Palladium(II) Extraction by 4-[(Hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1H-pyrazole from Hydrochloric Acid Solutions

Palladium(II) extraction from hydrochloric acid solutions by 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1H-pyrazole, a new complexing reagent dissolved in toluene or chloroform, was studied. The reagent showed high efficiency in palladium(II) recovery from 0.1-(5-6) \M HCl. Palladium(II) is recovered from 1 \M HCl by the nonprotonated reagent species according to the coordination mechanism to form the extracted compound [PdCl2 mu-L](n) (n > 2). The reagent is coordinated to metal ions via the nitrogen atom and the thioether sulfur atom as shown by H-1 and C-13 NMR spectroscopy. In the temperature range 10-40 degrees C, palladium(II) extraction from 1 M HCl is an endothermic process. The palladium(II) can be quantitatively stripped by a hydrochloric acid solution of thiourea. The reagent (with toluene as diluent) may be recommended for use in palladium(II) concentration from hydrochloric acid solutions and for palladium(II) selective separation from platinum(IV), copper(II), nickel(II), iron(III), and aluminum(III).