Solvent Extraction of Palladium(II) from Aqueous Chloride Media with 1,2-Bis(tert-hexylthio)ethane

Abstract

Abstract The extraction equilibrium and kinetics of palladium(II) extraction from an aqueous chloride media with 1,2-bis(tert-hexylthio)ethane (mixture), abbreviated as t-BHTE and denoted by B, in toluene were studied at 303 K. Palladium(II) was extracted as a 1:1 Pd : extractant complex, [PdCl2B]. The partition coefficient of this extractant was evaluated as Kd=5.5×104 for hydrochloric acid and Kd=2.5×104 for an aqueous ammonium chloride solution. The results of kinetic experiments were quantitatively explained in terms of a reaction scheme in which parallel reactions of t-BHTE with [PdCl3]− and [PdCl4]2− in an aqueous phase were the rate-determining steps: [PdCl3]−aq.+Baq.\xrightarrowk1[PdCl2B]aq.+Cl−aq. [PdCl4]2−aq.+Baq.\xrightarrowk2[PdCl2B]aq.+2Cl−aq. The reaction rate constants for the above were evaluated as k1=6.4×104 dm3 mol−1 s−1 and k2=2.6×102 dm3 mol−1 s−1 for extraction from an aqueous ammonium chloride solution, and k1=6.7×104 dm3 mol−1 s−1 and k2=3.2×102 dm3 mol−1 s−1 from a hydrochloric acid solution.