Efficient separation of Pd( II ) from HCl media by bifunctional thiomorpholinium‐based ionic liquids

Abstract Bifunctional thiomorpholinium‐based ionic liquids were synthesized for the efficient separation of Pd(II) in HCl media. The presence of S atoms in the six‐membered ring facilitated the efficient extraction of Pd(II), with a remarkable extraction capacity of 212 mg/g. The extraction mechanism involved anion exchange and coordination. Specifically, PdCl 4 2− preferentially combined with positive N atoms in the thiomorpholinium ring through anion exchange by electrostatic attraction, followed by coordination with the functional sulfur atom to form a stable extracted complex. In addition, the effect of the carbon chain length of the cationic substituent on the extraction performance was systematically investigated to further reveal the structure–activity relationship. More importantly, N , N ‐dihexyl‐thiomorpholinium bis(trifluoromethylsulfonyl)imide exhibited excellent Pd(II) selectivity and reusability, retaining 99.4% extraction efficiency after five extraction‐stripping cycles. This study guides the design of ionic liquids‐based extractants and offers a solvent‐free method for the efficient and environmentally friendly separation of Pd(II).