Synthesis of Et-Ph-BCTABipy and Its Extraction Properties for Pd²⁺

In this work, a phenanthroline based tetradentate neutral sulfur-containing ligand, N,N′-diethyl-N,N′-diphenyl-［2,2′-bipyridine］-6,6′-bis(carbothioamide)(Et-Ph-BCTABipy) was synthesized and characterized by ¹³C NMR and ¹H NMR. The effects of phase contact time, concentration of extractant, and initial concentration of HNO₃ and Pd²⁺ in aqueous phase on the extraction performance of Et-Ph-BCTABipy were studied, and the complex composition of Et-Ph-BCTABipy with Pd²⁺ was determined by molar ratio method. At the same time, the extraction selectivity of Et-Ph-BCTABipy to Pd²⁺ was also studied in the coexistence system of Ln(Ⅲ) and Pd²⁺. The results show that Et-Ph-BCTABipy has strong extraction performance and high extraction selectivity for Pd²⁺ in HNO₃ system. During the extraction process, Et-Ph-BCTABipy combines with Pd²⁺ in a ratio of 1∶2, and its extraction equilibrium coefficient is K_ex=3.42×10⁶.