using both TOTDGA and TEHTDGA. The main extracted species of Pd(II) was found to be Pd(TDGA)₂(NO₃)₂, and IR spectra of the extracted species have been also investigated. The values of thermodynamics functions for the extraction of Pd(II) were calculated.

Keywords:

• thiodiglycolamides
• extraction
• nitric acid, precious and base metal ions

ACKNOWLEDGEMENTS

The authors wish to express their sincere gratitude to Mr. J. Humaida (Lecture of Chemistry-Chemistry Department, Hail University) as well as the Research Laboratories Center (Faculty of Science, Hail University, KSA) for their technical and analysis assistance.