Recycling of Palladium and Selected Metal Ions from Simulated Spent Catalysis Waste Solution Using Novel Dithiodiglycolamides Derivatives

The present study focusing on design and evaluation of series of eight new structurally related dithiodiglycolamides (DTDGA) as a novel promising solvent extraction reagents. The influence of the nature of the alkyl chain on the distribution ratio of Pd(II) was investigated. Both N, N-di-hexyl-N′, N′-di-octyldithiodiglycolamide (DHDODTDGA) and N, N-di(2-ethylhexyl)-N′, N′-dioctyldithiodiglycolamide (DEHDODTDGA) were chosen and applied to perform the selective recovery and separation of Pd(II) from certain commonly associated elements such as Pt(IV), Rh(III), Fe(III), Cr(II), Mn(II), Zr(II), and Ni(II) contained in hydrochloric acid solutions using n-dodecane as diluent. A systematic investigation has been carried to understand the extraction behavior of Pd(II) using the synthesized extradant. The extraction equilibrium of Pd(II) was obtained within 3–4 min. The investigated extractants showed quantitative extraction of Pd(II) at ～ 4 M HCl. The main extracted species of Pd(II) at 3.5 M HCl is Pd.DTDGA and IR spectra of the extracted species have been also studied. The other investigated metals ions were found poorly extracted under the same extraction contortions. Quantitative back-extraction of Pd(II) in the organic phase was obtained in single contact using thiourea solution. The obtained results make the novel synthesized ligands a promising candidates for selective recovery and separation of Pd(II) from spent catalyst dissolver (SSCD) solution.