N, N, N′, N′-tetra(2-ethylhexyl) thiodiglycolamide T(2EH)TDGA: A novel ligand for the extraction of palladium from high level liquid waste (HLLW)

Abstract

A novel neutral multidentate ligand N , N , N ′, N ′-tetra(2-ethylhexyl) thiodiglycolamide T(2EH)TDGA was synthesized and examined for the extraction of palladium from nitric acid medium. Extraction equilibrium studies showed that almost complete extraction of palladium was obtained within 5 min. The influence of nitric acid, nitrate ion and T(2EH)TDGA concentration on the distribution of palladium has been investigated. With the increase in nitric acid/nitrate ion concentration, increase in extraction of palladium was observed. Stoichiometry of the extracted species was found to be Pd(NO 3 ) 2 ·2T(2EH)TDGA by slope analysis method. Loading studies with 10 −3 M T(2EH)TDGA/ n -dodecane show maximum uptake of 5.44×10 −4 M palladium thus conforming to above stoichiometry of metal to ligand. Acid uptake studies have shown that 1:1 stoichiometry exists between T(2EH)TDGA and HNO 3 at nitric acid concentration above 3.5 M. The effect of various diluents on the extraction of palladium was studied and it was found that there is quantitative uptake irrespective of the nature of diluents. More than 99% of palladium was back extracted in single contact using 0.01 M thiourea in 0.1 M nitric acid. Extraction studies with HLLW elements showed negligible uptake of U, Am, Eu, Sr, Cs and Ru.