Evaluation of unsymmetrical dithiodiglycolamide as novel extractant for application in selective separation of palladium(II) from aqueous solutions

Abstract

A novel unsymmetrical multidentate ligand namely; N,N'-dimetyl-N,N'-didecyldithiodiglycolamide (DMD³TDGA) was synthesized and used as agent for the selective extraction of palladium(II) from hydrochloric acid solutions. A systematic investigation was carried out on the extraction of Pd(II) using DMD³TDGA. The quantitative extraction of Pd(II) with DMD³TDGA in n-dodecane is observed at ~4 M HCl. The main extracted species of Pd(II) is PdC_l2. DMD³TDGA and IR spectra of the extracted species were investigated. The extraction of palladium(II) from various concentrations of hydrochloric acid solutions in the presence of metal ions, such as Pt(IV), Rh(III), Cr(II), Ni(II), Fe(III), Nd(III), Zr(II), and Mn(II) was carried. DMD³TDGA showed very high selectivity and extractability for Pd(II). Quantitative back extraction of Pd(II) was obtained in single contact using thiourea solution. The results obtained indicated that, excellent separation of Pd(II) from the investigated metal ions can be achieved. Five successive cycles of extraction/back-extraction, indicating excellent stability and re-utilization of this new extractant can be used for selective separation of Pd(II) from other elements in hydrochloric acid medium.