Solvent Extraction of Palladium(II) from Aqueous Chloride

ABSTRACT

Solvent extraction of Palladium(II) [Pd(II)] from chloride solution has been investigated by using triphenylphosphine (Ph₃P), triphenylphosphine oxide (Ph₃PO) and triphenylphosphine sulphide (Ph₃PS) as extractants in benzene. Under similar experimental conditions, Ph₃P showed relatively better extraction of Pd(II) compared to the other two extractants. Therefore, detailed investigations on the effects of different parameters on the extraction of palladium by Ph₃P were then carried out. The stripping of the extracted metal species using different stripping agents solutions was investigated and the selective removal of Pd was found to be when using 1 M stabilised thiosulfate solution. Based on the experimental results, an equilibrium model is proposed and the stoichiometry of the extracted species was found to be [Pd(Cl)₂.2Ph₃P]. Thermodynamic parameters including ΔG, ΔH and ΔS for the Pd-Ph3P extraction system were determined. IR spectrum analysis of the extracted complex indicates the direct extraction of Pd as chloride and bonding to phosphorus.