Extractive recovery of palladium(II) from hydrochloric acid solutions with Cyphos®IL 104

Extractive recovery of palladium(II) from a hydrochloric acid solution with quaternary phosphonium salt: trihexyl(tetradecyl)phosphonium bis-(2,4,4-trimethylpentyl)phosphinate (Cyphos®IL 104) as a novel reagent in the presence of toluene has been investigated. Extraction data indicate that Cyphos®IL 104 is a very efficient and fast extractant. The increase in HCl concentration has negative influence on the extraction and 96 and 52% of palladium(II) ions can be effectively extracted with Cyphos®IL 104 from 0.1 and 3.0 M HCl, respectively. The equilibrium of palladium(II) extraction from aqueous 0.1 and 3.0 M HCl with this phosphonium ionic liquid is achieved after 5 min. Extraction of palladium(II) with Cyphos®IL 104 proceeds at the interface according to the anion-exchange mechanism. The best stripping solution from among the studied ones is 0.5 M NH4OH. The feasibility of reuse Cyphos®IL 104 in several cycles of extraction-stripping process was also examined. Increase in temperature from 20 to 70 °C causes a negligible decrease in the palladium(II) extraction. The calculated values of ΔH°, ΔS° and ΔG° evidence that the extraction of palladium(II) with Cyphos®IL 104/toluene mixture is an exothermic reaction both from 0.1 and 3.0 M HCl solutions.