Palladium Recovery by Reactive Precipitation using a Cyanex 301‐Based Stable Emulsion

Abstract

Cyanex 301^®, di(2,4,4‐trimethylpentyl) dithiophosphinic acid, has been combined with gelatin and alginate to prepare a stable emulsion that can be used for the reactive precipitation of palladium (metal reaction with the sulfur functional group of Cyanex 301). The ionotropic gelation of alginate leads to material precipitation. The process has been successfully tested for Pd binding from 0.1–5 M HCl solutions. The maximum binding capacity was found to be close to 350 mg Pd g⁻¹ Cyanex 301. A 1∶1 stoichiometric relation between Cyanex 301 and Pd has been identified. Extractant dependency plots showed that the ligand in the Pd‐Cyanex 301 complex can also have a solvation number higher than one. Palladium uptake is not significantly affected by the presence of competing metals such as Cu, Ni, Zn, or Pt. Quantitative stripping of Pd from the precipitated bio‐polymer could not be achieved.

Keywords:

• Palladium
• Cyanex 301
• alginate
• gelatin
• emulsion
• precipitation

Acknowledgments

The authors thank Cytec (Canada) for the gift of the Cyanex 301 sample used in this work. The part of this work performed at ANL was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, under contract DE‐AC02‐06CH11357.