Separation of palladium(Pd)and platinum(Pt)by solvent extraction is difficult because of their extremely similar physicochemical properties.Development of new extractants with a high extraction efficiency and excellent separation selectivity is the primary focus for enhancing the separation of Pd and Pt by solvent extraction.In this study,a new extractant,2-((2-methoxyethyl)thio)-lH-ben-zimidazole(MOBI),which contains N,S,and O atoms,was synthesized and used to separate Pd(II)and Pt(IV)from a hydrochloric acid aqueous solution.The experi-mental results revealed that Pd(II)and Pt(IV)were effec-tively separated under the optimal conditions:MOBI concentration of 0.005 mol·L-1,HC1 concentration of 0.2 mol?L-l,organic/aqueous(O/A)phase ratio of 1.0,and contact time of 15 min.The separation coefficient between Pd(II)and Pt(IV)was 1246.40,which indicates that MOBI has a higher selectivity for Pd(II)than Pt(IV).In addition,the mechanism of coordination between Pd(II)and MOBI was demonstrated through the slope method,Fourier transform infrared spectroscopy(FTIR),hydrogen-1 nuclear magnetic resonance spectroscopy(1H NMR),and carbon-13 nuclear magnetic resonance spectroscopy(13C NMR).The results revealed that MOBI could coordinate with Pd(II)via the N atom in the benzimidazole ring of MOBI molecules to form[Pd(MOBI)2Cl2](O).