2-Octylaminopyridine assisted solvent extraction system for selective separation of palladium(ii) ion-pair complex from synthetic mixtures and real samples

Abstract

Herein, 2-octylaminopyridine (2-OAP) amine is used in the liquid–liquid extraction of palladium(II) from aqueous salicylate media. It is found that pH does not affect the metal extraction process in the pH range of 1.8–2.4. Palladium(II) complex formation was verified by a log–log plot, whereas from the slope analysis, the ion pair complex stoichiometry 1 : 1 (metal : ligand) and 1 : 3 (metal : acid) was confirmed. The extraction system was optimized for the choice of diluent (xylene) as well as for the effective stripping agent (5.0 M ammonia). The selectivity for palladium(II) was found to be maintained when the organic phase (0.03 M 2-OAP in xylene) is used to extract the palladium(II). The extraction saturation capacity of palladium(II) was determined from 0.02 M sodium salicylate solution with 10 mL 0.03 M 2-OAP, and its experimental value exceeds 2.5 mg under the experimental conditions. Stripping of palladium(II) from the loaded organic phase was performed with 5.0 M ammonia. The extraction with varying parameters like equilibrium time, temperature, diluents, concentration of extractant, loading capacity, regeneration power and stability of extraction was also studied. The extraction behavior of associated metals, namely, noble metals and base metals, has been investigated, and the conditions for binary separation involving these metal ions have been optimized. Based on the extraction protocol, palladium(II) has been recovered from real samples.