Extraction, separation and recovery of Palladium and Platinum by a kinetic method combined with ultrafiltration

Abstract

A method is presented allowing separation of palladium from platinum based on the different kineticlability of the two metals. These are let to react with PADA (trans-pyridine-2-azo-p-dimethylaniline) inthe presence of SDS micelles. The kinetic study of the PADA binding to Pd(II) and Pt(II), both in form ofchlorocomplexes, shows that the reactivity of PdCl42−is about 4 × 103-fold higher than that of PtCl42−.The Pd(II)–PADA complex is completely formed in about 30 min and adsorbed on the micelle surface. Inthis lapse of time less than 2% of Pt(II) is complexed. The separation of the two metals is then accom-plished by ultrafiltration. With this procedure 98% of platinum can be recovered in the filtrate. Palladium,present in the retentate, is then recovered using a stripping agent and a multi-step ultrafiltration proce-dure. The most efficient among the stripping reagents tested is HCl 0.05 M (yield 90% after three steps).The extraction yield is independent of the concentration of the SDS micelles ([SDS] = 0.01–0.04 M), thusallowing low concentrations of surfactant to be used with excellent yields.© 2013 Elsevier B.V. All rights reserve