Selective enrichment of palladium from spent automotive catalysts by using a liquid membrane system

A supported liquid membrane (SLM) system for the separation and concentration of palladium from aqueous feed chloride solutions containing SCN- has been developed and characterized by using triisobuthylphosphine sulfide (Cyanex 471) as a carrier. Special attention has been paid to the effect of the organic solvent on the stability of the membrane. Among the different solvents tested in this work, the aliphatic diluent decaline provided the best results in terms of the stability of the LM. Moreover, the influence of chemical parameters such as Cyanex 471 and SCN- concentration on palladium permeability has also been determined for the liquid membrane in flat-sheet configuration. Based on these results, the system was implemented in hollow fiber geometry and the influence of chemical parameters as well as the mode of operation of the HFSLM system has been studied. The selectivity of the proposed LM system was evaluated by using synthetic feed solutions containing Pd(II), Pt(IV) and Rh(III) in chloride media to which small amounts of thiocyanate were added. The results revealed palladium as the only metal transported. This HFSLM system has been successfully applied for the selective recovery and concentration of palladium from solutions obtained from the leaching of spent automotive catalysts. (C) 2003 Elsevier B.V. All rights reserved.