Evaluation of novel ligand dithiodiglycolamide (DTDGA) for separation and recovery of palladium from simulated spent catalyst dissolver solution

Novel ligand, namely, N,N,N',N'-tetra-(2-ethylhexyl)-dithiodiglycolamide (DTDGA) has been evaluated for separation and recovery of palladium from simulated spent catalyst dissolver (SSCD) solution. Liquid-liquid batch extraction studies were carried out to understand the influence of various parameters on the extraction behavior of palladium. Extraction equilibrium studies showed near complete extraction of palladium within 5 min. With the increase in hydrochloric acid concentration, the extraction of palladium increased up to 3.0 M HCl and then remained constant on further increase in acidity. Stoichiometry of the extracted species was determined to be PdCI2 center dot DTDGA by mole ratio plot. The effect of various diluents on the extraction of palladium was studied and it was found that there is quantitative uptake in n-paraffinic diluents and the extraction decreases with increase in polarity of diluent. More than 99% of palladium was back extracted in single contact using 0.01 M thiourea in 0.1 M HCl. Extraction studies with SSCD solution showed negligible uptake of Fe, Cr, Ni, and Pt, thus showing very high selectivity and extractability of DTDGA for palladium. (C) 2014 Elsevier B.V. All rights reserved.